Cholinergic/Adrenergic drugs — MCQs

Q: A mother reports that her daughter ingested a substance in an unknown dose. The girl presents with hypertension, tachycardia, mydriasis, and hyperthermia. What is the most likely substance?

Cocaine. ***Cocaine*** - The presented symptoms of **hypertension, tachycardia, mydriasis, and hyperthermia** are characteristic of a **sympathomimetic toxidrome**, frequently caused by cocaine overdose. - Cocaine acts as a **norepinephrine-dopamine-serotonin reuptake inhibitor**, leading to excessive stimulation of the central and peripheral nervous systems. *Heroin* - Heroin is an **opioid**, and overdose generally presents with **respiratory depression, bradycardia, miosis (pinpoint pupils)**, and hypotension, which are contrary to the patient's symptoms. - Patients typically exhibit central nervous system **depression**, rather than the hyperactive state seen here. *Morphine* - Similar to heroin, morphine is an **opioid** and causes symptoms like **respiratory depression, bradycardia, miosis**, and hypotension. - These effects are the opposite of the **sympathomimetic** signs observed in the patient. *Chlorpheniramine* - Chlorpheniramine is an **antihistamine** with significant **anticholinergic effects**. An overdose might cause **mydriasis and tachycardia**, but not typically severe hypertension or hyperthermia as the primary features. - Other anticholinergic signs such as **dry mucous membranes, urinary retention, and altered mental status (delirium)** would also be expected. *Organophosphate* - Organophosphate poisoning causes a **cholinergic toxidrome** due to **acetylcholinesterase inhibition**, resulting in excessive cholinergic stimulation. - Classic presentation includes **SLUDGE syndrome** (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis) along with **miosis (pinpoint pupils), bradycardia, bronchospasm**, and muscle fasciculations. - These findings are the **opposite** of the sympathomimetic signs seen in this patient.

Q: A 45-year-old patient with a history of depression was initially being treated with sertraline, but his symptoms were not adequately controlled. His medication regimen was changed to include an MAO inhibitor and amitriptyline. Shortly after the change in medication, the patient developed agitation, seizures, hyperreflexia, and tremor. Which of the following is the most appropriate treatment for this patient?

Cyproheptadine. ***Cyproheptadine*** - This patient exhibits symptoms of **serotonin syndrome** (agitation, seizures, hyperreflexia, tremor) due to the combination of an **MAO inhibitor** and **amitriptyline**. - **Cyproheptadine** is a **serotonin antagonist** and is the most appropriate treatment for reversing the effects of serotonin syndrome. - Treatment also includes discontinuing offending agents and supportive care. *Lorazepam* - **Lorazepam** is a **benzodiazepine** that can help manage agitation and seizures, but it does not address the underlying serotonin overstimulation. - It would be used as an adjunct for symptom control, not as the primary treatment for serotonin syndrome. *Dantrolene* - **Dantrolene** is a **muscle relaxant** used for **neuroleptic malignant syndrome (NMS)** and **malignant hyperthermia**. - While NMS and serotonin syndrome can have overlapping features (hyperthermia, rigidity), dantrolene is not indicated for serotonin syndrome. - Cyproheptadine is the specific serotonin antagonist needed for this condition. *L-carnitine* - **L-carnitine** is a supplement often used for conditions like **carnitine deficiency** or certain **metabolic disorders**. - It has no role in the treatment of serotonin syndrome. *Leucovorin* - **Leucovorin** (folinic acid) is used to **rescue bone marrow** from the toxic effects of **methotrexate** or to enhance the effects of **fluorouracil**. - It is not indicated for the treatment of serotonin syndrome.

Q: Why is atropine mixed with diphenoxylate in combination medications?

To prevent abuse of diphenoxylate. ***To prevent abuse of diphenoxylate*** - **Diphenoxylate** is an opioid derivative with potential for abuse due to its CNS effects at high doses. - Adding **atropine** discourages abuse by producing unpleasant anticholinergic side effects (e.g., dry mouth, blurred vision, urinary retention) if high doses are ingested. *Atropine decreases the adverse effects of diphenoxylate* - **Atropine** does not decrease the adverse effects of diphenoxylate; rather, it introduces its own set of **anticholinergic** side effects. - The combination is designed to make recreational use unpleasant, not to mitigate side effects of diphenoxylate itself. *To enhance the antidiarrheal effect* - While atropine has some anticholinergic properties that can reduce gut motility, its primary purpose in this combination is **not to enhance the antidiarrheal effect**. - **Diphenoxylate** is the primary antidiarrheal agent, and the amount of atropine included is typically subtherapeutic for significant antidiarrheal action. *Atropine produces direct spasmolytic action* - Although **atropine** does have **spasmolytic** effects by blocking muscarinic receptors in the gut, this is not the main reason for its addition to diphenoxylate. - The dosage of atropine in the combination is usually low enough to cause unpleasant systemic effects but not necessarily to significantly contribute to the antispasmodic action at therapeutic doses of diphenoxylate. *Atropine increases the bioavailability of diphenoxylate* - **Atropine** does not affect the **pharmacokinetics** or **bioavailability** of diphenoxylate. - The two drugs are combined for abuse deterrence purposes, not for any pharmacokinetic interaction or enhancement of drug absorption.

Q: Which of the following is the most appropriate treatment for an overactive bladder in a patient with dementia?

Tolterodine. ***Tolterodine*** - **Tolterodine** is a **muscarinic antagonist** that blocks acetylcholine receptors in the bladder, reducing detrusor muscle contractions and overactive bladder symptoms. - Unlike some other anticholinergics like oxybutynin, it has a **lower propensity to cross the blood-brain barrier** and thus a reduced risk of exacerbating cognitive impairment in patients with dementia. *Mirabegron* - **Mirabegron** is a **beta-3 adrenergic agonist** that relaxes the detrusor muscle, increasing bladder capacity. - While it has a different mechanism of action and is less likely to cause anticholinergic cognitive side effects than older anticholinergics, it can still cause **hypertension** and **tachycardia**, which may be problematic in elderly patients with comorbidities. *Behavioral therapy/bladder training* - **Behavioral therapy** and **bladder training** are important first-line treatments for overactive bladder. - However, for patients with **dementia**, cognitive impairment often makes adherence to and understanding of these complex therapies challenging or impossible without significant caregiver support. *Oxybutynin* - **Oxybutynin** is an **anticholinergic drug** that is effective for overactive bladder. - However, it has a **high affinity for muscarinic receptors** in the brain and readily crosses the blood-brain barrier, significantly increasing the risk of **cognitive impairment, confusion, and delirium** in elderly patients, especially those with pre-existing dementia. *Trospium* - **Trospium** is a **quaternary amine anticholinergic** that is hydrophilic and has minimal blood-brain barrier penetration. - While theoretically safer than oxybutynin in terms of CNS effects, it has **lower bladder selectivity** compared to tolterodine and may cause more peripheral anticholinergic side effects (dry mouth, constipation).

Q: Caffeine impairs sleep by which of the following mechanisms?

Blocks adenosine action and promotes wakefulness. ***Blocks adenosine action and promotes wakefulness*** - Caffeine functions as a competitive **adenosine receptor antagonist**, primarily at A1 and A2A receptors in the brain. - By blocking adenosine, which is an endogenous sleep-promoting neurochemical, caffeine reduces its inhibitory effects on wakefulness centers, thus **promoting alertness** and delaying sleep onset. *Activates locus coeruleus & promotes wakefulness* - While caffeine indirectly influences brain regions that promote wakefulness, its primary mechanism is not direct activation of the **locus coeruleus**. - Its effects on wakefulness are mediated more broadly through antagonism of **adenosine receptors.** *No role in maintaining wakefulness* - This statement is incorrect; caffeine is well-known for its **psychoactive properties** and its ability to increase alertness and reduce fatigue. - Its widespread consumption is largely attributed to its role in **promoting wakefulness** and improving cognitive function. *Activates histamine release and prevents sleep* - Caffeine does not significantly activate **histamine release** as a primary mechanism for its wake-promoting effects. - The wake-promoting effects of histamine are mediated via H1 receptors, but this is a separate pathway not directly targeted by caffeine. *Inhibits phosphodiesterase and increases cAMP levels* - While caffeine does inhibit **phosphodiesterase enzymes** (particularly at higher concentrations), this is not the primary mechanism for its wake-promoting effects. - The concentrations required for significant phosphodiesterase inhibition are much higher than those achieved with typical caffeine consumption; **adenosine receptor antagonism** occurs at much lower doses and is the dominant mechanism for its effects on sleep and alertness.

Q: A Myasthenia Gravis patient on mycophenolate and pyridostigmine presents with hypercalcemia. Apart from the obvious drug-related cause, what other condition could be associated with hypercalcemia in this patient?

Non-Small Cell Lung Cancer (NSCLC). ***Non-Small Cell Lung Cancer (NSCLC)*** - **Hypercalcemia of malignancy** is a common paraneoplastic syndrome in NSCLC, particularly squamous cell carcinoma, due to the production of **parathyroid hormone-related protein (PTHrP)**. - Patients with myasthenia gravis, especially those with thymoma, have an increased risk of developing other malignancies, including lung cancer, making this an important consideration. *Drug induced* - While certain medications can cause hypercalcemia, the question specifically asks for a condition **apart from the obvious drug-related cause**. - Medications like **thiazide diuretics**, **lithium**, or excessive **vitamin D** supplementation are known causes of hypercalcemia. *Parathyroid adenoma* - A parathyroid adenoma causes **primary hyperparathyroidism**, characterized by elevated PTH and hypercalcemia. - While possible, the association with myasthenia gravis and the increased risk of malignancy make **paraneoplastic syndrome** a more contextual answer here given the prompt. *Small Cell Lung Cancer (SCLC)* - SCLC is more commonly associated with other paraneoplastic syndromes like **SIADH (syndrome of inappropriate antidiuretic hormone secretion)** due to ectopic ADH production, or **Cushing's syndrome** due to ectopic ACTH production. - While hypercalcemia can rarely occur, it is **less common** and typically not due to PTHrP in SCLC compared to NSCLC. *Sarcoidosis* - Sarcoidosis can cause hypercalcemia through increased production of **1,25-dihydroxyvitamin D** by activated macrophages in granulomas, leading to enhanced intestinal calcium absorption. - However, in the context of a myasthenia gravis patient with the clinical scenario described, **malignancy-associated hypercalcemia** (particularly NSCLC) is a more likely and clinically relevant consideration.

Q: A patient has a history of vomiting and was given an antiemetic. The patient subsequently developed abnormal movements (likely extrapyramidal symptoms or dystonia). What medication should be given to manage these abnormal movements?

Benzhexol. ***Benzhexol*** - **Extrapyramidal symptoms (EPS)** and **dystonia** are often caused by dopamine receptor blockade, and **anticholinergic medications** like benzhexol help restore the **dopamine-acetylcholine balance**. - Benzhexol is a **muscarinic antagonist** that effectively reduces drug-induced Parkinsonism, dystonia, and akathisia by acting centrally. - It is the **preferred oral agent** for ongoing management of drug-induced movement disorders. *Diphenhydramine* - Diphenhydramine is an **antihistamine** with **anticholinergic properties** that can be used for **acute dystonic reactions**, particularly when given parenterally (IV/IM). - While effective for acute management, benzhexol is generally preferred for **ongoing oral therapy** and has more potent central anticholinergic effects. *Hyoscine* - While hyoscine is also an **anticholinergic agent**, it is primarily used for preventing **motion sickness** and managing **postoperative nausea and vomiting**. - Its efficacy in reversing acute extrapyramidal symptoms induced by neuroleptics or antiemetics is generally **less pronounced** compared to agents like benzhexol. *Methyl dopa* - Methyl dopa is an **alpha-2 adrenergic agonist** primarily used in the treatment of **hypertension**, especially in pregnancy. - It works by reducing sympathetic outflow and is **not indicated** for managing extrapyramidal symptoms or dystonia. *Cyproheptadine* - Cyproheptadine is an **antihistamine** with **serotonin antagonist** properties, used to treat allergic reactions, appetite stimulation, and occasionally **serotonin syndrome**. - It does not have significant anticholinergic effects that would alleviate medication-induced extrapyramidal symptoms or dystonia.

A 30-year-old drug addict presents to the emergency department with signs of unknown drug poisoning. The patient exhibits dilated pupils, diaphoresis, tachycardia, and tremors. On examination, the blood pressure is 180/110 mmHg, and the heart rate is 120 beats per minute. What is the most likely diagnosis?

A 45-year-old patient with a history of depression was initially being treated with sertraline, but his symptoms were not adequately controlled. His medication regimen was changed to include an MAO inhibitor and amitriptyline. Shortly after the change in medication, the patient developed agitation, seizures, hyperreflexia, and tremor. Which of the following is the most appropriate treatment for this patient?

Which of the following is a selective norepinephrine reuptake inhibitor that can be used for the treatment of ADHD?

Why is atropine mixed with diphenoxylate in combination medications?

Which of the following is the most appropriate treatment for an overactive bladder in a patient with dementia?

Caffeine impairs sleep by which of the following mechanisms?

A Myasthenia Gravis patient on mycophenolate and pyridostigmine presents with hypercalcemia. Apart from the obvious drug-related cause, what other condition could be associated with hypercalcemia in this patient?

Q10

A patient has a history of vomiting and was given an antiemetic. The patient subsequently developed abnormal movements (likely extrapyramidal symptoms or dystonia). What medication should be given to manage these abnormal movements?

Cholinergic/Adrenergic drugs US Medical PG Practice Questions and MCQs

Question 1: A chronic smoker wants to quit smoking. Which of the following is the MOST appropriate first-line pharmacotherapy for smoking cessation?

A. Mirtazapine
B. Varenicline (Correct Answer)
C. Bupropion
D. Nicotine replacement therapy
E. Clonidine

Explanation: ***Varenicline*** - **Varenicline** is a **partial agonist** at the **α4β2 nicotinic acetylcholine receptor**, the primary receptor involved in nicotine addiction. - It reduces cravings and withdrawal symptoms while blocking the reinforcing effects of nicotine from cigarettes. - Studies show **varenicline has the highest efficacy** among pharmacological agents for smoking cessation, with superior quit rates compared to bupropion and NRT. - **First-line agent** recommended by clinical guidelines for smoking cessation. *Mirtazapine* - Mirtazapine is a **tetracyclic antidepressant** (α2-antagonist, 5-HT2 and 5-HT3 antagonist) used for **major depressive disorder**. - **Not indicated** for smoking cessation and lacks evidence for efficacy in this context. - May cause weight gain and sedation, which are not beneficial for smoking cessation. *Bupropion* - **Bupropion** is an **atypical antidepressant** and **norepinephrine-dopamine reuptake inhibitor (NDRI)** that also antagonizes nicotinic receptors. - Effective **first-line agent** for smoking cessation, reducing cravings and withdrawal symptoms. - However, studies show **lower efficacy compared to varenicline** in head-to-head trials. - Contraindicated in patients with seizure disorders or eating disorders. *Nicotine replacement therapy* - **NRT** (patches, gum, lozenges, inhalers, nasal spray) provides controlled nicotine delivery without harmful tobacco combustion products. - Effective **first-line therapy** that reduces withdrawal symptoms and cravings. - Generally **less effective than varenicline** when used alone, but can be combined with other therapies. - Safest option with minimal contraindications. *Clonidine* - **Clonidine** is a **central α2-agonist** primarily used for hypertension. - Considered a **second-line agent** for smoking cessation, used only when first-line therapies fail or are contraindicated. - Less effective than first-line agents and associated with more adverse effects (sedation, dry mouth, hypotension). - Not routinely recommended for smoking cessation.

Question 2: A mother reports that her daughter ingested a substance in an unknown dose. The girl presents with hypertension, tachycardia, mydriasis, and hyperthermia. What is the most likely substance?

A. Heroin
B. Morphine
C. Cocaine (Correct Answer)
D. Chlorpheniramine
E. Organophosphate

Explanation: ***Cocaine*** - The presented symptoms of **hypertension, tachycardia, mydriasis, and hyperthermia** are characteristic of a **sympathomimetic toxidrome**, frequently caused by cocaine overdose. - Cocaine acts as a **norepinephrine-dopamine-serotonin reuptake inhibitor**, leading to excessive stimulation of the central and peripheral nervous systems. *Heroin* - Heroin is an **opioid**, and overdose generally presents with **respiratory depression, bradycardia, miosis (pinpoint pupils)**, and hypotension, which are contrary to the patient's symptoms. - Patients typically exhibit central nervous system **depression**, rather than the hyperactive state seen here. *Morphine* - Similar to heroin, morphine is an **opioid** and causes symptoms like **respiratory depression, bradycardia, miosis**, and hypotension. - These effects are the opposite of the **sympathomimetic** signs observed in the patient. *Chlorpheniramine* - Chlorpheniramine is an **antihistamine** with significant **anticholinergic effects**. An overdose might cause **mydriasis and tachycardia**, but not typically severe hypertension or hyperthermia as the primary features. - Other anticholinergic signs such as **dry mucous membranes, urinary retention, and altered mental status (delirium)** would also be expected. *Organophosphate* - Organophosphate poisoning causes a **cholinergic toxidrome** due to **acetylcholinesterase inhibition**, resulting in excessive cholinergic stimulation. - Classic presentation includes **SLUDGE syndrome** (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis) along with **miosis (pinpoint pupils), bradycardia, bronchospasm**, and muscle fasciculations. - These findings are the **opposite** of the sympathomimetic signs seen in this patient.

Question 3: A 30-year-old drug addict presents to the emergency department with signs of unknown drug poisoning. The patient exhibits dilated pupils, diaphoresis, tachycardia, and tremors. On examination, the blood pressure is 180/110 mmHg, and the heart rate is 120 beats per minute. What is the most likely diagnosis?

A. Cocaine intoxication (Correct Answer)
B. Dhatura poisoning
C. Cannabis poisoning
D. Alcohol intoxication
E. Amphetamine intoxication

Explanation: ***Cocaine intoxication*** - Cocaine is a potent **sympathomimetic** drug that leads to a hyperadrenergic state, causing symptoms like **dilated pupils**, diaphoresis, tachycardia, and hypertension. - The patient's presentation with significant **tachycardia (120 bpm)** and **hypertension (180/110 mmHg)**, along with a history of drug abuse, strongly points towards cocaine. - Cocaine has a **shorter duration of action** (30-90 minutes) compared to amphetamines, but the clinical presentation is nearly identical. *Amphetamine intoxication* - **Amphetamines** also cause a sympathomimetic toxidrome very similar to cocaine, with mydriasis, diaphoresis, tachycardia, and hypertension. - However, the acute presentation is clinically indistinguishable from cocaine, though amphetamines typically have a **longer duration of action** (4-8 hours). - Both diagnoses would be managed similarly in the acute setting. *Dhatura poisoning* - **Dhatura** causes an **anticholinergic toxidrome**, characterized by symptoms such as "hot, dry, blind, red, and mad." - Key features of dhatura poisoning include **dry mucous membranes**, dilated pupils (mydriasis), flushed skin, but typically a **normal or elevated temperature** rather than diaphoresis and less pronounced hypertension. *Cannabis poisoning* - **Cannabis intoxication** typically leads to symptoms like **conjunctival injection**, dry mouth, increased appetite, and impaired coordination. - While it can cause mild tachycardia, it generally does not result in the severe **hypertension**, profound diaphoresis, or significant tremors seen in this patient. *Alcohol intoxication* - **Alcohol intoxication** usually presents with central nervous system depression, such as **slurred speech**, ataxia, nystagmus, and drowsiness. - While alcohol can affect blood pressure and heart rate, it typically causes **hypotension** or mild hypertension, and it does not produce the marked sympathomimetic effects such as **mydriasis** and profound diaphoresis observed here.

Question 4: A 45-year-old patient with a history of depression was initially being treated with sertraline, but his symptoms were not adequately controlled. His medication regimen was changed to include an MAO inhibitor and amitriptyline. Shortly after the change in medication, the patient developed agitation, seizures, hyperreflexia, and tremor. Which of the following is the most appropriate treatment for this patient?

A. Cyproheptadine (Correct Answer)
B. Lorazepam
C. L-carnitine
D. Leucovorin
E. Dantrolene

Explanation: ***Cyproheptadine*** - This patient exhibits symptoms of **serotonin syndrome** (agitation, seizures, hyperreflexia, tremor) due to the combination of an **MAO inhibitor** and **amitriptyline**. - **Cyproheptadine** is a **serotonin antagonist** and is the most appropriate treatment for reversing the effects of serotonin syndrome. - Treatment also includes discontinuing offending agents and supportive care. *Lorazepam* - **Lorazepam** is a **benzodiazepine** that can help manage agitation and seizures, but it does not address the underlying serotonin overstimulation. - It would be used as an adjunct for symptom control, not as the primary treatment for serotonin syndrome. *Dantrolene* - **Dantrolene** is a **muscle relaxant** used for **neuroleptic malignant syndrome (NMS)** and **malignant hyperthermia**. - While NMS and serotonin syndrome can have overlapping features (hyperthermia, rigidity), dantrolene is not indicated for serotonin syndrome. - Cyproheptadine is the specific serotonin antagonist needed for this condition. *L-carnitine* - **L-carnitine** is a supplement often used for conditions like **carnitine deficiency** or certain **metabolic disorders**. - It has no role in the treatment of serotonin syndrome. *Leucovorin* - **Leucovorin** (folinic acid) is used to **rescue bone marrow** from the toxic effects of **methotrexate** or to enhance the effects of **fluorouracil**. - It is not indicated for the treatment of serotonin syndrome.

Question 5: Which of the following is a selective norepinephrine reuptake inhibitor that can be used for the treatment of ADHD?

A. Reboxetine
B. Methylphenidate
C. Guanfacine
D. Modafinil
E. Atomoxetine (Correct Answer)

Explanation: ***Atomoxetine*** - **Atomoxetine** is a **selective norepinephrine reuptake inhibitor (SNRI)** that is **FDA-approved specifically for the treatment of ADHD** in children, adolescents, and adults. - It works by **selectively blocking the presynaptic norepinephrine transporter**, increasing norepinephrine availability in the prefrontal cortex and other brain regions involved in attention and impulse control. - Unlike stimulant medications, atomoxetine is **not a controlled substance** and is considered a first-line **non-stimulant option** for ADHD treatment. - It is particularly useful in patients with comorbid anxiety, tic disorders, or substance abuse concerns. *Reboxetine* - While **reboxetine** is technically a **selective norepinephrine reuptake inhibitor**, it is primarily used as an **antidepressant** and is **not approved for ADHD treatment**. - It has been investigated off-label for ADHD, but it is not a standard or recommended treatment option. - Reboxetine has **limited global availability** and has been withdrawn from many markets due to efficacy concerns. *Methylphenidate* - **Methylphenidate** is a **stimulant** medication that inhibits the reuptake of both **dopamine and norepinephrine**, making it **non-selective**. - It is a first-line treatment for ADHD, but its mechanism of action involves dual monoamine reuptake inhibition, not selective norepinephrine reuptake. *Guanfacine* - **Guanfacine** is an **alpha-2 adrenergic agonist**, not a norepinephrine reuptake inhibitor. - It works by stimulating postsynaptic alpha-2A receptors in the prefrontal cortex, which enhances prefrontal cortex function and improves attention and impulse control. *Modafinil* - **Modafinil** is a wakefulness-promoting agent with a **complex, non-selective mechanism** involving dopamine, norepinephrine, histamine, and orexin systems. - It is primarily used for **narcolepsy** and excessive daytime sleepiness, not as a primary ADHD treatment. - It is **not classified as a selective norepinephrine reuptake inhibitor**.

Question 6: Why is atropine mixed with diphenoxylate in combination medications?

A. Atropine decreases the adverse effects of diphenoxylate
B. To prevent abuse of diphenoxylate (Correct Answer)
C. To enhance the antidiarrheal effect
D. Atropine produces direct spasmolytic action
E. Atropine increases the bioavailability of diphenoxylate

Explanation: ***To prevent abuse of diphenoxylate*** - **Diphenoxylate** is an opioid derivative with potential for abuse due to its CNS effects at high doses. - Adding **atropine** discourages abuse by producing unpleasant anticholinergic side effects (e.g., dry mouth, blurred vision, urinary retention) if high doses are ingested. *Atropine decreases the adverse effects of diphenoxylate* - **Atropine** does not decrease the adverse effects of diphenoxylate; rather, it introduces its own set of **anticholinergic** side effects. - The combination is designed to make recreational use unpleasant, not to mitigate side effects of diphenoxylate itself. *To enhance the antidiarrheal effect* - While atropine has some anticholinergic properties that can reduce gut motility, its primary purpose in this combination is **not to enhance the antidiarrheal effect**. - **Diphenoxylate** is the primary antidiarrheal agent, and the amount of atropine included is typically subtherapeutic for significant antidiarrheal action. *Atropine produces direct spasmolytic action* - Although **atropine** does have **spasmolytic** effects by blocking muscarinic receptors in the gut, this is not the main reason for its addition to diphenoxylate. - The dosage of atropine in the combination is usually low enough to cause unpleasant systemic effects but not necessarily to significantly contribute to the antispasmodic action at therapeutic doses of diphenoxylate. *Atropine increases the bioavailability of diphenoxylate* - **Atropine** does not affect the **pharmacokinetics** or **bioavailability** of diphenoxylate. - The two drugs are combined for abuse deterrence purposes, not for any pharmacokinetic interaction or enhancement of drug absorption.

Question 7: Which of the following is the most appropriate treatment for an overactive bladder in a patient with dementia?

A. Tolterodine (Correct Answer)
B. Mirabegron
C. Behavioral therapy/bladder training
D. Oxybutynin
E. Trospium

Explanation: ***Tolterodine*** - **Tolterodine** is a **muscarinic antagonist** that blocks acetylcholine receptors in the bladder, reducing detrusor muscle contractions and overactive bladder symptoms. - Unlike some other anticholinergics like oxybutynin, it has a **lower propensity to cross the blood-brain barrier** and thus a reduced risk of exacerbating cognitive impairment in patients with dementia. *Mirabegron* - **Mirabegron** is a **beta-3 adrenergic agonist** that relaxes the detrusor muscle, increasing bladder capacity. - While it has a different mechanism of action and is less likely to cause anticholinergic cognitive side effects than older anticholinergics, it can still cause **hypertension** and **tachycardia**, which may be problematic in elderly patients with comorbidities. *Behavioral therapy/bladder training* - **Behavioral therapy** and **bladder training** are important first-line treatments for overactive bladder. - However, for patients with **dementia**, cognitive impairment often makes adherence to and understanding of these complex therapies challenging or impossible without significant caregiver support. *Oxybutynin* - **Oxybutynin** is an **anticholinergic drug** that is effective for overactive bladder. - However, it has a **high affinity for muscarinic receptors** in the brain and readily crosses the blood-brain barrier, significantly increasing the risk of **cognitive impairment, confusion, and delirium** in elderly patients, especially those with pre-existing dementia. *Trospium* - **Trospium** is a **quaternary amine anticholinergic** that is hydrophilic and has minimal blood-brain barrier penetration. - While theoretically safer than oxybutynin in terms of CNS effects, it has **lower bladder selectivity** compared to tolterodine and may cause more peripheral anticholinergic side effects (dry mouth, constipation).

Question 8: Caffeine impairs sleep by which of the following mechanisms?

A. Blocks adenosine action and promotes wakefulness (Correct Answer)
B. Activates locus coeruleus & promotes wakefulness
C. No role in maintaining wakefulness
D. Activates histamine release and prevents sleep
E. Inhibits phosphodiesterase and increases cAMP levels

Explanation: ***Blocks adenosine action and promotes wakefulness*** - Caffeine functions as a competitive **adenosine receptor antagonist**, primarily at A1 and A2A receptors in the brain. - By blocking adenosine, which is an endogenous sleep-promoting neurochemical, caffeine reduces its inhibitory effects on wakefulness centers, thus **promoting alertness** and delaying sleep onset. *Activates locus coeruleus & promotes wakefulness* - While caffeine indirectly influences brain regions that promote wakefulness, its primary mechanism is not direct activation of the **locus coeruleus**. - Its effects on wakefulness are mediated more broadly through antagonism of **adenosine receptors.** *No role in maintaining wakefulness* - This statement is incorrect; caffeine is well-known for its **psychoactive properties** and its ability to increase alertness and reduce fatigue. - Its widespread consumption is largely attributed to its role in **promoting wakefulness** and improving cognitive function. *Activates histamine release and prevents sleep* - Caffeine does not significantly activate **histamine release** as a primary mechanism for its wake-promoting effects. - The wake-promoting effects of histamine are mediated via H1 receptors, but this is a separate pathway not directly targeted by caffeine. *Inhibits phosphodiesterase and increases cAMP levels* - While caffeine does inhibit **phosphodiesterase enzymes** (particularly at higher concentrations), this is not the primary mechanism for its wake-promoting effects. - The concentrations required for significant phosphodiesterase inhibition are much higher than those achieved with typical caffeine consumption; **adenosine receptor antagonism** occurs at much lower doses and is the dominant mechanism for its effects on sleep and alertness.

Question 9: A Myasthenia Gravis patient on mycophenolate and pyridostigmine presents with hypercalcemia. Apart from the obvious drug-related cause, what other condition could be associated with hypercalcemia in this patient?

A. Drug induced
B. Parathyroid adenoma
C. Small Cell Lung Cancer (SCLC)
D. Non-Small Cell Lung Cancer (NSCLC) (Correct Answer)
E. Sarcoidosis

Explanation: ***Non-Small Cell Lung Cancer (NSCLC)*** - **Hypercalcemia of malignancy** is a common paraneoplastic syndrome in NSCLC, particularly squamous cell carcinoma, due to the production of **parathyroid hormone-related protein (PTHrP)**. - Patients with myasthenia gravis, especially those with thymoma, have an increased risk of developing other malignancies, including lung cancer, making this an important consideration. *Drug induced* - While certain medications can cause hypercalcemia, the question specifically asks for a condition **apart from the obvious drug-related cause**. - Medications like **thiazide diuretics**, **lithium**, or excessive **vitamin D** supplementation are known causes of hypercalcemia. *Parathyroid adenoma* - A parathyroid adenoma causes **primary hyperparathyroidism**, characterized by elevated PTH and hypercalcemia. - While possible, the association with myasthenia gravis and the increased risk of malignancy make **paraneoplastic syndrome** a more contextual answer here given the prompt. *Small Cell Lung Cancer (SCLC)* - SCLC is more commonly associated with other paraneoplastic syndromes like **SIADH (syndrome of inappropriate antidiuretic hormone secretion)** due to ectopic ADH production, or **Cushing's syndrome** due to ectopic ACTH production. - While hypercalcemia can rarely occur, it is **less common** and typically not due to PTHrP in SCLC compared to NSCLC. *Sarcoidosis* - Sarcoidosis can cause hypercalcemia through increased production of **1,25-dihydroxyvitamin D** by activated macrophages in granulomas, leading to enhanced intestinal calcium absorption. - However, in the context of a myasthenia gravis patient with the clinical scenario described, **malignancy-associated hypercalcemia** (particularly NSCLC) is a more likely and clinically relevant consideration.

Question 10: A patient has a history of vomiting and was given an antiemetic. The patient subsequently developed abnormal movements (likely extrapyramidal symptoms or dystonia). What medication should be given to manage these abnormal movements?

A. Hyoscine
B. Methyl dopa
C. Benzhexol (Correct Answer)
D. Cyproheptadine
E. Diphenhydramine

Explanation: ***Benzhexol*** - **Extrapyramidal symptoms (EPS)** and **dystonia** are often caused by dopamine receptor blockade, and **anticholinergic medications** like benzhexol help restore the **dopamine-acetylcholine balance**. - Benzhexol is a **muscarinic antagonist** that effectively reduces drug-induced Parkinsonism, dystonia, and akathisia by acting centrally. - It is the **preferred oral agent** for ongoing management of drug-induced movement disorders. *Diphenhydramine* - Diphenhydramine is an **antihistamine** with **anticholinergic properties** that can be used for **acute dystonic reactions**, particularly when given parenterally (IV/IM). - While effective for acute management, benzhexol is generally preferred for **ongoing oral therapy** and has more potent central anticholinergic effects. *Hyoscine* - While hyoscine is also an **anticholinergic agent**, it is primarily used for preventing **motion sickness** and managing **postoperative nausea and vomiting**. - Its efficacy in reversing acute extrapyramidal symptoms induced by neuroleptics or antiemetics is generally **less pronounced** compared to agents like benzhexol. *Methyl dopa* - Methyl dopa is an **alpha-2 adrenergic agonist** primarily used in the treatment of **hypertension**, especially in pregnancy. - It works by reducing sympathetic outflow and is **not indicated** for managing extrapyramidal symptoms or dystonia. *Cyproheptadine* - Cyproheptadine is an **antihistamine** with **serotonin antagonist** properties, used to treat allergic reactions, appetite stimulation, and occasionally **serotonin syndrome**. - It does not have significant anticholinergic effects that would alleviate medication-induced extrapyramidal symptoms or dystonia.

Question 11: A 30-year-old male presents with a history of consuming an unknown substance. On examination, the patient has diaphoresis, headache, and features resembling acute coronary spasm. Which of the following clinical features is least likely to be present in this patient?

A. Hypertension
B. Tachycardia
C. Hyperthermia
D. Bradycardia (Correct Answer)
E. Mydriasis

Explanation: ***Bradycardia*** - The presented symptoms of diaphoresis, headache, and coronary spasm are consistent with **stimulant intoxication** (e.g., cocaine, amphetamines). - Stimulants typically cause **tachycardia** due to sympathetic overactivity, making bradycardia the least likely finding. *Hypertension* - **Stimulant intoxication** leads to increased sympathetic activity, causing **vasoconstriction** and elevated blood pressure. - This is a common and expected finding in cases presenting with coronary spasm due to substance abuse. *Tachycardia* - **Sympathetic overstimulation** from an unknown substance, particularly stimulants, directly increases heart rate. - This symptom closely aligns with the patient's presentation of diaphoresis and coronary spasm. *Hyperthermia* - Elevated body temperature is a frequent consequence of **stimulant overdose** due to increased metabolic activity and impaired thermoregulation. - **Diaphoresis** (sweating) can be a compensatory mechanism for hyperthermia or a direct effect of sympathetic activation. *Mydriasis* - **Pupillary dilation** is a characteristic finding in sympathomimetic toxidrome caused by stimulant drugs. - This occurs due to alpha-adrenergic stimulation of the radial muscle of the iris and is commonly seen with cocaine or amphetamine use.

Question 12: A child accidentally ingested a fruit from a tree while playing. After the ingestion, he presented with symptoms of restlessness, painful swallowing, photophobia, dry skin, urinary retention, and elevated body temperature. What is the most likely cause of poisoning, and what is the appropriate antidote for it?

A. Datura poisoning & Physostigmine (Correct Answer)
B. Yellow Oleander poisoning & Atropine
C. Datura poisoning & Pralidoxime
D. Organophosphate poisoning & Pralidoxime
E. Mushroom (Amanita) poisoning & Atropine

Explanation: ***Datura poisoning & Physostigmine*** - The symptoms of **restlessness, painful swallowing, photophobia, dry skin, urinary retention, and elevated body temperature** are classic signs of **anticholinergic toxicity**, which is characteristic of **Datura poisoning**. - **Physostigmine** is an **acetylcholinesterase inhibitor** that increases acetylcholine levels, effectively reversing the anticholinergic effects of Datura. *Yellow Oleander poisoning & Atropine* - **Yellow Oleander poisoning** primarily causes **cardiac effects** (e.g., bradycardia, arrhythmias) due to cardiac glycosides, not the anticholinergic symptoms described. - **Atropine** is an **anticholinergic agent** and would worsen the symptoms of Datura poisoning rather than being an antidote for it. *Datura poisoning & Pralidoxime* - While **Datura poisoning** is correct given the symptoms, **Pralidoxime** is an antidote for **organophosphate poisoning**, acting as a cholinesterase reactivator, and has no efficacy in anticholinergic toxicity. *Organophosphate poisoning & Pralidoxime* - **Organophosphate poisoning** presents with **cholinergic symptoms** (e.g., salivation, lacrimation, urination, defecation, GI upset, emesis, miosis, bronchospasm, bradycardia), which are opposite to the anticholinergic signs seen here. - Although **Pralidoxime** is a correct antidote for organophosphate poisoning, the clinical picture does not support this diagnosis. *Mushroom (Amanita) poisoning & Atropine* - **Certain mushroom poisonings** (e.g., muscarine-containing mushrooms like *Inocybe* and *Clitocybe* species) cause **cholinergic symptoms** (salivation, sweating, miosis, bradycardia), not anticholinergic symptoms. - While **Atropine** would be the correct antidote for muscarinic mushroom poisoning, the clinical presentation here shows anticholinergic toxicity, not cholinergic excess.

Question 13: Beta 2 receptors act via which of the following secondary messenger systems

A. Adenylate Cyclase (Correct Answer)
B. Phospholipase C
C. Guanylate Cyclase
D. Direct ion channel activation
E. Tyrosine Kinase

Explanation: ***Adenylate Cyclase*** - **Beta-2 adrenergic receptors** are G-protein coupled receptors that primarily activate the **Gs protein**. - Activation of Gs protein leads to the stimulation of **adenylate cyclase**, which converts ATP to **cAMP**, a crucial secondary messenger for various cellular responses. *Phospholipase C* - **Phospholipase C** is typically activated by **Gq protein-coupled receptors**, such as alpha-1 adrenergic receptors or M1/M3 muscarinic receptors. - Its activation leads to the production of **IP3** and **DAG**, which then trigger intracellular calcium release and protein kinase C activation, respectively. *Guanylate Cyclase* - **Guanylate cyclase** produces **cGMP** as a secondary messenger and is primarily associated with **nitric oxide signaling** (soluble guanylate cyclase) or **natriuretic peptide receptors** (particulate guanylate cyclase). - This system is distinct from the adrenergic receptor pathways. *Direct ion channel activation* - **Direct ion channel activation** occurs in **ligand-gated ion channels**, where the binding of a neurotransmitter directly opens an ion pore without the involvement of G-proteins or secondary messengers. - Examples include nicotinic acetylcholine receptors and GABA-A receptors, which are functionally different from the G-protein coupled **beta-2 receptors**. *Tyrosine Kinase* - **Tyrosine kinase** signaling is characteristic of **receptor tyrosine kinases (RTKs)**, such as insulin receptors and growth factor receptors (e.g., EGF, PDGF receptors). - These receptors undergo autophosphorylation and initiate signaling cascades independent of G-proteins, making them distinct from **beta-2 adrenergic receptors**.

Question 14: A 68-year-old woman is brought to the emergency department by her son for altered mental status. She recently had a right knee arthroplasty and was discharged 2 days ago. Her medical history is significant for type 2 diabetes mellitus and hypertension, for which she takes metformin and hydrochlorothiazide, respectively. She also had left cataract surgery 1 year ago. Her temperature is 97°F (36.1°C), blood pressure is 99/70 mmHg, pulse is 60/min, respirations are 8/min. Her exam is notable for anisocoria with an irregularly shaped left pupil and a 1 mm in diameter right pupil. She opens her eyes and withdraws all of her limbs to loud voice and painful stimulation. Her fingerstick glucose level is 79. The patient does not have any intravenous access at this time. What is the best next step in management?

A. Forced air warmer
B. Intubate
C. Computed tomography of head without contrast
D. Orange juice by mouth
E. Intranasal naloxone (Correct Answer)

Explanation: ***Intranasal naloxone*** - The patient's **depressed respiratory rate (8/min)**, **bradycardia (60/min)**, **hypotension (99/70 mmHg)**, and **altered mental status** following recent surgery (where opioids are commonly prescribed for pain) strongly suggest **opioid overdose**. - **Naloxone** is a rapidly acting opioid antagonist that can reverse these effects, and the intranasal route is appropriate given the lack of intravenous access. *Forced air warmer* - While the patient is **hypothermic (97°F/36.1°C)**, warming alone will not address the primary cause of her respiratory depression and altered mental status. - Addressing the underlying opioid overdose is more critical for immediate stabilization than temperature correction. *Intubate* - Although the patient has **respiratory depression**, intubation is an invasive procedure that should be considered after less invasive measures like naloxone administration, especially if the respiratory drive does not improve. - The patient is still withdrawing to pain, indicating some level of neurologic response, and her oxygen saturation is not given, so direct intubation might be premature. *Computed tomography of head without contrast* - While altered mental status can be caused by intracranial pathology, the sudden onset of symptoms coupled with the recent surgery and classic signs of opioid overdose makes a **head CT** less urgent than immediate medication to reverse potential overdose. - The **anisocoria** could be related to prior cataract surgery (irregular pupil) rather than acute neurological insult, and the fixed 1mm pupil is concerning but reversible with naloxone if opioid-induced. *Orange juice by mouth* - The patient's fingerstick glucose is 79, which is within the normal range, ruling out **hypoglycemia** as the cause of her altered mental status. - Giving fluids or sustenance by mouth to a patient with altered mental status and depressed consciousness carries a significant risk of **aspiration**.

Question 15: A 34-year-old woman presents to the office with weight gain despite her dietary modifications. She also says she has associated constipation and feels she has no energy. She says she often feels the ambient temperature is too cold these days. Her past medical history is insignificant. Her blood pressure is 140/85 mm Hg, the pulse is 60/min, the temperature is 36.7°C (98.0°F), and the respirations are 22/min. On physical examination, deep tendon reflexes are 1+ at the right ankle, which has a delayed relaxation phase. A hormone deficiency disorder is suspected and blood samples are sent to the lab for investigation. The laboratory report confirms the suspicion, and the patient is prescribed a synthetic hormone. How does this hormone most likely act to produce its cellular effects?

A. Binds to a nuclear receptor (Correct Answer)
B. Activates tyrosine kinase
C. Increases intake of iodine by thyroid cells
D. Increases cyclic adenosine monophosphate (cAMP)
E. Increases activity of phospholipase C

Explanation: ***Binds to a nuclear receptor*** - The patient's symptoms (weight gain, constipation, fatigue, cold intolerance, bradycardia, and delayed deep tendon reflex relaxation) are classic for **hypothyroidism**. - The synthetic hormone prescribed is likely **levothyroxine** (synthetic T4), which, after conversion to T3, acts by binding to **nuclear receptors** to modulate gene expression. *Activates tyrosine kinase* - **Tyrosine kinase receptors** are typically activated by growth factors and insulin, triggering intracellular signaling cascades, which is not the primary mechanism for thyroid hormones. - This mechanism involves phosphorylation of tyrosine residues on target proteins and is seen with hormones like **insulin and growth hormone**. *Increases intake of iodine by thyroid cells* - This describes the action of **TSH (thyroid-stimulating hormone)** on thyroid follicular cells to produce thyroid hormones. - It is not the mechanism by which synthetic thyroid hormone exerts its cellular effects. *Increases cyclic adenosine monophosphate (cAMP)* - **cAMP** is a second messenger involved in signaling pathways for many hormones that act on **G-protein-coupled receptors** (e.g., glucagon, epinephrine). - This is not the primary mechanism of action for thyroid hormones. *Increases activity of phospholipase C* - Activation of **phospholipase C** leads to the production of **inositol triphosphate (IP3)** and **diacylglycerol (DAG)**, which are second messengers involved in calcium signaling. - This mechanism is characteristic of hormones like **TRH (thyrotropin-releasing hormone)** and **GnRH (gonadotropin-releasing hormone)**, not thyroid hormones.

Question 16: A 24-year-old man presents with a history of intermittent fever for the last 2 days. He says his episodes of fever are accompanied by shaking and chills. He mentions that his father has been recently recovered from chloroquine-resistant P. falciparum malaria, which was treated successfully with quinine. On physical examination, his temperature is 38.9°C (102°F), pulse rate is 110/min, blood pressure is 116/80 mm Hg, and respiratory rate is 18/min. Examination of his abdomen reveals splenomegaly. His blood sample is sent for the examination of the peripheral smear, which confirms the diagnosis of Plasmodium falciparum malaria. The patient is placed on treatment with oral quinine. After 5 days, the patient returns with improved symptoms of malaria but with complaints of a headache, tinnitus, nausea, and dizziness. The patient mentions that he has been taking a drug for the last 3 months to control his dyspepsia symptoms. Which of the following drugs is most likely to have caused the above-mentioned symptoms in this patient?

A. Famotidine
B. Ranitidine
C. Cimetidine (Correct Answer)
D. Sucralfate
E. Pantoprazole

Explanation: ***Cimetidine*** - The patient is experiencing symptoms of **cinchonism** (headache, tinnitus, nausea, dizziness) due to **quinine** treatment for *P. falciparum* malaria. - **Cimetidine** inhibits the **CYP450 enzyme system**, which is responsible for quinine metabolism. This inhibition leads to increased **quinine levels** and enhanced toxicity. *Famotidine* - **Famotidine** is an H2-receptor antagonist that does not significantly inhibit the **CYP450 enzyme system**. - It would not lead to elevated quinine levels or cinchonism. *Ranitidine* - **Ranitidine** is an H2-receptor antagonist that has minimal or no inhibitory effect on the **CYP450 enzyme system**. - Therefore, it would not increase quinine levels to cause toxicity. *Sucralfate* - **Sucralfate** is a mucosal protective agent that forms a viscous gel, binding to ulcerated tissue. - It does not undergo systemic absorption or interact with the **CYP450 system**, thus having no effect on quinine metabolism. *Pantoprazole* - **Pantoprazole** is a proton pump inhibitor that, while metabolized by CYP2C19 and CYP3A4, does not significantly inhibit these enzymes to increase quinine levels. - It is unlikely to cause the described drug interaction.

Question 17: An 81-year-old woman is brought to the physician by her son because of worsening forgetfulness and disorientation over the past 2 years. She has to be reminded of her grandchildren's names and frequently forgets her current address. She lives with her son. She has occasional episodes of urinary incontinence. She appears well nourished. Neurologic examination shows no abnormalities; her gait is normal. Mental status examination shows mild memory impairment. She is oriented to self and place, but not to time. Which of the following is the most appropriate pharmacotherapy?

A. Acetazolamide
B. Levodopa and carbidopa
C. Thiamine
D. Galantamine (Correct Answer)
E. Perphenazine

Explanation: ***Galantamine*** - This patient presents with **progressive memory impairment** and **disorientation** over two years, suggestive of Alzheimer's dementia, even with a normal neurologic exam and gait. - **Galantamine** is an **acetylcholinesterase inhibitor** used to treat mild to moderate Alzheimer's dementia by increasing acetylcholine levels in the brain. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** primarily used as a diuretic, for glaucoma, or to treat altitude sickness. - It has no role in the direct treatment of dementia and would not address the underlying cognitive decline. *Levodopa and carbidopa* - **Levodopa and carbidopa** are used to treat **Parkinson's disease**, which is characterized by motor symptoms like tremor, rigidity, and bradykinesia. - The patient's neurologic examination, including gait, is normal, ruling out typical Parkinsonian features. *Thiamine* - **Thiamine** (vitamin B1) is used to treat **Wernicke-Korsakoff syndrome**, which is often seen in individuals with chronic alcohol abuse and presents with confusion, ataxia, and ophthalmoplegia. - This patient's presentation does not align with Wernicke-Korsakoff syndrome, and she is described as well-nourished. *Perphenazine* - **Perphenazine** is a **first-generation antipsychotic** used to treat psychotic disorders like schizophrenia or severe agitation. - There is no indication of psychosis or severe agitation in this patient; antipsychotics are generally avoided in elderly patients with dementia due to increased mortality risk.

Question 18: A 57-year-old woman presents complaining of feeling sleepy all the time. She reports having an uncontrollable urge to take multiple naps during the day and sometimes sees strange shadows in front of her before falling asleep. Although she awakens feeling refreshed and energized, she often finds herself ‘stuck’ and cannot move for a while after waking up. She also mentions she is overweight and has failed to lose weight despite multiple attempts at dieting and using exercise programs. No significant past medical history. No current medications. The patient denies smoking, alcohol consumption, or recreational drug usage. Family history reveals that both her parents were overweight, and her father had hypertension. Her vital signs include: pulse 84/min, respiratory rate 16/min, and blood pressure 128/84 mm Hg. Her body mass index (BMI) is 36 kg/m2. Physical examination is unremarkable. Which of the following medications is the best course of treatment in this patient?

A. Methylphenidate (Correct Answer)
B. Orlistat
C. Alprazolam
D. Melatonin
E. Continuous positive airway pressure (CPAP)

Explanation: ***Methylphenidate*** - The patient presents with the **classic tetrad of narcolepsy**: excessive daytime sleepiness, sleep paralysis (cannot move after waking), hypnagogic hallucinations (seeing shadows before sleep), and the urge to take multiple naps despite waking refreshed. - **Methylphenidate** is a **CNS stimulant** and first-line pharmacological treatment for **narcolepsy**, effectively reducing excessive daytime sleepiness by increasing dopamine and norepinephrine in the CNS. - While obesity is a risk factor for obstructive sleep apnea, the patient's **refreshed awakening** and **specific narcoleptic symptoms** (sleep paralysis and hallucinations) make narcolepsy the primary diagnosis requiring treatment. *Continuous positive airway pressure (CPAP)* - CPAP is the treatment for **obstructive sleep apnea (OSA)**, not narcolepsy. - While the patient's obesity increases OSA risk, OSA patients typically wake **unrefreshed**, not energized as this patient reports. - Additionally, **sleep paralysis and hypnagogic hallucinations are NOT features of OSA**—they are specific to narcolepsy. - Most importantly, **CPAP is not a medication** as requested in the question stem. *Orlistat* - **Orlistat** is a lipase inhibitor used for **obesity management**. - While weight loss could help if OSA were present, it does not address the primary narcolepsy symptoms and is not appropriate first-line treatment for the acute presentation. *Alprazolam* - **Alprazolam** is a benzodiazepine used for **anxiety disorders**. - It would **worsen daytime sleepiness** and is contraindicated in patients with sleep disorders as it depresses the CNS and can worsen both narcolepsy and potential sleep apnea. *Melatonin* - **Melatonin** regulates the **sleep-wake cycle** and is used for insomnia or circadian rhythm disorders. - It does not treat excessive daytime sleepiness, sleep paralysis, or hypnagogic hallucinations characteristic of narcolepsy.

Question 19: A 57-year-old man is brought to the emergency department by his son for odd behavior. The patient and his son had planned to go on a hike today. On the drive up to the mountain, the patient began acting strangely which prompted the patient's son to bring him in. The patient has a past medical history of constipation, seasonal allergies, alcohol abuse, and IV drug abuse. His current medications include diphenhydramine, metoprolol, and disulfiram. The patient's son states he has been with the patient all morning and has only seen him take his over the counter medications and eat breakfast. His temperature is 102.0°F (38.9°C), blood pressure is 147/102 mmHg, pulse is 110/min, and oxygen saturation is 98% on room air. The patient appears uncomfortable. Physical exam is notable for tachycardia. The patient's skin appears dry, red, and flushed, and he is confused and not responding to questions appropriately. Which of the following is the best treatment for this patient's condition?

A. Naloxone
B. IV fluids, thiamine, and dextrose
C. Physostigmine (Correct Answer)
D. Atropine
E. Neostigmine

Explanation: ***Physostigmine*** - The patient's symptoms (fever, tachycardia, hypertension, dry flushed skin, confusion, and agitation) are classic for **anticholinergic toxicity**, likely caused by **diphenhydramine**. - **Physostigmine** is a reversible **acetylcholinesterase inhibitor** that crosses the blood-brain barrier, effectively counteracting both peripheral and central anticholinergic effects. *Naloxone* - **Naloxone** is used to reverse **opioid overdose**, which typically presents with **respiratory depression** and miosis, not seen here. - While the patient has a history of IV drug abuse, the clinical picture does not align with opioid intoxication. *IV fluids, thiamine, and dextrose* - This combination is standard empirical treatment for altered mental status in patients with suspected **alcohol abuse** or **nutritional deficiencies**. - While the patient has a history of alcohol abuse, his primary presentation points more specifically to anticholinergic toxicity. *Atropine* - **Atropine** is an **anticholinergic agent**; administering it would worsen the patient's already present anticholinergic toxicity. - It is used to treat cholinergic crises, such as organophosphate poisoning, by blocking acetylcholine receptors. *Neostigmine* - **Neostigmine** is an **acetylcholinesterase inhibitor** but does **not cross the blood-brain barrier**, meaning it would only address peripheral cholinergic effects and not the patient's central nervous system symptoms like confusion. - It is often used for myasthenia gravis or reversal of neuromuscular blockade.

Question 20: A 7-year-old boy is rushed to the emergency room after developing severe abdominal pain with nausea and vomiting for a day at a summer camp. He also has a bad cough and generalized muscle weakness. He was doing fine until these symptoms started on day 3 of his camp. Past medical history obtained from his parents on the phone was significant for recurrent nephrotic syndrome controlled by prolonged corticosteroid therapy. His blood pressure is 110/75 mm Hg, axillary temperature is 38.9°C (102.0°F) and random blood sugar is 49 mg/dL. On examination, he appears somnolent. His heart has a regular rate and rhythm and his lungs have rhonchi and focal wheezing, bilaterally. Results of other lab investigations are: Sodium 131 mEq/L Potassium 5.1 mEq/L Chloride 94 mEq/L Bicarbonate 16 mEq/L Urea 44 mg/dL Creatinine 1.4 mg/dL A respiratory culture is positive for type A influenza. Which of the following is most likely to be the predisposing cause of the patient’s symptoms?

A. Iatrogenic suppression of a trophic effect on the adrenal glands (Correct Answer)
B. An extremely virulent form of Influenza
C. Bilateral hemorrhagic necrosis of the adrenal glands
D. Primary adrenal insufficiency
E. Immunosuppression

Explanation: **Iatrogenic suppression of a trophic effect on the adrenal glands** - The patient's history of **prolonged corticosteroid therapy** for recurrent nephrotic syndrome likely led to **iatrogenic adrenal suppression**. This means the adrenal glands, specifically the cortex, became atrophic due to the exogenous corticosteroids, which inhibit **ACTH** (adrenocorticotropic hormone) release from the pituitary. - The stress of influenza infection, coupled with suppressed adrenal function, can precipitate an **adrenal crisis**, characterized by **hypotension**, **hypoglycemia**, **hyponatremia**, **hyperkalemia**, and gastrointestinal symptoms, which are all present in this patient. *An extremely virulent form of Influenza* - While the patient has influenza, the constellation of symptoms, particularly **hypoglycemia**, **electrolyte abnormalities** (low sodium, high potassium), and a history of prolonged corticosteroid use, points beyond typical influenza severity. - Influenza alone would not typically cause such profound metabolic disturbances and adrenal crisis in an otherwise healthy child. *Bilateral hemorrhagic necrosis of the adrenal glands* - This condition, known as **Waterhouse-Friderichsen syndrome**, is typically associated with **fulminant meningococcemia** or other severe bacterial sepsis, not primarily with influenza. - While it can cause adrenal crisis, the clinical picture here is more consistent with chronic adrenal insufficiency unmasked by acute stress, given the corticosteroid history. *Primary adrenal insufficiency* - **Primary adrenal insufficiency** (e.g., Addison's disease) involves direct damage to the adrenal glands and would typically present with **hyperpigmentation** due to elevated ACTH, which is not mentioned. - While the symptoms mimic adrenal crisis, the underlying cause in this case is likely **secondary adrenal insufficiency** due to exogenous steroid use, rather than primary destruction of the adrenal cortex. *Immunosuppression* - While prolonged corticosteroid therapy does cause **immunosuppression**, making the child more susceptible to infections like influenza, immunosuppression itself is not the direct predisposing cause of the acute **adrenal crisis** symptoms (abdominal pain, hypoglycemia, electrolyte imbalances). - The critical link between the corticosteroid history and the current symptoms is the suppression of adrenal function, not merely the increased risk of infection.

Question 21: A previously healthy 13-year-old boy is brought to the emergency department by his parents for the evaluation of several episodes of vomiting since this morning. He reports nausea and severe headache. Over the past four days, he has had fever, a runny nose, and a sore throat. His mother gave him an analgesic drug that she uses for rheumatoid arthritis. He has not had any trauma. Last month, the patient traveled to Mexico with his family. He is at the 85th percentile for height and 25th percentile for weight. He appears weak. His temperature is 38°C (100°F), pulse is 90/min, respirations are 18/min, and blood pressure is 100/60 mm Hg. Mental status examination shows psychomotor agitation alternating with lethargy. Examination shows bilateral optic disc swelling. Serum studies show: Urea nitrogen 30 mg/dL Glucose 70 mg/dL Aspartate aminotransferase (AST, GOT) 60 U/L Alanine aminotransferase (ALT, GPT) 60 U/L Arterial blood gas analysis on room air shows a pH of 7.30. Which of the following is the most likely cause of this patient's symptoms?

A. Infection with hepatitis A virus
B. Reye syndrome (Correct Answer)
C. Autoimmune destruction of pancreatic beta cells
D. Ruptured aneurysm in the circle of Willis
E. Antifreeze ingestion

Explanation: ***Reye syndrome*** - The combination of a recent **viral illness** (fever, runny nose, sore throat) treated with an **analgesic used for rheumatoid arthritis** (likely aspirin), followed by **encephalopathy** (psychomotor agitation, lethargy, severe headache, vomiting, optic disc swelling) and **liver dysfunction** (elevated AST/ALT, elevated urea nitrogen, acidosis), is highly characteristic of Reye syndrome. - This syndrome is particularly associated with **aspirin use in children** recovering from viral infections, leading to mitochondrial damage in the liver and brain. *Infection with hepatitis A virus* - While hepatitis A can cause **nausea, vomiting**, and **elevated liver enzymes**, it is less likely to cause the severe neurological symptoms and metabolic derangements seen here, such as **optic disc swelling** and **acidosis**. - The history of aspirin use after a viral illness points more strongly towards Reye syndrome over hepatitis A, despite a travel history to Mexico. *Autoimmune destruction of pancreatic beta cells* - This describes **Type 1 diabetes mellitus**, which would present with symptoms like **polyuria, polydipsia, weight loss**, and sometimes diabetic ketoacidosis. - The patient's presentation with acute encephalopathy, liver dysfunction, and a normal blood glucose level makes this diagnosis unlikely. *Ruptured aneurysm in the circle of Willis* - A ruptured aneurysm would cause a **sudden, severe headache** and neurological deficits, but it would not explain the preceding viral illness, the **liver enzyme elevations**, or the **metabolic acidosis**. - While optic disc swelling can occur with increased intracranial pressure, the overall clinical picture does not align. *Antifreeze ingestion* - Antifreeze (ethylene glycol) ingestion causes **severe metabolic acidosis** with a high anion gap, **renal failure**, and neurological symptoms. - While it can explain the acidosis and altered mental status, there is **no history of exposure** and it would not account for the preceding viral illness or the specific pattern of liver enzyme elevation associated with Reye syndrome.

Question 22: A 59-year-old man comes to your clinic accompanied by his wife complaining of nausea and dizziness. He reports that he is unsure when his symptoms started, but they have been affecting him for “a while.” It began as episodes of “unsteadiness” and progressed to a feeling of “spinning.” He cannot tell if his symptoms change with position, but reports that if he does not lie down he will become nauseous. When asked about other symptoms, his wife reports that she has also noticed the patient has worsening hearing loss. She complains that she is constantly repeating herself, especially if she speaks on his right side. The patient denies this and says that she just speaks too softly. The patient’s past medical history is significant for hypertension, alcoholism, and chronic obstructive pulmonary disease. His medications include aspirin, amlodipine, and fluticasone-salmeterol. He reports he drinks a glass of red wine every night with dinner and smokes a cigar on the weekends. Examination shows delayed horizontal nystagmus. Which of the following is the first-line treatment?

A. CN VIII ablation
B. Epley maneuver
C. Thiamine
D. Low-salt diet
E. Meclizine (Correct Answer)

Explanation: ***Meclizine*** - The patient exhibits classic symptoms of **Meniere's disease**, including **vertigo**, **nausea**, and **unilateral hearing loss**, often accompanied by nystagmus. Meclizine is a first-line **antihistamine** commonly used for symptomatic relief of vertigo. - Meclizine works by decreasing excitability of the inner ear labyrinth and blocking chemoreceptor trigger zone, thus alleviating **dizziness** and **nausea**. *CN VIII ablation* - **CN VIII ablation** (vestibular nerve section) is a **surgical procedure** considered only in severe, debilitating cases of **Meniere's disease** that are unresponsive to all other medical treatments. - It is a **destructive procedure** that carries risks such as further hearing loss or facial nerve injury and is not a first-line treatment. *Epley maneuver* - The **Epley maneuver** is a repositioning technique used specifically to treat **benign paroxysmal positional vertigo (BPPV)**, which is caused by dislodged otoconia. - While the patient has vertigo, the presence of **hearing loss** and progressive symptoms points away from BPPV, and the nystagmus is described as delayed horizontal, not typically characteristic of BPPV. *Thiamine* - **Thiamine** (vitamin B1) supplementation is primarily indicated for patients with **Wernicke-Korsakoff syndrome** due to chronic alcohol abuse, presenting with ataxia, confusion, and ophthalmoplegia. - While the patient has a history of **alcoholism**, his dominant symptoms of **vertigo** and **hearing loss** are not directly addressed by thiamine, and there's no indication of acute Wernicke's encephalopathy. *Low-salt diet* - A **low-salt diet** is a common **lifestyle modification** recommended for patients with **Meniere's disease** to help reduce fluid retention in the inner ear. - While it can be part of the long-term management, it is a **preventative/symptomatic control measure** rather than an immediate first-line pharmacological treatment for acute symptoms like severe nausea and dizziness.

Question 23: A 9-year-old boy is brought to the clinic by his dad for an annual well-child exam. The boy was diagnosed with ADHD at an outside clinic and has been on methylphenidate for symptom management for the past year. The father reports that the patient is more energetic but that his teacher still complains of him "spacing out" during class. The patient reports that it is difficult to follow in class sometimes because the teacher would just "skip ahead suddenly." He denies any headaches, vision changes, fever, or abdominal pain, but endorses decreased appetite since starting methylphenidate. What is the mechanism of action of the drug that would be most appropriate to continue for this patient's ADHD management?

A. Increase in the frequency of chloride channel opening
B. Increase in duration of chloride channel opening
C. Blockage of voltage-gated sodium channels and inhibition of glutamate release
D. Blockage of thalamic T-type calcium channels
E. Blockage of dopamine and norepinephrine reuptake (Correct Answer)

Explanation: ***Blockage of dopamine and norepinephrine reuptake*** - **Methylphenidate** (Ritalin) is a central nervous system stimulant that primarily works by **blocking the reuptake of dopamine and norepinephrine** into the presynaptic neuron, increasing their concentration in the synaptic cleft. - This mechanism enhances **neurotransmission** in brain regions associated with attention and executive function, which are often impaired in ADHD. *Increase in the frequency of chloride channel opening* - This mechanism of action is characteristic of **benzodiazepines**, which are positive allosteric modulators of **GABA-A receptors**. - Benzodiazepines are typically used for anxiety or seizure disorders, not for the treatment of ADHD. *Increase in duration of chloride channel opening* - This mechanism is characteristic of **barbiturates**, which also act on **GABA-A receptors** but increase the **duration** of chloride channel opening. - Barbiturates have sedative effects and are used for conditions like seizure control and anesthesia, not ADHD. *Blockage of voltage-gated sodium channels and inhibition of glutamate release* - This mechanism is typical of some **antiepileptic drugs** like **lamotrigine** or **valproic acid**. - These drugs are used to treat seizures and certain mood disorders, and are not the primary mechanism for first-line ADHD medications like methylphenidate. *Blockage of thalamic T-type calcium channels* - This mechanism is characteristic of **ethosuximide**, an anti-epileptic drug specifically used to treat **absence seizures**. - This is not the mechanism of action for drugs used to manage ADHD.

Question 24: Two weeks after hospitalization for acute psychosis, a 27-year-old woman with a history of paranoid schizophrenia comes to the physician because of difficulty walking and shaking movements of her hands. Current medications include fluphenazine, which was started during her recent hospitalization. Examination shows a shuffling gait, rigidity in the upper extremities, and a low-amplitude tremor of her hands that improves with activity. Mental status examination shows no abnormalities. Treatment with a drug with which of the following mechanisms of action is most likely to provide relief for this patient's current symptoms?

A. GABA agonist
B. β-adrenergic antagonist
C. Dopamine antagonist
D. Histamine antagonist
E. Muscarinic antagonist (Correct Answer)

Explanation: ***Muscarinic antagonist*** - The patient exhibits classic symptoms of **drug-induced parkinsonism** (shuffling gait, rigidity, tremor) due to the antipsychotic **fluphenazine**. - **Muscarinic antagonists** (e.g., benztropine, trihexyphenidyl) are effective in treating these **extrapyramidal symptoms (EPS)** by restoring the dopamine-acetylcholine balance in the basal ganglia. *GABA agonist* - **GABA agonists** (e.g., benzodiazepines) are primarily used for anxiety, seizures, and insomnia, and are not indicated for drug-induced parkinsonism. - While they can have muscle relaxant properties, they do not specifically target the underlying neurochemical imbalance responsible for the patient's symptoms. *β-adrenergic antagonist* - **β-adrenergic antagonists** (e.g., propranolol) are typically used to treat **akathisia** (motor restlessness), another form of EPS, or essential tremor, not the parkinsonian symptoms described. - They work by blocking peripheral β-receptors, which can reduce anxiety and tremor, but not the rigidity or bradykinesia of parkinsonism. *Dopamine antagonist* - **Dopamine antagonists** are the **cause** of the patient's symptoms as fluphenazine is a dopamine D2 receptor antagonist. - Further antagonism of dopamine would **exacerbate** rather than alleviate the extrapyramidal symptoms. *Histamine antagonist* - **Histamine antagonists** (e.g., diphenhydramine) can have anticholinergic properties and might provide some relief, but they are not the primary or most effective treatment for drug-induced parkinsonism compared to direct muscarinic antagonists. - Their primary role is in allergic reactions and sedation, and their anticholinergic effect is often a side effect rather than a targeted therapeutic action for EPS.

Question 25: A 26-year-old man is brought to the emergency department because of abdominal pain, dizziness, shortness of breath, and swelling and pruritus of the lips, tongue, and throat for 1 hour. The symptoms began minutes after he started eating a lobster dinner. It is determined that his symptoms are due to surface crosslinking of IgE. This immunologic event most likely caused the release of which of the following?

A. Cathepsin
B. Tryptase (Correct Answer)
C. Bradykinin
D. Interferon gamma
E. Serotonin

Explanation: ***Tryptase*** - The patient's symptoms (abdominal pain, dizziness, shortness of breath, lip/tongue/throat swelling, pruritus) after eating lobster are classic for an **IgE-mediated allergic reaction**, specifically **anaphylaxis**. - **Tryptase** is a serine protease predominantly stored in and released from the **granules of mast cells** during allergic reactions, making it an excellent biomarker for mast cell activation. *Cathepsin* - Cathepsins are a group of proteases found in lysosomes and play a role in protein degradation. They are not primary mediators of immediate hypersensitivity reactions. - While involved in some immune processes, cathepsins are not typically released in significant amounts during IgE-mediated anaphylaxis. *Bradykinin* - Bradykinin is a potent vasodilator and pain-producing peptide, but it is primarily involved in pathways like the **kallikrein-kinin system** and hereditary angioedema, not directly released by IgE crosslinking on mast cells. - While it contributes to symptoms like angioedema, it is not a direct mediator released upon mast cell degranulation in anaphylaxis. *Interferon gamma* - **Interferon gamma (IFN-γ)** is a cytokine primarily produced by T lymphocytes and NK cells, essential for antiviral and antitumor immunity, and macrophage activation. - It is a key mediator of **Th1-type immune responses** and is not involved in the immediate degranulation of mast cells in an IgE-mediated allergic reaction. *Serotonin* - Serotonin (5-hydroxytryptamine) is a neurotransmitter and vasoconstrictor found in platelets and the gastrointestinal tract, and also released by mast cells in some species. - While human mast cells contain some serotonin, its contribution to systemic anaphylaxis in humans is generally considered less significant compared to histamine and other potent mediators.

Question 26: A 28-year-old female presents to her primary care doctor complaining of new onset blurry vision. She first noticed her vision getting blurry toward the end of the day several days ago. Since then, she reports that her vision has been fine when she wakes up but gets worse throughout the day. She has also noticed that her eyelids have started to droop before she goes to bed. On exam, she has bilateral ptosis that is worse on the right. Administering edrophonium to this patient leads to an immediate improvement in her symptoms. Which of the following is most likely true about this patient’s condition?

A. It is caused by a type III hypersensitivity reaction
B. It is associated with a neoplasm of lung neuroendocrine cells
C. It is caused by antibodies directed against presynaptic P/Q calcium channels
D. An increasing response will be seen on repeated nerve stimulation
E. It is associated with a benign proliferation of epithelial cells of the thymus (Correct Answer)

Explanation: ***It is associated with a benign proliferation of epithelial cells of the thymus*** - The patient's symptoms of progressive weakness throughout the day, ptosis, and improvement with edrophonium (an acetylcholinesterase inhibitor) are highly suggestive of **myasthenia gravis**. - Approximately 75% of patients with myasthenia gravis have **thymic abnormalities**, with about 65% having **thymic hyperplasia** (a benign proliferation of epithelial cells) and 10% having a **thymoma**. *It is caused by a type III hypersensitivity reaction* - **Type III hypersensitivity reactions** involve immune complex deposition, as seen in diseases like Systemic Lupus Erythematosus or post-streptococcal glomerulonephritis. - Myasthenia gravis is a **Type II hypersensitivity reaction**, where antibodies directly target specific cell surface antigens, in this case, acetylcholine receptors at the neuromuscular junction. *It is associated with a neoplasm of lung neuroendocrine cells* - A neoplasm of **lung neuroendocrine cells**, specifically **small cell lung carcinoma**, is associated with **Lambert-Eaton Myasthenic Syndrome (LEMS)**. - LEMS presents with proximal muscle weakness that *improves* with activity, unlike the fatiguable weakness seen in myasthenia gravis. *It is caused by antibodies directed against presynaptic P/Q calcium channels* - Antibodies directed against **presynaptic P/Q calcium channels** are characteristic of **Lambert-Eaton Myasthenic Syndrome (LEMS)**. - In LEMS, these antibodies reduce the release of acetylcholine into the synaptic cleft, leading to muscle weakness. *An increasing response will be seen on repeated nerve stimulation* - An **increasing (incremental) response** on repeated nerve stimulation is a characteristic finding in **Lambert-Eaton Myasthenic Syndrome (LEMS)**. - In myasthenia gravis, repeated nerve stimulation typically shows a **decreasing (decremental) response** due to the depletion of functionally available acetylcholine receptors.

Question 27: A 62-year-old woman comes to the physician for a follow-up examination after a recent change in her medication regimen. She reports that she feels well. She has type 2 diabetes mellitus, hyperlipidemia, hypertension, essential tremor, and chronic back pain. Current medications are metformin, glyburide, propranolol, simvastatin, ramipril, amitriptyline, and ibuprofen. Fingerstick blood glucose concentration is 47 mg/dL. Serum studies confirm this value. Which of the following pharmacologic mechanisms is most likely responsible for the absence of symptoms in this patient?

A. Antagonism at β2-adrenergic receptors (Correct Answer)
B. Blockade of potassium channels in pancreatic β-cells
C. Inhibition of HMG-CoA reductase
D. Inhibition of angiotensin-converting enzyme
E. Inhibition of norepinephrine and serotonin reuptake

Explanation: ***Antagonism at β2-adrenergic receptors*** - The patient is taking **propranolol**, a **non-selective beta-blocker**, for essential tremor. Propranolol blocks both β1 and β2-adrenergic receptors. - The typical **adrenergic warning symptoms of hypoglycemia** are mediated by β-adrenergic activation: tremor and anxiety (β2-mediated), and palpitations/tachycardia (β1-mediated). - By blocking **β2 receptors** (and β1), propranolol **masks these hypoglycemia symptoms**, preventing the patient from recognizing dangerously low blood sugar (47 mg/dL). - This is a clinically important drug interaction: **non-selective beta-blockers can mask hypoglycemia** in diabetic patients, particularly those on sulfonylureas like glyburide. *Blockade of potassium channels in pancreatic β-cells* - This mechanism describes the action of **sulfonylureas** like **glyburide**, which close ATP-sensitive potassium channels on pancreatic beta cells, causing depolarization and insulin release. - Glyburide is the **likely cause** of this patient's hypoglycemia by increasing insulin secretion. - However, this mechanism *causes* the hypoglycemia; it does not mask or prevent the symptoms of hypoglycemia. *Inhibition of HMG-CoA reductase* - This is the mechanism of action for **statins** like **simvastatin**, used to treat hyperlipidemia. - Statins inhibit the rate-limiting enzyme in cholesterol synthesis and have **no direct effect** on blood glucose levels or the symptoms of hypoglycemia. *Inhibition of angiotensin-converting enzyme* - This describes the action of **ACE inhibitors** like **ramipril**, used to treat hypertension. - ACE inhibitors primarily affect the **renin-angiotensin-aldosterone system** and blood pressure regulation. - They do not mask hypoglycemia symptoms, though they may rarely potentiate hypoglycemia through improved insulin sensitivity. *Inhibition of norepinephrine and serotonin reuptake* - This is the mechanism of action for **tricyclic antidepressants (TCAs)** like **amitriptyline**, used for chronic pain in this patient. - While TCAs have anticholinergic effects and can affect the autonomic nervous system, they do **not mask adrenergic hypoglycemia symptoms**. - Amitriptyline does not significantly affect glucose metabolism or the sympathetic response to hypoglycemia.

Question 28: A 29-year-old man comes to the physician for worsening restlessness over the past several days. Three weeks ago, he was started on trifluoperazine for the treatment of schizophrenia. He reports that, since then, he has often felt compelled to pace around his house and is unable to sit or stand still. He is switched to an alternative antipsychotic medication. Four weeks later, the patient reports improvement of his symptoms but says that he has developed increased drowsiness, blurred vision, and dry mouth. The patient was most likely switched to which of the following drugs?

A. Fluphenazine
B. Metoclopramide
C. Haloperidol
D. Chlorpromazine (Correct Answer)
E. Trimipramine

Explanation: ***Chlorpromazine*** - **Chlorpromazine** is a **first-generation antipsychotic** that belongs to the **low-potency** class, meaning it has a lower risk of extrapyramidal symptoms (EPS) but a higher risk of anticholinergic side effects. - The patient's initial symptoms of restlessness (akathisia) after starting **trifluoperazine** (a high-potency FGA) strongly suggest EPS. Switching to chlorpromazine would alleviate EPS but would likely cause the reported **drowsiness, blurred vision, and dry mouth** due to its significant **antihistaminic**, **anticholinergic**, and **alpha-1 adrenergic blocking effects**. *Fluphenazine* - **Fluphenazine** is a **high-potency first-generation antipsychotic**, similar to trifluoperazine. - Switching to fluphenazine from trifluoperazine would likely **exacerbate or maintain** the patient's extrapyramidal symptoms, not alleviate them. *Metoclopramide* - **Metoclopramide** is a **dopamine receptor antagonist** primarily used as an antiemetic and prokinetic agent. - While it can cause side effects similar to antipsychotics, it is **not an antipsychotic** medication used for schizophrenia and would not be an appropriate switch for symptom control. *Haloperidol* - **Haloperidol** is another **high-potency first-generation antipsychotic**, known for a high incidence of extrapyramidal symptoms. - Switching to haloperidol would likely **worsen** the patient's akathisia and other EPS rather than improve them. *Trimipramine* - **Trimipramine** is a **tricyclic antidepressant**, not an antipsychotic, and is typically used for depression and anxiety. - It would not treat schizophrenia and while it has anticholinergic effects, it would not explain the improvement in akathisia in an antipsychotic context.

Question 29: A 27-year-old man is brought to the emergency department by his girlfriend. The patient is a seasonal farm worker and was found laying down and minimally responsive under a tree. The patient was immediately brought to the emergency department. The patient has a past medical history of IV drug use, marijuana use, and alcohol use. His current medications include ibuprofen. His temperature is 98.2°F (36.8°C), blood pressure is 100/55 mmHg, pulse is 60/min, respirations are 15/min, and oxygen saturation is 98% on room air. On physical exam, the patient's extremities are twitching, and his clothes are soaked in urine and partially removed. The patient is also drooling and coughs regularly. Which of the following is the best next step in management?

A. Atropine (Correct Answer)
B. Electroencephalography
C. Urine toxicology
D. Supportive therapy and monitoring
E. Lorazepam

Explanation: ***Atropine*** - The patient's symptoms (twitching, drooling, urinary incontinence, bradycardia, hypotension, and bronchorrhea evidenced by regular coughing) are classic for **organophosphate poisoning**, which causes a **cholinergic crisis**. - **Atropine** is the primary antidote, acting as a competitive antagonist at **muscarinic acetylcholine receptors**, and is crucial for reversing severe cholinergic symptoms. *Electroencephalography* - While seizures can occur with some toxic ingestions, an **EEG** is not the immediate priority given the clear signs of cholinergic toxicity and the need for rapid antidotal therapy. - An EEG might be considered later if the cause of neurological symptoms remains unclear or to assess for non-convulsive status epilepticus. *Urine toxicology* - While a **urine toxicology screen** could be useful for identifying other potential substances, the clinical presentation is highly suggestive of **organophosphate poisoning**, and immediate action with an antidote is more critical than waiting for lab results. - Delaying specific treatment for presumptive toxicology results could be detrimental to the patient's outcome. *Supportive therapy and monitoring* - **Supportive care** (e.g., airway management, intravenous fluids) is always important, but in this specific scenario, a targeted antidote is required to address the underlying toxicity effectively. - Relying solely on monitoring without administering specific treatment would allow the patient's cholinergic crisis to worsen, potentially leading to respiratory failure. *Lorazepam* - **Lorazepam** is a benzodiazepine used to treat seizures and agitation. While the patient has twitching, this is likely part of the cholinergic crisis and not necessarily a primary seizure disorder. - **Lorazepam** would not address the fundamental cholinergic overload and would not be the best first-line treatment compared to **atropine** for organophosphate poisoning.

Question 30: A 50-year-old man is brought to the emergency department by his wife with acute onset confusion, disorientation, and agitation. The patient's wife reports that he has diabetic gastroparesis for which he takes domperidone in 3 divided doses every day. He also takes insulin glargine and insulin lispro for management of type 1 diabetes mellitus and telmisartan for control of hypertension. Today, she says the patient forgot to take his morning dose of domperidone to work and instead took 4 tablets of scopolamine provided to him by a coworker. Upon returning home after 4 hours, he complained of dizziness and became increasingly drowsy and confused. His temperature is 38.9°C (102.0°F), pulse rate is 112 /min, blood pressure is 140/96 mm Hg, and respiratory rate is 20/min. On physical examination, the skin is dry. Pupils are dilated. There are myoclonic jerks of the jaw present. Which of the following is the most likely cause of this patient’s symptoms?

A. Hypoglycemia
B. Domperidone overdose
C. Diabetic ketoacidosis
D. Heatstroke
E. Scopolamine overdose (Correct Answer)

Explanation: ***Scopolamine overdose*** - The patient exhibits classic signs of **anticholinergic toxicity**, including acute onset confusion, disorientation, agitation, dilated pupils, dry skin, fever, and tachycardia. **Scopolamine** is a potent anticholinergic agent. - The history of taking four tablets of scopolamine, especially after forgetting his domperidone (which is a dopamine receptor antagonist, indirectly affecting cholinergic tone), strongly points to an overdose. *Hypoglycemia* - While confusion and dizziness can be symptoms of **hypoglycemia**, the presence of dilated pupils, dry skin, fever, and agitation are inconsistent with this diagnosis. - Patients with hypoglycemia typically present with **sweating**, pallor, and a normal or constricted pupil size. *Domperidone overdose* - **Domperidone** is a dopamine receptor antagonist and would generally cause **extrapyramidal symptoms**, hyperprolactinemia, or QT prolongation, not the anticholinergic syndrome observed. - An overdose would likely lead to symptoms such as **dystonia**, **akathisia**, or sedation, which are distinct from the patient's presentation. *Diabetic ketoacidosis* - **Diabetic ketoacidosis (DKA)** typically presents with severe hyperglycemia, metabolic acidosis, fruity breath, and deep, rapid breathing (**Kussmaul respirations**). - While confusion can occur, the lack of respiratory distress, the presence of markedly dilated pupils, and dry skin are not typical for DKA. *Heatstroke* - While **hyperthermia** and altered mental status are features of heatstroke, the presence of dilated pupils and agitation is also characteristic of anticholinergic toxicity. - The specific history of scopolamine ingestion makes anticholinergic overdose a more probable and direct cause than primary heatstroke, especially given the rapid onset after drug intake.

Question 31: A 56-year-old man presents seeking treatment for his baldness. He says he has noticed a bald patch in the center of his head which has increased in size over the past year. Physical examination and diagnostic tests show no evidence of an infectious cause. The patient is prescribed a drug be taken daily. After 4 months, the patient returns for follow-up and says that his hair growth has increased significantly. He denies any significant side effects except for a slight decrease in his sex drive. Which of the following is most likely the mechanism of action of the drug this patient was prescribed?

A. GnRH analog
B. Androgen receptor activation
C. Androgen receptor blocker
D. α1 adrenergic antagonist
E. 5α reductase inhibitor (Correct Answer)

Explanation: ***5α reductase inhibitor*** - The patient's presentation of male pattern baldness (androgenic alopecia) and improved hair growth with a **decreased sex drive** strongly suggests the use of a 5α-reductase inhibitor, such as **finasteride**. - These drugs inhibit the conversion of **testosterone to dihydrotestosterone (DHT)**, which is the primary androgen responsible for hair follicle miniaturization in androgenic alopecia, while the decreased DHT can lead to reduced libido. *GnRH analog* - **GnRH analogs** initially stimulate and then suppress the release of LH and FSH, leading to a significant reduction in sex hormone levels, which would likely cause more severe side effects like hot flashes and more pronounced sexual dysfunction. - While they can reduce androgen levels, they are typically used for conditions like prostate cancer or precocious puberty, not primarily for male pattern baldness due to their profound systemic effects. *Androgen receptor activation* - **Androgen receptor activation** would exacerbate male pattern baldness, as DHT acts by binding to these receptors in hair follicles. - Drugs that activate androgen receptors, such as exogenous testosterone, typically lead to increased hair loss on the scalp and other androgenic effects. *Androgen receptor blocker* - **Androgen receptor blockers** (e.g., spironolactone) can reduce hair loss in women but are less commonly used in men for male pattern baldness due to feminizing side effects and broader anti-androgenic effects beyond just DHT. - While they reduce the effect of androgens, the specific side effect profile and clinical use for male pattern baldness do not align as perfectly as a 5α-reductase inhibitor. *α1 adrenergic antagonist* - **α1 adrenergic antagonists** (e.g., tamsulosin) are primarily used to treat benign prostatic hyperplasia (BPH) or hypertension by relaxing smooth muscle. - These drugs have no direct role in hair growth or the mechanism of androgenetic alopecia and do not typically cause a decrease in sex drive as a primary or common side effect in this context.

Question 32: A 43-year-old woman is brought to the emergency department 10 minutes after the sudden onset of shortness of breath, dry cough, nausea, and an itchy rash. The symptoms started 15 minutes after she had dinner with her husband and her two sons at a local seafood restaurant. The patient has a 2-year history of hypertension treated with enalapril. She also uses an albuterol inhaler as needed for exercise-induced asthma. Empiric treatment with her inhaler has not notably improved her current symptoms. She has smoked one pack of cigarettes daily for the last 20 years. She drinks one to two glasses of wine every other day. She has never used illicit drugs. She appears uncomfortable and anxious. Her pulse is 124/min, respirations are 22/min and slightly labored, and blood pressure is 82/68 mm Hg. Examination of the skin shows erythematous patches and wheals over her trunk, back, upper arms, and thighs. Her lips appear slightly swollen. Expiratory wheezing is heard throughout both lung fields. The remainder of the physical examination shows no abnormalities. Which of the following is the most appropriate next step in the management of this patient?

A. Intravenous diphenhydramine and ranitidine administration
B. Intravenous methylprednisolone administration
C. Endotracheal intubation
D. Nebulized albuterol administration
E. Intramuscular epinephrine administration (Correct Answer)

Explanation: ***Intramuscular epinephrine administration*** - The patient presents with classic signs of **anaphylaxis**, including **acute onset**, **skin manifestations (hives, angioedema)**, **respiratory distress (shortness of breath, wheezing)**, and **hypotension (BP 82/68 mmHg)**, all following a potential allergen exposure (seafood). - **Epinephrine** is the **first-line treatment** for anaphylaxis due to its **alpha-1 adrenergic effects** (vasoconstriction, increasing blood pressure and reducing angioedema) and **beta-2 adrenergic effects** (bronchodilation, improving respiratory symptoms). *Intravenous diphenhydramine and ranitidine administration* - While **antihistamines (H1 blockers like diphenhydramine and H2 blockers like ranitidine)** can help alleviate cutaneous symptoms like itching and urticaria in anaphylaxis, they are **second-line agents** and do not address the life-threatening respiratory or cardiovascular compromise. - Relying solely on antihistamines in a hypotensive patient with respiratory distress would delay definitive treatment and risk clinical deterioration. *Intravenous methylprednisolone administration* - **Corticosteroids** like methylprednisolone are useful in anaphylaxis to prevent **biphasic reactions** and reduce prolonged inflammation, but their onset of action is **slow** (hours) and they are **not effective** for immediate life-threatening symptoms. - They should be administered after epinephrine and other immediate supportive measures are in place. *Endotracheal intubation* - **Endotracheal intubation** is a major invasive procedure for airway management and is considered when there is **imminent airway obstruction** or **refractory respiratory failure**. - While the patient has respiratory distress, the initial management for anaphylaxis-related airway compromise involves epinephrine, which can rapidly improve bronchospasm and laryngeal edema, potentially averting the need for intubation. *Nebulized albuterol administration* - **Nebulized albuterol** is a **beta-2 agonist** that can relieve bronchospasm and is appropriate for asthma exacerbations or isolated bronchoconstriction. - However, in anaphylaxis, the respiratory symptoms are just one component of a multi-system reaction that includes cardiovascular collapse and widespread vasodilation, which albuterol alone cannot address. Epinephrine is preferred as it has both **beta-2 and alpha-1 agonist** effects.

Question 33: An investigator is studying physiological changes in the autonomic nervous system in response to different stimuli. 40 μg of epinephrine is infused in a healthy volunteer over a period of 5 minutes, and phenoxybenzamine is subsequently administered. Which of the following effects is most likely to be observed in this volunteer?

A. Increased secretion of insulin
B. Increased pressure inside the bladder
C. Decreased breakdown of muscle glycogen
D. Decreased secretion of aqueous humor (Correct Answer)
E. Increased peripheral vascular resistance

Explanation: ***Decreased secretion of aqueous humor*** - Epinephrine activates **beta-2 adrenergic receptors** in the ciliary epithelium, which **reduces aqueous humor production**. - After phenoxybenzamine (an irreversible **alpha-blocker**) is administered, the **beta-receptor effects persist** because phenoxybenzamine only blocks alpha receptors. - Therefore, the beta-2 mediated reduction in aqueous humor secretion continues, making this the correct answer. *Increased secretion of insulin* - Epinephrine **inhibits insulin secretion** via alpha-2 receptor activation on pancreatic beta cells. - Even after alpha-blockade with phenoxybenzamine, beta-2 receptor activation can still suppress insulin release. - Insulin secretion would remain decreased or normal, not increased. *Increased pressure inside the bladder* - Epinephrine causes **beta-2 mediated relaxation** of the detrusor muscle (bladder wall). - After phenoxybenzamine blocks alpha-1 receptors at the internal sphincter, the beta-2 relaxation effects persist. - This would **decrease bladder pressure**, not increase it. *Decreased breakdown of muscle glycogen* - Epinephrine strongly stimulates **beta-2 receptors** in skeletal muscle, promoting **glycogenolysis** (breakdown of glycogen). - After alpha-blockade, beta receptor activation continues, so glycogen breakdown remains **increased**, not decreased. *Increased peripheral vascular resistance* - Initially, epinephrine causes alpha-1 mediated vasoconstriction and increased peripheral resistance. - However, after **phenoxybenzamine blocks alpha receptors**, only beta-2 effects remain. - Beta-2 activation causes **vasodilation** in skeletal muscle vessels, leading to **decreased peripheral vascular resistance** (this is the classic "epinephrine reversal" phenomenon). - Therefore, peripheral resistance would be **decreased**, not increased.

Question 34: A 30-year-old woman presents to an urgent care center with progressively worsening cough and difficulty breathing. She has had similar prior episodes since childhood, one of which required intubation with mechanical ventilation. On physical exam, she appears anxious and diaphoretic, with diffuse wheezes and diminished breath sounds bilaterally. First-line treatment for this patient’s symptoms acts by which of the following mechanisms of action?

A. Beta-2 antagonist
B. Beta-1 agonist
C. Beta-2 agonist (Correct Answer)
D. Beta-1 antagonist
E. Beta-3 agonist

Explanation: ***Beta-2 agonist*** - The patient's presentation with **worsening cough**, **difficulty breathing**, **diffuse wheezes**, and a history of similar episodes since childhood requiring intubation is highly suggestive of an **acute asthma exacerbation**. - **Short-acting beta-2 agonists (SABAs)** like albuterol are the **first-line treatment** for acute asthma symptoms, as they cause rapid **bronchodilation** by stimulating **beta-2 receptors** on airway smooth muscle. *Beta-2 antagonist* - A **beta-2 antagonist** would cause **bronchoconstriction**, exacerbating the patient's respiratory distress rather than relieving it. - This class of drugs is generally contraindicated in patients with asthma unless used with extreme caution and for specific indications like glaucoma, where topical beta-blockers might be used. *Beta-1 agonist* - **Beta-1 agonists** primarily affect the **heart**, increasing **heart rate** and **contractility**. - While they might have some minor beta-2 effects at higher doses, their primary action is not bronchodilation and they would be associated with significant unwanted cardiac side effects in this setting. *Beta-1 antagonist* - **Beta-1 antagonists** (beta-blockers) primarily act on the **heart** to decrease heart rate and contractility and would have no beneficial effect on bronchoconstriction. - Non-selective beta-blockers can even cause **bronchoconstriction** by blocking beta-2 receptors, making them potentially harmful in asthma. *Beta-3 agonist* - **Beta-3 agonists** are primarily involved in **lipolysis** and **bladder relaxation**. - They are used for conditions like overactive bladder but have no significant role in the treatment of acute asthma exacerbations.

Question 35: A 47-year-old woman comes to the physician because of repetitive tongue twisting and abnormal movements of the hands and legs that started several days ago. She has a 2-year history of schizophrenia that has been controlled with fluphenazine. Two weeks ago, she was switched to risperidone. Examination shows protrusion of the tongue and smacking of the lips. She makes twisting movements of the arms and frequently taps her right foot. Which of the following is the most likely diagnosis?

A. Acute dystonia
B. Akathisia
C. Tardive dyskinesia (Correct Answer)
D. Neuroleptic malignant syndrome
E. Cerebellar stroke

Explanation: ***Tardive dyskinesia*** - This condition involves **involuntary, repetitive movements** such as **tongue twisting, lip smacking, and abnormal movements of the hands and legs**, which are classic symptoms described. - It typically occurs after **prolonged use of dopamine receptor-blocking agents** (antipsychotics), usually requiring **months to years of exposure**. This patient had been on fluphenazine for 2 years. - The **switch from fluphenazine to risperidone** may have **unmasked or exacerbated** pre-existing tardive dyskinesia, as changes in antipsychotic regimens can alter the balance of dopamine blockade. *Acute dystonia* - Characterized by **sudden, sustained muscle contractions** causing abnormal postures, often affecting the neck, eyes (oculogyric crisis), or trunk. - Typically occurs within **hours to days** of initiating or increasing antipsychotic medication. - While timing could fit, the **repetitive, choreiform nature of the movements** (rather than sustained muscle contractions) makes tardive dyskinesia more likely. *Akathisia* - Presents as a subjective feeling of **inner restlessness** and an objective compulsion to move, such as frequently shifting weight, pacing, or inability to sit still. - Although the patient taps her foot, the predominant symptoms are **involuntary orofacial and limb movements** without described subjective restlessness, which are not typical of akathisia. *Neuroleptic malignant syndrome* - A life-threatening reaction characterized by a **tetrad of symptoms**: high fever, severe muscle rigidity ("lead-pipe" rigidity), autonomic instability (tachycardia, labile blood pressure, diaphoresis), and altered mental status. - The patient's presentation lacks these severe systemic signs and is instead focused on involuntary hyperkinetic movements. *Cerebellar stroke* - A stroke affecting the cerebellum would primarily cause **ataxia, nystagmus, dysarthria, and problems with coordination and balance**. - The described symptoms are primarily **involuntary hyperkinetic movements** related to chronic dopamine pathway dysfunction from antipsychotic use, not acute cerebellar pathology.

Question 36: A 30-year-old man presents with fatigue and low energy. He says that he has been "feeling down" and tired on most days for the last 3 years. He also says that he has had difficulty concentrating and has been sleeping excessively. The patient denies any manic or hypomanic symptoms. He also denies any suicidal ideation or preoccupation with death. A physical examination is unremarkable. Laboratory findings are significant for the following: Serum glucose (fasting) 88 mg/dL Serum electrolytes Sodium 142 mEq/L; Potassium: 3.9 mEq/L; Chloride: 101 mEq/L Serum creatinine 0.8 mg/dL Blood urea nitrogen 10 mg/dL Hemoglobin (Hb %) 15 g/dL Mean corpuscular volume (MCV) 85 fl Reticulocyte count 1% Erythrocyte count 5.1 million/mm3 Thyroid-stimulating hormone 3.5 μU/mL Medication is prescribed to this patient that increases norepinephrine neurotransmission. After 2 weeks, the patient returns for follow-up and complains of dizziness, dry mouth, and constipation. Which of the following drugs was most likely prescribed to this patient?

A. Clonidine
B. Lithium
C. Paroxetine
D. Venlafaxine (Correct Answer)
E. Phenylephrine

Explanation: ***Venlafaxine*** - This patient likely suffers from **persistent depressive disorder (dysthymia)** given the chronic fatigue, low energy, and depressed mood for over 2 years without manic/hypomanic episodes. - **Venlafaxine** is a **serotonin-norepinephrine reuptake inhibitor (SNRI)** that increases both serotonin and norepinephrine levels by blocking their reuptake at nerve terminals, thereby enhancing norepinephrine neurotransmission. - Common side effects include **dizziness, dry mouth, and constipation** due to anticholinergic effects and increased noradrenergic activity. *Clonidine* - **Clonidine** is an **alpha-2 adrenergic agonist** that reduces sympathetic outflow by activating presynaptic alpha-2 receptors, effectively decreasing norepinephrine release, which is contrary to the question's premise of increasing norepinephrine neurotransmission. - It is primarily used to treat **hypertension** and **ADHD**, and its side effects can include sedation and dry mouth, but it would not be prescribed to enhance norepinephrine activity. *Lithium* - **Lithium** is a mood stabilizer primarily used in the treatment of **bipolar disorder** and is not typically prescribed as a standalone antidepressant to increase norepinephrine neurotransmission. - Its side effects include **tremor, polyuria, polydipsia, and thyroid dysfunction**, which do not match the described side effect profile. *Paroxetine* - **Paroxetine** is a **selective serotonin reuptake inhibitor (SSRI)**, primarily increasing serotonin levels. It does not significantly increase norepinephrine neurotransmission. - While it can cause side effects like **dry mouth and constipation**, it would not fit the description of a drug that increases norepinephrine neurotransmission. *Phenylephrine* - **Phenylephrine** is an **alpha-1 adrenergic agonist** used as a decongestant or to increase blood pressure by directly stimulating postsynaptic alpha-1 receptors rather than enhancing neurotransmission through reuptake inhibition. - It would not be used to treat depression, and its side effects include **hypertension and reflex bradycardia**, which are not reported in the patient.

Question 37: A 25-year-old man is admitted to the hospital with acute onset dyspnea, chest pain, and fainting. The medical history is significant for infective endocarditis at the age of 17 years, and intravenous drug abuse prior to the disease. He reports a history of mild dyspnea on exertion. Currently, his only medication is duloxetine, which the patient takes for his depression. The vital signs include: blood pressure 160/100 mm Hg, heart rate 103/min, respiratory rate 21/min, temperature 38.1℃ (100.9℉), and oxygen saturation is 91% on room air. On physical examination, the patient is dyspneic, restless, confused, and anxious. His pupils are dilated, symmetrical, and reactive to light. The patient's skin is pale with acrocyanosis and clear without signs of injection. There is bilateral jugular venous distention. On lung auscultation, there are bilateral crackles at the lower lobes. Cardiac auscultation shows presence of an S3 gallop, an accentuated S2 best heard at the tricuspid and pulmonary areas, and a pansystolic grade 2/6 murmur over the tricuspid area. Abdominal examination is significant for enlarged liver palpated 3 cm below the costal margin. The complete blood count is only significant for decreased hemoglobin. His rapid HIV test is negative. Which of the following is the most likely cause of the condition of this patient?

A. Coronary atherosclerosis
B. Cocaine toxicity (Correct Answer)
C. Sepsis
D. Acute viral hepatitis
E. Duloxetine overdose

Explanation: **Cocaine toxicity** - This patient's acute symptoms, including **dyspnea**, **chest pain**, **tachycardia**, **hypertension**, **dilated pupils**, and **altered mental status (restlessness, confusion, anxiety)**, are highly consistent with acute **cocaine toxicity**. - Cocaine use can precipitate acute cardiac events like **myocardial ischemia** or **tachyarrhythmias**, leading to cardiogenic shock, and can also cause **pulmonary edema** from sympathetic overstimulation and direct cardiotoxicity, explaining the crackles and jugular venous distention. *Coronary atherosclerosis* - While coronary atherosclerosis can cause acute chest pain and dyspnea, it is less likely in a **25-year-old** without significant risk factors other than a history of intravenous drug abuse, which is a stronger risk factor for conditions like endocarditis or acute stimulant-induced cardiac events. - The prominent neurological symptoms like **dilated pupils**, **confusion**, and **anxiety** point strongly towards a stimulant-induced cause rather than primary atherosclerosis. *Sepsis* - Although the patient has a fever (38.1°C), tachycardia, and altered mental status, common in sepsis, the presence of **hypertension (160/100 mmHg)** and **dilated pupils** makes sepsis less likely as the primary cause. Sepsis typically presents with **hypotension** and sometimes constricted pupils in opioid-related cases. - The distinct cardiac findings, such as an **accentuated S2** and new **pansystolic murmur** (suggesting tricuspid regurgitation, possibly exacerbated by right heart strain), are not typical initial presentations of sepsis. *Acute viral hepatitis* - Acute viral hepatitis primarily affects the liver, causing symptoms like **jaundice**, **fatigue**, **nausea**, and **abdominal pain**. - It does not typically cause acute onset **dyspnea**, **chest pain**, **hypertension**, **tachycardia**, **dilated pupils**, or **pulmonary crackles** as the prominent features described in this patient. *Duloxetine overdose* - Duloxetine is a serotonin-norepinephrine reuptake inhibitor. Overdose can cause symptoms like **tachycardia**, **hypertension**, and **dilated pupils**, which overlap with the patient's presentation. - However, the severity of the **pulmonary edema** (bilateral crackles, dyspnea, low SpO2) and the **acute onset chest pain**, coupled with a history of intravenous drug abuse, make **cocaine toxicity** a more compelling diagnosis given its widely recognized acute cardiotoxicity.

Question 38: A 68-year-old man presents with urinary retention for the past week. He says his symptoms onset gradually almost immediately after being prescribed a new medication for his depression. He states that he has increased his fluid intake to try to help the issue, but this has been ineffective. He also mentions that he has been having problems with constipation and dry mouth. His past medical history is significant for major depressive disorder, diagnosed 6 months ago. The patient denies any history of smoking, alcohol consumption, or recreational drug use. He is afebrile, and his vital signs are within normal limits. A physical examination is unremarkable. A urinalysis is normal. Which of the following medications was this patient most likely prescribed for his depression?

A. Amitriptyline (Correct Answer)
B. Phenelzine
C. Mirtazapine
D. Citalopram
E. Venlafaxine

Explanation: **Amitriptyline** - This patient's symptoms of **urinary retention**, **dry mouth**, and **constipation** are classic **anticholinergic side effects** commonly associated with tricyclic antidepressants (TCAs) like amitriptyline. - The gradual onset and immediate appearance after starting a new antidepressant strongly point to an anticholinergic mechanism. - TCAs block muscarinic receptors, leading to decreased parasympathetic activity and these characteristic symptoms. *Phenelzine* - Phenelzine is a **monoamine oxidase inhibitor (MAOI)**. While effective for depression, it is generally associated with side effects such as **orthostatic hypotension**, **insomnia**, and **hypertensive crisis** with certain food interactions, not primarily anticholinergic effects like urinary retention. - Urinary retention is not a common or prominent side effect of MAOIs. *Mirtazapine* - Mirtazapine is an **alpha-2 adrenergic antagonist (NaSSA)** that primarily causes side effects like **sedation**, **increased appetite**, and **weight gain**. - While it has some antihistaminergic activity, it is less likely to cause severe anticholinergic effects such as urinary retention compared to TCAs. *Citalopram* - Citalopram is a **selective serotonin reuptake inhibitor (SSRI)**. Common side effects include **gastrointestinal upset**, **sexual dysfunction**, and **insomnia**. - SSRIs generally have a very low incidence of anticholinergic side effects; urinary retention is rare. *Venlafaxine* - Venlafaxine is a **serotonin-norepinephrine reuptake inhibitor (SNRI)**. Its common side effects include **nausea**, **dizziness**, **insomnia**, and **hypertension**. - Like SSRIs, SNRIs have minimal anticholinergic activity, making urinary retention an unlikely primary side effect.

Question 39: A 36-year-old woman with schizophrenia comes to the office for a follow-up appointment. She has been hospitalized 4 times in the past year, and she has failed to respond to multiple trials of antipsychotic medications. Six weeks ago, she was brought to the emergency department by her husband because of a bizarre behavior, paranoid delusions, and hearing voices that others did not hear. She was started on a new medication, and her symptoms have improved. Laboratory studies show: Hemoglobin 13.8 g/dL Leukocyte count 1,200/mm3 Segmented neutrophils 6% Eosinophils 0% Lymphocytes 92% Monocytes 2% Platelet count 245,000/mm3 This patient was most likely started on which of the following medications?

A. Clozapine (Correct Answer)
B. Promethazine
C. Fluphenazine
D. Lithium
E. Quetiapine

Explanation: ***Clozapine*** - The patient's presentation of **treatment-resistant schizophrenia** (failure to respond to multiple antipsychotics and recurrent hospitalizations) strongly points to clozapine as the most likely effective treatment. - The abnormal lab results, particularly **leukopenia** (total WBC 1,200/mm³) and severe **neutropenia** (segmented neutrophils 6%, absolute neutrophil count ~72/mm³), are a known and serious side effect of clozapine, requiring careful monitoring. *Promethazine* - Promethazine is an **antihistamine** with antiemetic and sedative properties, not a primary antipsychotic for schizophrenia. - It would not be used for chronic management of severe, treatment-resistant schizophrenia and is not associated with the severe hematological side effects seen here. *Fluphenazine* - Fluphenazine is a **first-generation antipsychotic** that could be used for schizophrenia, but the patient's history indicates failure of multiple antipsychotic trials. - While it can cause some side effects, severe leukopenia and neutropenia to the degree seen here are not characteristic of fluphenazine. *Lithium* - Lithium is a **mood stabilizer** primarily used for bipolar disorder, not typical first-line or even second-line treatment for schizophrenia as a monotherapy. - Notably, lithium typically causes **leukocytosis** (increased WBC count), not leukopenia, making it inconsistent with the lab findings showing severe leukopenia and neutropenia. *Quetiapine* - Quetiapine is a **second-generation antipsychotic** that is used for schizophrenia, but it is less effective for treatment-resistant cases compared to clozapine. - While some antipsychotics can cause mild hematologic changes, quetiapine is not known for causing the profound leukopenia and severe neutropenia seen in this patient, which are distinctly associated with clozapine.

Question 40: A 25-year-old woman presents to an urgent care center following a presumed bee sting while at a picnic with her friends. She immediately developed a skin rash and swelling over her arms and face. She endorses diffuse itching over her torso. She denies any episodes similar to this and has no significant medical history. She does note that her father has an allergy to peanuts. Her blood pressure is 92/54 mm Hg, heart rate, 118/min, respiratory rate 18/min. On physical examination, the patient has severe edema over her face and inspiratory stridor. Of the following options, this patient is likely experiencing which of the following hypersensitivity reactions?

A. Type 2 hypersensitivity reaction
B. Type 1 hypersensitivity reaction (Correct Answer)
C. Type 3 hypersensitivity reaction
D. Mixed type 1 and type 3 hypersensitivity reactions
E. Type 4 hypersensitivity reaction

Explanation: ***Type 1 hypersensitivity reaction*** - This patient is experiencing **anaphylaxis**, which is a severe, systemic manifestation of a **Type 1 hypersensitivity reaction**. Key features include rapid onset, exposure to an allergen (bee sting), **skin rash**, **angioedema** (facial edema, swelling over arms), diffuse itching, **hypotension**, **tachycardia**, and **inspiratory stridor** (indicating airway obstruction). - **Type 1 hypersensitivity** is mediated by **IgE antibodies** binding to mast cells and basophils, leading to the rapid release of histamine and other inflammatory mediators upon re-exposure to the allergen. *Type 2 hypersensitivity reaction* - **Type 2 hypersensitivity** involves **IgG** or **IgM antibodies** binding directly to antigens on the surface of target cells, leading to cell destruction, dysfunction, or damage. - Examples include **hemolytic transfusion reactions** or **autoimmune hemolytic anemia**, which do not match the presented symptoms. *Type 3 hypersensitivity reaction* - **Type 3 hypersensitivity** is characterized by the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues, leading to inflammation and tissue damage. - Conditions like **serum sickness** or **lupus nephritis** are examples, typically having a delayed onset and different clinical presentation than an acute allergic reaction. *Mixed type 1 and type 3 hypersensitivity reactions* - While some conditions can involve multiple types of hypersensitivity reactions, the acute, immediate, and systemic nature of this patient's symptoms are overwhelmingly consistent with a **pure Type 1 IgE-mediated anaphylactic response**. - There is no clinical evidence presented (e.g., vasculitis, glomerulonephritis) to suggest an accompanying **Type 3 reaction** in this acute setting. *Type 4 hypersensitivity reaction* - **Type 4 hypersensitivity** is a **delayed-type hypersensitivity (DTH)** reaction mediated by **T cells** rather than antibodies. - Symptoms typically develop much later (24-72 hours) after exposure, as seen in **contact dermatitis** (e.g., poison ivy) or the **tuberculin skin test**, which is inconsistent with the immediate onset of this patient's symptoms.

Question 41: A 67-year-old man presents to the emergency room with malaise, nausea, and vomiting. Four hours prior to presentation, he was spraying insecticide at his farm when he started feeling nauseous. He has had multiple episodes of diarrhea and has vomited non-bloody, non-bilious fluid twice. He also complains of muscle cramps and tremors. His past medical history is notable for hypertension, diabetes, hyperlipidemia, and a prior myocardial infarction. He takes aspirin, metoprolol, metformin, lisinopril, and atorvastatin. He has a 40-pack-year smoking history and drinks 3-4 shots of whiskey per day. His temperature is 98.6°F (37°C), blood pressure is 148/88 mmHg, pulse is 96/min, and respirations are 22/min. He is alert and oriented to person and place but not to time. He is diaphoretic and tremulous. His pupils are 2 mm bilaterally. The patient's clothing is removed, and he is placed in a medical gown. Which of the following is the most appropriate initial treatment for this patient?

A. Naloxone
B. Activated charcoal
C. Physostigmine
D. Atropine (Correct Answer)
E. Pralidoxime

Explanation: ***Atropine*** - The patient's symptoms (malaise, nausea, vomiting, diarrhea, muscle cramps, tremors, diaphoresis, constricted pupils) after insecticide exposure are classic for **organophosphate poisoning**. - **Atropine** is the **first-line initial treatment** as it rapidly reverses life-threatening **muscarinic effects** including bronchospasm, bronchorrhea, bradycardia, and excessive secretions. - Atropine competitively blocks muscarinic acetylcholine receptors, counteracting the excess acetylcholine that accumulates due to acetylcholinesterase inhibition. - It should be given in **large doses** (2-5 mg IV initially, repeated every 5-10 minutes) until signs of atropinization appear (dry mouth, mydriasis, tachycardia). *Naloxone* - **Naloxone** is an opioid antagonist used to reverse opioid overdose. - The patient's symptoms are inconsistent with opioid intoxication, which typically causes **respiratory depression** and **miosis** but not the widespread cholinergic effects (diarrhea, diaphoresis, muscle fasciculations) seen here. *Activated charcoal* - **Activated charcoal** can be used as a gastrointestinal decontaminant in some poisonings to adsorb toxins and prevent absorption. - However, for organophosphate poisoning, prompt administration of **atropine** is the priority due to the rapid onset and life-threatening nature of muscarinic symptoms. - Activated charcoal may have limited utility as organophosphates are often absorbed dermally or via inhalation. *Physostigmine* - **Physostigmine** is an acetylcholinesterase inhibitor used to treat anticholinergic toxicity. - Giving physostigmine in a case of organophosphate poisoning (which already involves excess acetylcholine) would dangerously **exacerbate cholinergic symptoms** and could be fatal. *Pralidoxime* - **Pralidoxime** reactivates **acetylcholinesterase** by cleaving the phosphate-enzyme bond, reversing both muscarinic and nicotinic effects. - While pralidoxime is an important **adjunctive treatment** for organophosphate poisoning, it is given **after atropine** has been administered. - Pralidoxime is most effective when given within 24-48 hours of exposure and primarily reverses **nicotinic effects** (muscle weakness, fasciculations, respiratory muscle paralysis).

Question 42: A 32-year-old man presents with difficulty sleeping and ‘feeling low’ for the past 6 months. Although he denies any suicidal thoughts, he admits to having an occasional feeling of hopelessness and loss of concentration at work. For the last 2 months, he has made excuses to avoid meeting his friends. He got married 1 year ago. The couple plans to try to have a child. He was started on sertraline 3 months ago and says it has not helped his depressive symptoms. He says he has also developed erectile dysfunction since starting the medication, which has been an issue since he and his wife would like to have a child. Past medical history is insignificant. The patient is afebrile and vital signs are within normal limits. Physical examination is unremarkable. Laboratory studies, including thyroid-stimulating hormone (TSH), are within normal limits. When switching drugs, which of the following would be most appropriate for this patient?

A. Nortriptyline
B. Fluoxetine
C. Bupropion (Correct Answer)
D. Buspirone
E. Phenelzine

Explanation: ***Bupropion*** - This patient is experiencing **sexual dysfunction** with sertraline, and bupropion is a good choice because it has a **lower incidence of sexual side effects** compared to SSRIs. - Bupropion works as a **norepinephrine-dopamine reuptake inhibitor (NDRI)**, which can be activating and helpful for symptoms like low energy and concentration issues. *Nortriptyline* - Nortriptyline is a **tricyclic antidepressant (TCA)** that can have significant anticholinergic side effects (e.g., dry mouth, constipation, urinary retention) and may cause **cardiac conduction abnormalities** in susceptible individuals. - While it might be an option, its side effect profile is generally less favorable than bupropion in a patient seeking to avoid sexual dysfunction and minimize side effects. *Fluoxetine* - Fluoxetine is another **selective serotonin reuptake inhibitor (SSRI)**, similar to sertraline, and is also associated with a high incidence of **sexual side effects**, which is precisely what the patient is trying to avoid. - Switching from one SSRI to another when sexual dysfunction is the primary concern is unlikely to resolve the issue. *Buspirone* - Buspirone is an **anxiolytic** that primarily acts on serotonin receptors, but it is **not a primary antidepressant** for moderate to severe depression. - It might be used as an adjunct for anxiety symptoms, but it would not be appropriate as a monotherapy switch for persistent depressive symptoms. *Phenelzine* - Phenelzine is a **monoamine oxidase inhibitor (MAOI)**, typically reserved for **treatment-resistant depression** due to its significant dietary restrictions (tyramine-free diet) and potential for **hypertensive crisis**. - Given that the patient has only tried one SSRI, an MAOI would be an overly aggressive and high-risk choice at this stage.

Question 43: A 61-year-old man decides to undergo surgery for a hip replacement after seeing no improvement in his pain with non-operative treatment. At some point during the surgery, he is administered an agent that results in fasciculations in the patient's extremities. This was the expected response to the administered agent so no intervention was needed. After a while, the fasciculations stop and remain stopped for the remainder of the surgery. Consider the period of time during which the patient had fasciculations and subsequently the period of time after the fasciculations stopped. If the effects of the administered agent needed to be reversed during each of these two time periods respectively, which of the following agents should be administered during each time period?

A. Neostigmine, no reversal
B. No reversal, neostigmine (Correct Answer)
C. No reversal, atracurium
D. Atracurium, atracurium
E. Neostigmine, neostigmine

Explanation: ***No reversal, neostigmine*** - The agent causing **fasciculations** is **succinylcholine**, a **depolarizing neuromuscular blocker** - During the **Phase I block** (fasciculation phase), succinylcholine actively stimulates **nicotinic acetylcholine receptors**, causing depolarization - Administering **neostigmine** (an acetylcholinesterase inhibitor) during Phase I would **worsen the block** by increasing acetylcholine concentration and prolonging depolarization - After fasciculations stop, continuous exposure leads to **Phase II block** with **receptor desensitization**, mimicking a non-depolarizing block - During Phase II, **neostigmine** can reverse the block by increasing acetylcholine at the neuromuscular junction, allowing competition with succinylcholine at desensitized receptors *Neostigmine, no reversal* - Administering **neostigmine** during Phase I would exacerbate the depolarizing block by preventing acetylcholine breakdown - Stating "no reversal" for Phase II is incorrect, as Phase II block can often be partially or fully reversed with neostigmine *No reversal, atracurium* - While "no reversal" is correct for the Phase I block, **atracurium** is not a reversal agent - **Atracurium** is a non-depolarizing neuromuscular blocker that would further potentiate the blockade by blocking acetylcholine receptors *Atracurium, atracurium* - **Atracurium** is a neuromuscular blocking agent, not a reversal agent - It would worsen paralysis rather than reverse it in either phase of succinylcholine block *Neostigmine, neostigmine* - Administering **neostigmine** during Phase I would dangerously prolong depolarization and worsen the block - While neostigmine is appropriate for Phase II block reversal, its use in Phase I makes this option incorrect

Question 44: A 70-year-old man with a history of Alzheimer dementia presents to the emergency department with a change in his behavior. The patient has been more confused recently and had a fever. Upon presentation, he is too confused to answer questions. His temperature is 103°F (39.4°C), blood pressure is 102/68 mmHg, pulse is 157/min, respirations are 22/min, and oxygen saturation is 99% on room air. The patient is given 3 liters of IV fluids and acetaminophen and his vitals improve. He is also less confused. The patient is asking where he is and becomes combative and strikes a nurse when he finds out he has to be admitted to the hospital. He is given diphenhydramine for sedation and put in soft restraints. His mental status subsequently worsens and he becomes much more aggressive, spitting at nurses and attempting to bite his restraints. He also complains of abdominal pain. A post void residual volume is notable for a urine volume of 750 mL. Which of the following is the etiology of this patient's recent mental status change?

A. Diphenhydramine (Correct Answer)
B. Lorazepam
C. Haloperidol
D. Acute infection
E. Olanzapine

Explanation: ***Diphenhydramine*** - This patient exhibited a **paradoxical reaction** (increased agitation and aggression) to diphenhydramine, which is an **anticholinergic** medication. - Anticholinergic drugs can worsen confusion and agitation, especially in elderly patients or those with pre-existing **dementia**. *Lorazepam* - **Benzodiazepines** like lorazepam primarily work on **GABA receptors** to produce sedative and anxiolytic effects. - While sometimes used for agitation, it typically causes sedation rather than increased aggression in the elderly; a paradoxical reaction is less common than with anticholinergics. *Haloperidol* - Haloperidol is a **first-generation antipsychotic** used to treat acute agitation and psychosis, primarily by blocking **dopamine D2 receptors**. - Its typical effect would be to decrease agitation and aggression, not worsen mental status in this manner. *Acute infection* - The patient initially presented with signs of an acute infection (fever, increased confusion), which improved after initial treatment with IV fluids and acetaminophen, indicating the initial symptoms were likely due to infection. - The subsequent worsening after diphenhydramine points to a new etiology for the mental status change, rather than a resurgence of the infection. *Olanzapine* - Olanzapine is a **second-generation antipsychotic** that blocks serotonin and dopamine receptors, often used for acute agitation. - Like haloperidol, it would be expected to reduce agitation and aggression, not exacerbate it, and was not administered to the patient according to the vignette.

Question 45: A 78-year-old man suffers a fall in a nursing home and is brought to the emergency room. A right hip fracture is diagnosed, and he is treated with a closed reduction with internal fixation under spinal anesthesia. On the second postoperative day, the patient complains of pain in the lower abdomen and states that he has not urinated since the surgery. An ultrasound shows increased bladder size and volume. Which of the following is the mechanism of action of the drug which is most commonly used to treat this patient’s condition?

A. Alpha-blocker
B. Parasympathetic antagonist
C. Sympathetic agonist
D. Beta-blocker
E. Parasympathetic agonist (Correct Answer)

Explanation: ***Parasympathetic agonist*** - The patient presents with **postoperative urinary retention (POUR)**, commonly treated with **bethanechol**, a muscarinic cholinergic agonist. - Bethanechol acts as a **parasympathetic agonist**, stimulating **muscarinic receptors** on the **detrusor muscle** of the bladder, causing it to contract and facilitating urination. *Alpha-blocker* - **Alpha-blockers** (e.g., tamsulosin) relax the **smooth muscle** of the prostatic urethra and bladder neck, often used for **benign prostatic hyperplasia (BPH)**. - While they can improve urinary flow, they do not directly stimulate **detrusor contraction** and are not the primary treatment for acute POUR. *Parasympathetic antagonist* - **Parasympathetic antagonists** (e.g., oxybutynin) block muscarinic receptors, leading to **detrusor relaxation**. - These drugs are used to treat conditions like **overactive bladder** or **urge incontinence**, which involve excessive bladder contraction, and would worsen urinary retention. *Sympathetic agonist* - **Sympathetic agonists** (e.g., norepinephrine) primarily cause vasoconstriction and cardiac stimulation. - They tend to **relax the detrusor muscle** and contract the internal urethral sphincter via **beta-3 and alpha-1 receptors**, respectively, which would exacerbate urinary retention. *Beta-blocker* - **Beta-blockers** (e.g., propranolol) primarily affect the heart and blood vessels, slowing heart rate and lowering blood pressure. - They have **no direct primary role** in the treatment of acute urinary retention as they do not directly act on bladder contractility.

Question 46: A 49-year-old man presents to his primary care physician complaining of multiple symptoms. He states that over the past 8 months he has noticed voice changes and difficulty swallowing. The dysphagia started with just dry foods like crackers but has progressed to include smoothies and ice cream. He works as a newspaper editor and has also noticed trouble writing with his dominant hand. He is accompanied by his wife, who complains that he snores and drools in his sleep. His medical history is significant for hypertension and a bicuspid aortic valve. He takes hydrochlorothiazide. On physical examination, there is atrophy of the right hand. The patient’s speech is slow. A systolic murmur at the right upper sternal border is appreciated. Tapping of the left patellar tendon causes the patient’s left lower extremity to forcefully kick out. Stroking of the plantar aspect of the patient’s left foot causes his left toes to extend upward. Which of the following therapies is most likely to slow the progression of the patient’s symptoms?

A. Amantadine
B. Beta interferon
C. Riluzole (Correct Answer)
D. Donepezil
E. Reserpine

Explanation: ***Riluzole*** - This patient presents with symptoms highly suggestive of **amyotrophic lateral sclerosis (ALS)**, including progressive **dysphagia**, **voice changes**, **hand weakness/atrophy**, **hyperreflexia** (forceful patellar reflex), and a **positive Babinski sign** (extension of toes). **Riluzole** is the only medication shown to slightly prolong survival and slow the progression of ALS by inhibiting glutamate release. - The patient's **snores and drools** are also consistent with bulbar involvement seen in ALS, as is the progressive dysphagia from dry foods to liquids. *Amantadine* - **Amantadine** is an antiviral drug primarily used to treat **influenza A** and to alleviate **dyskinesia** associated with **Parkinson's disease**. - It has no known efficacy in slowing the progression of **ALS**. *Beta interferon* - **Beta interferon** is a medication used to treat **multiple sclerosis (MS)** by modulating the immune system to reduce inflammation and neuron damage. - While MS can cause neurological symptoms, the clinical picture here with both upper and lower motor neuron signs without clear sensory deficits or relapsing-remitting course is not typical for MS, and beta interferon is not effective for **ALS**. *Donepezil* - **Donepezil** is a **cholinesterase inhibitor** primarily used to treat the symptoms of **Alzheimer's disease** by increasing acetylcholine levels in the brain, improving cognitive function. - It does not address the motor neuron degeneration characteristic of **ALS**. *Reserpine* - **Reserpine** is an **antihypertensive and antipsychotic** drug that depletes catecholamines and serotonin from nerve endings. - It is used to treat conditions like **hypertension and dyskinesias** (e.g., in Huntington's disease) but has no role in the management or slowing of **ALS** progression.

Question 47: A 79-year-old man, hospitalized for overnight monitoring after elective surgery, is found on morning rounds to be confused and disoriented. He was recovering well in the post-anesthesia care unit before being moved up to the inpatient floor unit; however, he was found to be delirious and agitated overnight. Therefore, he was given a dose of a drug that affects the opening frequency of a neuronal ion channel. During morning rounds, he is found to have weakness, tremors, uncoordinated muscle movements, blurred vision, and disorientation. Which of the following could be used to reverse the drug that was administered to this patient?

A. Flumazenil (Correct Answer)
B. Activated charcoal
C. Naloxone
D. Ammonium chloride
E. Sodium bicarbonate

Explanation: ***Flumazenil*** - The patient exhibits symptoms of **benzodiazepine overdose**, likely from medication given for agitation, which include confusion, disorientation, weakness, and uncoordinated movements. - **Flumazenil** is a selective competitive antagonist of the **GABA-A receptor**, effectively reversing the effects of benzodiazepines. *Activated charcoal* - **Activated charcoal** is used for drug overdose by **adsorbing toxins** in the gastrointestinal tract, preventing systemic absorption. - It is not an antidote for central nervous system depressant toxicities once the drug has already been absorbed and exerted its effects, and it is most effective when administered shortly after ingestion. *Naloxone* - **Naloxone** is an opioid receptor antagonist used to reverse the effects of **opioid overdose**, primarily respiratory depression. - The patient's symptoms are inconsistent with opioid overdose, which would typically present with pinpoint pupils and respiratory depression rather than the described neurological and motor deficits. *Ammonium chloride* - **Ammonium chloride** is used to **acidify urine** to increase the excretion of basic drugs. - It does not directly reverse the central nervous system effects of an overdose and is not a specific antidote for benzodiazepine toxicity. *Sodium bicarbonate* - **Sodium bicarbonate** is used to **alkalinize urine** to promote the excretion of acidic drugs, or to treat metabolic acidosis or certain drug toxicities like tricyclic antidepressants. - It would not reverse the direct neurological effects of a benzodiazepine overdose.

Question 48: A 9-year-old boy is brought to the physician by his mother because of poor performance in school for the last year. He has difficulty sitting still at his desk, does not follow the teacher's instructions, and frequently blurts out answers in class. He often gets sent outside the classroom for failing to work quietly. At hockey practice, he does not wait his turn and has difficulty listening to his coach's instructions. His mother reports that he is easily distracted when she speaks with him and that he often forgets his books at home. Physical examination shows no abnormalities. Which of the following is the most appropriate pharmacotherapy?

A. Varenicline
B. Fluoxetine
C. Suvorexant
D. Atomoxetine (Correct Answer)
E. Risperidone

Explanation: ***Atomoxetine*** - The patient's symptoms of inattention, hyperactivity, and impulsivity are highly suggestive of **Attention-Deficit/Hyperactivity Disorder (ADHD)**. Atomoxetine is a **non-stimulant medication** that is FDA-approved for the treatment of ADHD in children, adolescents, and adults. - It works by selectively inhibiting the **norepinephrine transporter**, increasing norepinephrine levels in the prefrontal cortex, which helps improve attention and reduce impulsivity. *Varenicline* - **Varenicline** is a medication primarily used for **smoking cessation**, acting as a partial agonist at nicotinic acetylcholine receptors. - It has no established role in the treatment of ADHD and would not address the patient's symptoms. *Fluoxetine* - **Fluoxetine** is a **selective serotonin reuptake inhibitor (SSRI)** commonly used to treat depression, anxiety disorders, and obsessive-compulsive disorder. - While co-occurring anxiety or depression can happen with ADHD, the primary symptoms presented in the case are classic for ADHD, not primarily mood or anxiety disorders. *Suvorexant* - **Suvorexant** is an **orexin receptor antagonist** used for the treatment of insomnia, by blocking the wake-promoting effects of orexin. - It is not indicated for ADHD and would not improve the patient's inattention or hyperactivity. *Risperidone* - **Risperidone** is an **atypical antipsychotic** used to treat conditions like schizophrenia, bipolar disorder, and irritability associated with autism. - While it can be used for severe behavioral problems, it is not a first-line treatment for ADHD and would carry more significant side effects than ADHD-specific medications.

Question 49: An 18-year-old boy presents to the clinic with shortness of breath and fever for the last 2 days. He also has a cough for the same duration. He is asthmatic and uses inhaled albuterol for symptom relief when required. He used albuterol today 3 times at 10-minute intervals but has not had relief of his symptoms. On physical examination, his temperature is 38.3°C (101.0°F), pulse is 130/min, blood pressure is 116/80 mm Hg, and respirations are 28/min. Auscultation of the chest reveals bilateral crackles. Considering that he has already taken inhaled albuterol and has tachycardia, the physician nebulizes him with inhaled ipratropium bromide, which significantly improves his symptoms. Which of the following is the mechanism of action of this drug?

A. Inhibition of vagally-mediated contraction of bronchial smooth muscles (Correct Answer)
B. Inhibition of degranulation of mast cells
C. Inhibition of phosphodiesterase-4, leading to prevention of release of cytokines and chemokines
D. Inhibition of adenosine receptors in the respiratory tract
E. Stimulation of β2-adrenergic receptors in bronchial smooth muscle

Explanation: ***Inhibition of vagally-mediated contraction of bronchial smooth muscles*** - Ipratropium bromide is a **short-acting muscarinic antagonist (SAMA)** that blocks M3 muscarinic receptors on bronchial smooth muscle - This action **inhibits acetylcholine's effect**, leading to bronchodilation by preventing vagally-mediated bronchoconstriction - Particularly useful as an **adjunct to β2-agonists** in acute asthma exacerbations and COPD *Inhibition of degranulation of mast cells* - This is the mechanism of action of **mast cell stabilizers** like cromolyn sodium and nedocromil - These drugs are used for **asthma prophylaxis**, not acute symptom relief - They prevent the release of inflammatory mediators like histamine from mast cells *Inhibition of phosphodiesterase-4, leading to prevention of release of cytokines and chemokines* - This is the mechanism of action of **phosphodiesterase-4 (PDE4) inhibitors** such as roflumilast - Primarily used in **severe COPD** to reduce inflammation - PDE4 inhibition increases intracellular cAMP, which has anti-inflammatory effects *Inhibition of adenosine receptors in the respiratory tract* - This is the mechanism of action of **methylxanthines** like theophylline and aminophylline - Blocking adenosine receptors provides bronchodilation and reduces inflammation - Now considered **second-line therapy** due to narrow therapeutic index *Stimulation of β2-adrenergic receptors in bronchial smooth muscle* - This is the mechanism of action of **β2-agonists** like albuterol (already used by this patient) - Not the mechanism of ipratropium, which is an **anticholinergic** agent - The patient had already received albuterol without adequate relief, prompting the addition of ipratropium

Question 50: A 59-year-old man comes to the physician because of a 1-year history of increased urinary frequency, weak urinary stream, and occasional straining to void urine. Rectal examination shows a large, nontender prostate without asymmetry or nodularity. His serum creatinine, prostate-specific antigen, and urinalysis are all within the reference range. A diagnosis of benign prostatic hyperplasia is made, and treatment with tamsulosin is begun. Which of the following changes in intracellular messaging is most likely to occur in response to this drug?

A. Decreased activity of phospholipase C (Correct Answer)
B. Increased activity of protein kinase C
C. Increased production of diacylglycerol
D. Decreased activity of protein kinase A
E. Increased activity of adenylyl cyclase

Explanation: ***Decreased activity of phospholipase C*** - **Tamsulosin** is an **alpha-1 adrenergic receptor antagonist** that works by blocking alpha-1 receptors on the smooth muscle of the prostate and bladder neck, causing relaxation. - Alpha-1 receptor activation normally utilizes the **Gq protein pathway**, which leads to the activation of phospholipase C, thus blocking these receptors decreases phospholipase C activity. *Increased activity of protein kinase C* - **Protein kinase C** is activated by **diacylglycerol (DAG)** and intracellular calcium, both of which are products of the phospholipase C pathway. - Since tamsulosin decreases phospholipase C activity, it would subsequently lead to a *decrease*, not an increase, in protein kinase C activity. *Increased production of diacylglycerol* - **Diacylglycerol (DAG)** is a secondary messenger produced by the action of **phospholipase C** on **phosphatidylinositol bisphosphate (PIP2)**. - As tamsulosin inhibits the alpha-1 receptor and thus phospholipase C activity, it would *decrease* the production of DAG. *Decreased activity of protein kinase A* - **Protein kinase A (PKA)** is typically activated by **cyclic AMP (cAMP)**, which is produced by **adenylyl cyclase**. - The alpha-1 receptor pathway (affected by tamsulosin) primarily involves phospholipase C, not adenylyl cyclase or protein kinase A. *Increased activity of adenylyl cyclase* - **Adenylyl cyclase** is responsible for converting **ATP to cAMP**, which is part of the Gs protein signaling pathway (beta-adrenergic receptors) or Gi protein pathway (alpha-2 adrenergic receptors). - Tamsulosin specifically targets **alpha-1 adrenergic receptors** which are coupled to **Gq proteins**, not Gs or Gi proteins; therefore, it does not directly affect adenylyl cyclase activity.

Question 51: A 16-year-old college student presents to the emergency department with a 3-day history of fever, muscle rigidity, and confusion. He was started on a new medication for schizophrenia 2 months ago. There is no history of sore throat, burning micturition, or loose motions. At the hospital, his temperature is 38.6°C (101.5°F); the blood pressure is 108/62 mm Hg; the pulse is 120/min, and the respiratory rate is 16/min. His urine is cola-colored. On physical examination, he is sweating profusely. Treatment is started with antipyretics and intravenous hydration. Which of the following is most likely responsible for this patient's condition?

A. Diazepam
B. Phenytoin
C. Levodopa
D. Amantadine
E. Chlorpromazine (Correct Answer)

Explanation: ***Chlorpromazine*** - The patient's symptoms of **fever**, **muscle rigidity**, and **confusion**, combined with a history of starting an antipsychotic medication (**Chlorpromazine**), are highly indicative of **neuroleptic malignant syndrome (NMS)**. - **Chlorpromazine** is a typical antipsychotic known to block dopamine receptors, which can lead to NMS. The **cola-colored urine** suggests **rhabdomyolysis**, a common complication of severe muscle rigidity in NMS. *Diazepam* - **Diazepam** is a benzodiazepine used to treat anxiety, seizures, and muscle spasms, and does not typically cause NMS. - Its mechanism of action involves enhancing GABAergic neurotransmission, which is distinct from the dopaminergic blockade associated with NMS. *Phenytoin* - **Phenytoin** is an anticonvulsant medication that can cause a variety of side effects, but NMS is not one of them. - Common side effects include **gingival hyperplasia**, **ataxia**, and **nystagmus**. *Levodopa* - **Levodopa** is primarily used to treat Parkinson's disease by increasing dopamine levels in the brain. - While abrupt withdrawal of **Levodopa** can sometimes precipitate NMS-like symptoms in Parkinson's patients due to inadequate dopamine, starting it does not cause NMS, and it is not typically used for schizophrenia. *Amantadine* - **Amantadine** is an antiviral drug also used to treat Parkinson's disease; it is not an antipsychotic. - It primarily acts as a dopamine agonist and NMDA receptor antagonist, and its use is not associated with causing NMS.

Question 52: A 56-year-old man presents with constipation and trouble urinating for the past day. He says that he tried drinking a lot of water but that did not help. He also says that he has been tired all the time recently. Past medical history is significant for schizophrenia, diagnosed 3 months ago, and being managed on chlorpromazine. Current medications also include sildenafil. The vital signs include blood pressure 80/45 mm Hg, respiratory rate 23/min, heart rate 86/min and temperature 38.7°C (101.7°F). On physical examination, the patient appears agitated and confused. Which of the following medications is the most likely cause of this patient's presentation?

A. Chlorpromazine (Correct Answer)
B. Ziprasidone
C. Haloperidol
D. Aripiprazole
E. Lithium

Explanation: ***Chlorpromazine*** - The patient's presentation with **constipation**, **trouble urinating**, **fever**, **tachycardia**, **hypotension**, **agitation**, and **confusion** is highly suggestive of **anticholinergic toxicity**. - **Chlorpromazine**, a low-potency first-generation antipsychotic, has significant **anticholinergic side effects** due to its potent blockade of muscarinic receptors, making it the most likely cause. *Ziprasidone* - Ziprasidone is a **second-generation antipsychotic** known for a lower propensity for anticholinergic side effects compared to first-generation agents like chlorpromazine. - While it can cause side effects, severe anticholinergic toxicity is less common and less pronounced with ziprasidone. *Haloperidol* - Haloperidol is a **high-potency first-generation antipsychotic** with relatively weak anticholinergic properties compared to chlorpromazine. - It is more commonly associated with **extrapyramidal symptoms** rather than the severe anticholinergic syndrome described. *Aripiprazole* - Aripiprazole is a **second-generation antipsychotic** with **dopamine partial agonist** properties and very low anticholinergic activity. - It would be an unlikely cause of the profound anticholinergic toxicity observed in this patient. *Lithium* - Lithium is a **mood stabilizer** used in bipolar disorder and does not possess significant anticholinergic properties. - Lithium toxicity typically presents with **tremor**, **nausea**, **vomiting**, **diarrhea**, and **neurological symptoms** like ataxia, rather than the specific constellation of anticholinergic symptoms seen here.

Question 53: A 55-year-old man is brought to the emergency department 3 hours after ingesting approximately 30 tablets of an unknown drug in an apparent suicide attempt. His temperature is 36.5°C (97.7°F), pulse is 40/min, respiratory rate is 19/min, and blood pressure is 85/50 mm Hg. Examination shows cold, clammy extremities. Scattered expiratory wheezing is heard throughout both lung fields. His fingerstick blood glucose concentration is 62 mg/dL. ECG shows prolonged PR intervals and narrow QRS complexes. Intravenous fluid resuscitation and atropine do not improve his symptoms. Administration of which of the following drugs is most appropriate next step in management of this patient?

A. Activated charcoal
B. Sodium bicarbonate
C. Naloxone
D. Glucagon (Correct Answer)
E. Pralidoxime

Explanation: ***Glucagon*** - This patient presents with **bradycardia**, **hypotension**, **hypoglycemia**, **bronchospasm** (expiratory wheezing), and **prolonged PR intervals** after ingesting an unknown drug. These symptoms are classic for **beta-blocker overdose**. - **Glucagon** is indicated in severe beta-blocker overdose when conventional therapies like atropine and IV fluids are ineffective, as it increases cAMP independent of the beta-adrenergic receptor. *Activated charcoal* - While generally useful for recent ingestions to prevent absorption, its utility significantly decreases **3 hours post-ingestion**, especially as the drug may have already been absorbed. - Furthermore, this patient is exhibiting **severe clinical toxicity**, requiring specific antidotal treatment rather than just decontamination. *Sodium bicarbonate* - **Sodium bicarbonate** is primarily used in cases of **tricyclic antidepressant (TCA) overdose** to treat QRS widening and metabolic acidosis. - It is not indicated for beta-blocker overdose, as the ECG shows prolonged PR intervals with narrow QRS complexes, not QRS widening. *Naloxone* - **Naloxone** is the antidote for **opioid overdose**, characterized by respiratory depression, miosis, and sedation. - This patient's symptoms (bradycardia, hypotension, bronchospasm, prolonged PR interval) are not consistent with opioid toxicity. *Pralidoxime* - **Pralidoxime** is an antidote for **organophosphate poisoning**, acting as a cholinesterase reactivator. - Organophosphate poisoning presents with cholinergic symptoms (e.g., salivation, lacrimation, urination, defecation, bronchospasm, miosis), but also tachycardia, not the profound bradycardia seen here.

Question 54: A 59-year-old male presents to his primary care physician complaining of a tremor. He developed a tremor in his left hand approximately three months ago. It appears to be worse at rest and diminishes if he points to something or uses the hand to hold an object. His past medical history is notable for emphysema and myasthenia gravis. He has a 40 pack-year smoking history. Physical examination reveals slowed movements. The patient takes several seconds to rise from his chair for a gait analysis which reveals a shuffling gait. The physician decides to start the patient on a medication that prevents the degradation of a neurotransmitter. This medication is also indicated for use in which of the following conditions?

A. Hyperprolactinemia
B. Seasonal allergies
C. Influenza
D. Major depressive disorder (Correct Answer)
E. Restless leg syndrome

Explanation: ***Major depressive disorder*** - The patient's symptoms (resting tremor worse at rest, bradykinesia, shuffling gait) are classic for **Parkinson's disease**, caused by dopamine deficiency in the substantia nigra - The medication that **prevents neurotransmitter degradation** refers to **MAO-B inhibitors** (e.g., selegiline, rasagiline), which inhibit monoamine oxidase type B, preventing the breakdown of dopamine - **MAO inhibitors** as a class prevent the degradation of monoamine neurotransmitters (dopamine, norepinephrine, serotonin) - **Non-selective MAO inhibitors** (phenelzine, tranylcypromine) and **MAO-A inhibitors** (moclobemide) are used to treat **major depressive disorder**, particularly treatment-resistant depression - Both MAO-B inhibitors (for Parkinson's) and MAO-A inhibitors (for depression) work by preventing enzymatic degradation of neurotransmitters *Hyperprolactinemia* - Treated with **dopamine agonists** (bromocriptine, cabergoline) that directly stimulate dopamine D2 receptors to suppress prolactin secretion - These are not degradation inhibitors but receptor agonists *Seasonal allergies* - Treated with antihistamines, nasal corticosteroids, or leukotriene inhibitors - No role for medications that prevent neurotransmitter degradation *Influenza* - Treated with antiviral medications (oseltamivir, zanamivir) that inhibit neuraminidase - Note: While oseltamivir inhibits viral neuraminidase (an enzyme), this is unrelated to neurotransmitter degradation in the CNS *Restless leg syndrome* - Primarily treated with **dopamine agonists** (pramipexole, ropinirole) that stimulate dopamine receptors - While dopamine is involved, the mechanism is receptor stimulation, not prevention of degradation

Question 55: Pancreatic islets were isolated from a healthy, non-diabetic donor to perform an experiment to look at insulin secretion inhibition. Compounds would be added to separate wells containing the islets bathed in a high glucose solution for one hour. After one hour, the supernatant would be collected, and the insulin content would be measured with an enzyme-linked immunosorbent assay (ELISA). Which of the following compounds would result in the least insulin secretion when added to the islets?

A. Isoproterenol
B. Dobutamine
C. Glyburide
D. Tolbutamide
E. Clonidine (Correct Answer)

Explanation: ***Clonidine*** - Clonidine is an **alpha-2 adrenergic agonist**, which acts to inhibit insulin secretion from pancreatic beta cells. Alpha-2 receptors, when activated, reduce intracellular cAMP levels, thereby **suppressing insulin release**. - In a high glucose environment, this inhibitory action of clonidine would result in the **least insulin secretion** compared to other listed compounds which either stimulate insulin secretion or have less direct inhibitory effects. *Isoproterenol* - Isoproterenol is a **non-selective beta-adrenergic agonist** (β1 and β2). Activation of beta-adrenergic receptors on pancreatic beta cells generally **stimulates insulin secretion** by increasing intracellular cAMP. - Therefore, adding isoproterenol would lead to **increased insulin release**, not decreased. *Dobutamine* - Dobutamine is primarily a **beta-1 adrenergic agonist**, though it has some beta-2 effects. Beta-1 activation on pancreatic cells is not the primary mechanism associated with insulin regulation. - While it may have some minor impact, its main action is on cardiac contractility and it is **not known to significantly inhibit insulin secretion** from beta cells. *Glyburide* - Glyburide is a **sulfonylurea drug** that works by binding to the SUR1 subunit of the **ATP-sensitive potassium (KATP) channel** on pancreatic beta cells, thereby closing it. - This closure leads to **depolarization of the cell membrane**, calcium influx, and ultimately **increased insulin secretion**. *Tolbutamide* - Tolbutamide is another **sulfonylurea drug**, similar to glyburide, that acts by binding to and blocking the **ATP-sensitive potassium (KATP) channels** on pancreatic beta cells. - This mechanism leads to beta cell depolarization, **calcium entry**, and **stimulation of insulin release**.

Question 56: A 29-year-old female visits her gynecologist because of an inability to conceive with her husband. Past medical history reveals that she has been amenorrheic for several months, and she complains of frequent white nipple discharge. Urine tests for beta-HCG are negative. A receptor agonist for which of the following would be most likely to treat her condition:

A. Dopamine (Correct Answer)
B. Somatostatin
C. Insulin
D. Vasopressin
E. Serotonin

Explanation: ***Dopamine*** - The patient's symptoms of **amenorrhea**, difficulty conceiving, and **galactorrhea** (white nipple discharge) in a non-pregnant state are classic for **hyperprolactinemia**. - **Dopamine agonists** like cabergoline or bromocriptine are the first-line treatment as dopamine inhibits prolactin release from the anterior pituitary. *Somatostatin* - **Somatostatin** inhibits the release of various hormones, including **growth hormone** and **TSH**, but does not directly or primarily regulate prolactin in a therapeutic context for hyperprolactinemia. - While somatostatin analogs can be used for neuroendocrine tumors that secrete other hormones, they are **not the treatment of choice** for simple hyperprolactinemia. *Insulin* - **Insulin** is a hormone involved in **glucose metabolism** and has no direct role in the regulation of prolactin or the treatment of hyperprolactinemia. - Its primary therapeutic use is in the management of **diabetes mellitus**. *Vasopressin* - **Vasopressin** (ADH) regulates **water reabsorption** in the kidneys and affects blood pressure. - It is **not involved** in the regulation of prolactin secretion or the management of galactorrhea/amenorrhea. *Serotonin* - **Serotonin** typically has a **stimulatory effect** on prolactin release, meaning agonists would worsen hyperprolactinemia, whereas antagonists might decrease it. - Therefore, a receptor agonist for serotonin would be **contraindicated** and not a treatment for this condition.

Question 57: A 35-year-old woman comes to the physician because of blurred vision for the past 2 months. During this period, she has also had difficulty chewing and swallowing. She reports that her symptoms worsen throughout the day and improve with rest. There is no personal or family history of serious illness. The patient works as a teacher and has had a great deal of stress lately. She does not smoke and drinks a glass of wine occasionally. She takes no medications. Her temperature is 37°C (98.6°F), pulse is 68/min, and blood pressure is 130/80 mm Hg. Physical examination shows bilateral ptosis and mask-like facies. Muscle strength is decreased in both lower extremities. The anti–acetylcholine receptor (AChR) antibody test is positive. Electromyography shows a decremental response following repetitive nerve stimulation. Which of the following is the most appropriate next step in the management of this patient?

A. Serum ACTH and CRH levels
B. Plasmapheresis
C. Anti-VGCC antibody level
D. Physostigmine therapy
E. CT scan of the chest (Correct Answer)

Explanation: ***CT scan of the chest*** - The patient has symptoms suggestive of **myasthenia gravis**, including **ptosis**, **diplopia** (blurred vision), **dysphagia**, and **fatigue that worsens with activity and improves with rest**. The positive **anti-acetylcholine receptor (AChR) antibody** test and **decremental response on EMG** confirm the diagnosis. A computed tomography (CT) scan of the chest is crucial to evaluate for a **thymoma**, which is present in 10-15% of patients with myasthenia gravis and can be surgically resected, potentially leading to symptom improvement or remission. - Approximately 85% of myasthenia gravis patients have detectable **AChR antibodies**, making this test highly specific for the condition. The presence of these antibodies, along with the characteristic clinical picture and electromyography findings, establishes the diagnosis of myasthenia gravis. Thymectomy is often considered in patients with generalized myasthenia gravis, even in the absence of a thymoma, due to potential therapeutic benefits. *Serum ACTH and CRH levels* - This test is primarily used to investigate conditions related to the **hypothalamic-pituitary-adrenal axis**, such as **Cushing's disease** or **Addison's disease**. - There are no symptoms presented that would suggest altered ACTH or CRH levels, making this an inappropriate diagnostic step for the current patient's presentation. *Plasmapheresis* - **Plasmapheresis** is a treatment for **acute severe myasthenia gravis** or **myasthenic crisis**, involving the removal of plasma to eliminate circulating antibodies. - While it is a treatment for myasthenia gravis, it is not the *next step* in initial workup after diagnosis for a stable patient as described; the priority is to investigate underlying causes like thymoma. *Anti-VGCC antibody level* - **Anti-voltage-gated calcium channel (VGCC) antibodies** are characteristic of **Lambert-Eaton Myasthenic Syndrome (LEMS)**, often associated with **small cell lung cancer**. - The patient's symptoms (e.g., ptosis, worsening with activity) and the positive **AChR antibodies** are classic for myasthenia gravis, not LEMS, making this test unnecessary. *Physostigmine therapy* - **Physostigmine** is an **acetylcholinesterase inhibitor** that reverses anticholinergic effects and can be used in some contexts, but it's not a primary treatment for myasthenia gravis. - The standard pharmacotherapy for myasthenia gravis includes other anticholinesterase inhibitors like **pyridostigmine**, or immunomodulatory agents. This is a treatment, not a diagnostic step in the workup.

Question 58: A 30-year-old man is brought to the emergency department by his brother for the evaluation of progressive confusion over the past 6 hours. The patient is lethargic and unable to answer questions. His brother states that there is no personal or family history of serious illness. His temperature is 37°C (98.6°F), pulse is 110/min, and blood pressure 135/80 mm Hg. Physical examination shows warm, dry skin and dry mucous membranes. The pupils are dilated. The abdomen is distended and bowel sounds are hypoactive. Laboratory studies are within normal limits. An ECG shows no abnormalities. Intoxication with which of the following substances is the most likely cause of this patient's symptoms?

A. Cannabis
B. Amphetamine
C. Opioid
D. Carbon monoxide
E. Antihistamine (Correct Answer)

Explanation: ***Antihistamine*** - The patient's symptoms, including **dilated pupils**, confusion, lethargy, dry skin and mucous membranes, distended abdomen, and hypoactive bowel sounds, are consistent with an **anticholinergic toxidrome**. This pattern is often seen with antihistamine overdose due to their anticholinergic properties. - The elevated pulse despite normal blood pressure and temperature also aligns with anticholinergic effects. *Cannabis* - Cannabis intoxication typically causes **conjunctival injection**, xerostomia, increased appetite, and impaired coordination. - While it can cause lethargy, it does not explain the dilated pupils, dry mucous membranes, or hypoactive bowel sounds. *Amphetamine* - Amphetamine intoxication usually presents with **tachycardia**, hypertension, agitation, paranoia, and diaphoresis, not dry skin or hypoactive bowel sounds. - Though pupils are typically dilated, the overall clinical picture points away from amphetamine overdose. *Opioid* - Opioid overdose is characterized by **respiratory depression**, **miosis (pinpoint pupils)**, and altered mental status, which contradict the dilated pupils and normal respiratory effort (implied by normal oxygenation and stable vital signs) in this case. - While it can cause lethargy and hypoactive bowel sounds, other key features are missing or are opposite. *Carbon monoxide* - Carbon monoxide poisoning classically presents with **headache**, nausea, vomiting, confusion, and sometimes the classic "**cherry-red skin**" (though this is rare and late). - It does not cause dilated pupils, dry mucous membranes, or hypoactive bowel sounds as seen in this patient.

Question 59: A 32-year-old farmer is brought to the emergency department by his wife. The patient was reportedly anxious, sweaty, and complaining of a headache and chest tightness before losing consciousness on route to the hospital. Which of the following is mechanistically responsible for this patient's symptoms?

A. Reversible inhibition of acetylcholinesterase
B. Competitive inhibition of acetylcholine at post-junctional effector sites
C. Binding of acetylcholine agonists to post-junctional receptors
D. Irreversible inhibition of acetylcholinesterase (Correct Answer)
E. Inhibition of presynaptic exocytosis of acetylcholine vesicles

Explanation: ***Irreversible inhibition of acetylcholinesterase*** - The farmer's symptoms (anxiety, sweating, headache, chest tightness, loss of consciousness) are characteristic of **organophosphate poisoning**, which causes a cholinergic crisis due to accumulation of acetylcholine. - Organophosphates are common in **pesticides** and act by irreversibly inhibiting **acetylcholinesterase**, leading to prolonged stimulation of cholinergic receptors. *Reversible inhibition of acetylcholinesterase* - Reversible acetylcholinesterase inhibitors, such as **physostigmine** or **neostigmine**, typically have a shorter duration of action and might cause similar symptoms but are less likely to lead to such severe, acute presentations in an accidental exposure scenario for a farmer. - These agents are often used therapeutically and would not typically cause prolonged loss of consciousness in this context unless in very high intentional doses. *Competitive inhibition of acetylcholine at post-junctional effector sites* - This mechanism describes the action of **anticholinergic drugs** (e.g., atropine), which would block acetylcholine's effects and cause symptoms like dry mouth, dilated pupils, and tachycardia, opposite to what is observed here. - Such agents would alleviate, not cause, the cholinergic symptoms seen in this patient. *Binding of acetylcholine agonists to post-junctional receptors* - While direct agonists (e.g., pilocarpine, methacholine) would mimic acetylcholine and cause cholinergic symptoms, organophosphate poisoning operates by preventing acetylcholine breakdown, rather than directly binding as an exogenous agonist. - The context of a farmer and sudden, severe symptoms points more strongly to pesticide exposure and acetylcholinesterase inhibition. *Inhibition of presynaptic exocytosis of acetylcholine vesicles* - This mechanism is characteristic of **botulinum toxin**, which blocks the release of acetylcholine from presynaptic terminals, leading to muscle paralysis and weakness. - The patient's symptoms are those of cholinergic excess, not cholinergic blockade or deficiency at the neuromuscular junction.

Question 60: A drug research team has synthesized a novel oral drug that acts as an agonist at multiple adrenergic receptors. When administered in animals, it has been shown to produce urinary retention at therapeutic doses with the absence of other manifestations of adrenergic stimulation. The researchers are interested in understanding signal transduction and molecular mechanisms behind the action of the novel drug. Which of the following receptors would most likely transduce signals across the plasma membrane following the administration of this novel drug?

A. GoPCRs (Go protein-coupled receptors)
B. GsPCRs (Gs protein-coupled receptors)
C. GqPCRs (Gq protein-coupled receptors) (Correct Answer)
D. GtPCRs (Gt protein-coupled receptors)
E. GiPCRs (Gi protein-coupled receptors)

Explanation: ***GqPCRs (Gq protein-coupled receptors)*** - **Urinary retention** is primarily mediated by the activation of **alpha-1 adrenergic receptors** in the bladder neck and prostate, which are classically Gq-protein coupled receptors. - Activation of **GqPCRs** leads to the activation of **phospholipase C**, increased **IP3 (inositol trisphosphate)** and **DAG (diacylglycerol)**, and subsequently, a rise in intracellular **calcium**, causing smooth muscle contraction. *GoPCRs (Go protein-coupled receptors)* - While Go proteins are a subtype of Gi/Go family, their direct primary role in mediating **urinary retention** via **adrenergic agonism** is not as well-established as Gq. - Go signaling often involves modulation of **ion channels** and can be involved in neuronal signaling, not directly causing smooth muscle contraction in the bladder. *GsPCRs (Gs protein-coupled receptors)* - **GsPCRs** (e.g., beta-adrenergic receptors) activate **adenylate cyclase**, leading to increased **cAMP** levels, which typically causes smooth muscle relaxation. - This effect would promote **urinary relaxation** and flow, not retention, and hence is contrary to the observed drug effect. *GtPCRs (Gt protein-coupled receptors)* - **GtPCRs** (transducin) are primarily involved in the **phototransduction** cascade in the retina, mediating vision. - They have no known central role in mediating adrenergic effects on the **urinary tract smooth muscle**. *GiPCRs (Gi protein-coupled receptors)* - **GiPCRs** (e.g., alpha-2 adrenergic receptors) inhibit **adenylate cyclase**, leading to decreased **cAMP** levels, which generally causes smooth muscle contraction in some tissues, but also presynaptic inhibition. - While Gi activation can lead to contraction in some contexts, the primary mechanism of **urinary retention** via bladder neck contraction is through alpha-1 receptors linked to Gq.

Question 61: A 20-year-old man visits the clinic for a regular follow-up appointment. Patient says he has been experiencing dry mouth and flushing of his skin for the past few days. He also feels tired and sleepy most of the time. Past medical history is significant for a skin rash a couple weeks ago after eating strawberries, for which he has prescribed a medication that he is still taking. Which of the following is the most likely etiology of this patient’s symptoms?

A. Inhibition of parasympathetic receptors (Correct Answer)
B. Inhibition of histamine receptors
C. Inhibition of alpha-1 adrenergic receptors
D. Activation of parasympathetic receptors
E. Activation of alpha-1 adrenergic receptors

Explanation: ***Inhibition of parasympathetic receptors*** - The patient's symptoms of **dry mouth**, **flushing**, **fatigue**, and **somnolence** are characteristic side effects of **anticholinergic** medications. - Many **first-generation antihistamines**, often prescribed for allergic reactions like the patient's rash, have significant **anticholinergic properties** due to their antagonism of **muscarinic acetylcholine receptors**. *Inhibition of histamine receptors* - While antihistamines **inhibit histamine receptors** (specifically H1 receptors), this action primarily leads to relief of allergic symptoms like rash, itching, and rhinorrhea. - The symptoms of dry mouth, flushing, and somnolence are not directly caused by H1 receptor blockade itself but rather by the **additional anticholinergic effects** of older antihistamines. *Inhibition of alpha-1 adrenergic receptors* - **Alpha-1 adrenergic receptor inhibition** typically causes **vasodilation**, which can lead to orthostatic hypotension, dizziness, and reflex tachycardia, but not explicitly dry mouth or significant flushing as described. - This mechanism is characteristic of medications like **alpha-blockers** used for hypertension or benign prostatic hyperplasia, not typically antihistamines. *Activation of parasympathetic receptors* - **Activation of parasympathetic receptors** (cholinergic effects) would produce symptoms opposite to those observed, such as increased salivation (not dry mouth), sweating, bradycardia, and miosis. - This effect is seen with **cholinergic agonists**, not with the antihistamines likely prescribed for an allergic rash. *Activation of alpha-1 adrenergic receptors* - **Activation of alpha-1 adrenergic receptors** leads to **vasoconstriction**, increased peripheral resistance, and mydriasis (pupil dilation). - This would cause symptoms like pallor and hypertension, which are contrary to the patient's reported flushing and fatigue.

Question 62: A 35-year-old man comes to the physician because of dull abdominal pain on his right side for 4 months. He also reports episodic nausea and vomiting during this period. He does not have fever, altered bowel habits, or weight loss. He has had a pet dog for 8 years. He appears healthy. Vital signs are within normal limits. Abdominal examination shows a nontender mass 3 cm below the right costal margin that moves with respiration. Laboratory studies show: Hemoglobin 14.6 g/dL Leukocyte count 7200/mm3 Segmented neutrophils 58% Eosinophils 8% Lymphocytes 30% Monocytes 4% Ultrasound of the abdomen shows a focal hypoechoic cyst within the liver measuring 7 cm. An ELISA confirms the diagnosis. He is scheduled for CT-guided percutaneous drainage under general anesthesia with orotracheal intubation. Seven minutes into the procedure, the patient's oxygen saturation suddenly decreases from 95% to 64%. His heart rate is 136/min, and blood pressure is 86/58 mm Hg. Examination shows diffuse expiratory wheezing bilaterally with poor air movement. Which of the following is most appropriate next step in management?

A. Cricothyrotomy
B. Exploratory laparotomy
C. Epinephrine (Correct Answer)
D. Chest tube insertion
E. Norepinephrine

Explanation: ***Epinephrine*** - The sudden onset of **hypoxemia**, **hypotension**, and **tachycardia** in a patient undergoing a procedure, especially one involving fluid aspiration from a parasitic cyst, strongly suggests **anaphylaxis** due to hypersensitivity to parasitic antigens. - **Epinephrine** is the first-line treatment for anaphylaxis due to its alpha-1 agonist effects (increasing blood pressure and decreasing mucosal edema) and beta-2 agonist effects (bronchodilation), which directly address the physiological collapse. *Cricothyrotomy* - This procedure is indicated for **upper airway obstruction** that cannot be managed by other means, such as failed intubation or severe laryngeal edema. - While the patient has respiratory compromise, the absent breath sounds and rapidly decreasing oxygen saturation suggest bronchospasm and systemic vasodilation, not primarily a mechanical upper airway obstruction amenable to cricothyrotomy. *Exploratory laparotomy* - This is a surgical procedure to investigate the abdominal cavity and is not indicated for an acute, life-threatening allergic reaction. - It would not address the patient's immediate respiratory or circulatory collapse. *Chest tube insertion* - **Chest tube insertion** is used to treat conditions like **pneumothorax** or **hemothorax**, which would typically present with unilateral absent breath sounds or other specific findings. - The bilateral absent breath sounds and rapidly declining systemic condition are more consistent with severe bronchospasm from anaphylaxis rather than a tension pneumothorax. *Norepinephrine* - **Norepinephrine** is a powerful vasopressor primarily used to treat **hypotension** in distributive shock. - While it can raise blood pressure, it lacks the critical bronchodilatory effects of epinephrine, which are essential in managing the severe bronchospasm seen in anaphylaxis.

Question 63: A 24-year-old woman presents to her primary care physician for bilateral nipple discharge. She states that this started recently and seems to be worsening. She denies any other current symptoms. The patient states that she is not currently sexually active, and her last menstrual period was over a month ago. Her medical history is notable for atopic dermatitis and a recent hospitalization for an episode of psychosis. Her temperature is 99.5°F (37.5°C), blood pressure is 110/65 mmHg, pulse is 70/min, respirations are 15/min, and oxygen saturation is 98% on room air. Cardiopulmonary and abdominal exam are within normal limits. Which of the following is the most likely cause of this patient's symptoms?

A. Prolactin-secreting mass
B. Alteration of the tuberoinfundibular pathway (Correct Answer)
C. Alteration of the nigrostriatal pathway
D. Normal pregnancy
E. Alteration of the mesolimbic pathway

Explanation: ***Alteration of the tuberoinfundibular pathway*** - Bilateral nipple discharge (galactorrhea) in this patient, especially after a recent hospitalization for psychosis, is highly suggestive of **hyperprolactinemia** caused by antipsychotic medication. Antipsychotics block dopamine D2 receptors in the **tuberoinfundibular pathway**, leading to increased prolactin secretion. - The patient's history of psychosis indicates she is likely on **antipsychotic medication**, which is a common cause of drug-induced hyperprolactinemia and galactorrhea. *Prolactin-secreting mass* - While a **prolactinoma** can cause galactorrhea, it typically presents with more pronounced symptoms (e.g., visual field defects, headaches, amenorrhea) and is a diagnosis of exclusion after ruling out more common causes like medication. - Given the **history of psychosis** and recent hospitalization, drug-induced hyperprolactinemia is a more immediate and likely explanation than a pituitary tumor. *Alteration of the nigrostriatal pathway* - Alteration of the **nigrostriatal pathway** is primarily associated with **extrapyramidal symptoms** (e.g., parkinsonism, dystonia, akathisia) due to dopamine receptor blockade by antipsychotics. - This pathway's dysfunction does not directly cause galactorrhea or hyperprolactinemia. *Normal pregnancy* - Although **pregnancy** causes galactorrhea due to elevated prolactin levels, the patient's statement of "not currently sexually active" and only a "last menstrual period was over a month ago" makes it less likely than drug-induced hyperprolactinemia given her medical history. - While a pregnancy test would be part of the workup, her current symptoms and medical history point more strongly to **medication-induced effects**. *Alteration of the mesolimbic pathway* - The **mesolimbic pathway** is primarily involved in reward, motivation, and psychosis; its hyperactivity is implicated in the positive symptoms of **schizophrenia**. - While antipsychotics target this pathway to reduce psychotic symptoms, its alteration per se does not directly cause galactorrhea.

Question 64: A 19-year-old man is brought to the emergency department by his mother because of increasing agitation and aggression at home. He has a history of bipolar disorder. During the last week, he has refused to take his lithium medication because it makes him “feel empty inside.” The mother thinks he has experimented with illicit drugs in the past. He appears acutely agitated, yells at multiple medical staff members, and demands to be discharged. His temperature is 37.7°C (99.8°F), pulse is 95/min, respirations are 18/min, and blood pressure is 140/75 mm Hg. Haloperidol is administered and the patient is admitted. The next morning, the patient reports worsening neck pain. He states that his neck is locked to the left and he cannot move it. Examination shows rigidity of his upper body and neck, with the neck fixed in flexion and rotated to the left. Administration of which of the following is the most appropriate next step in the management of this patient?

A. Bromocriptine
B. Physostigmine
C. Botulinum toxin
D. Benztropine (Correct Answer)
E. Diazepam

Explanation: ***Benztropine*** - The patient is experiencing an acute **dystonic reaction** due to haloperidol, presenting with severe neck rigidity, flexion, and rotation (torticollis). - **Benztropine**, an anticholinergic medication, is the first-line treatment for acute dystonia as it blocks muscarinic receptors and restores the **acetylcholine-dopamine balance**. *Bromocriptine* - This is a **dopamine agonist** typically used to treat **neuroleptic malignant syndrome (NMS)**, which presents with fever, severe muscle rigidity, autonomic instability, and altered mental status. - The patient's symptoms are more consistent with acute dystonia, not NMS, and his temperature is only mildly elevated. *Physostigmine* - This is an **acetylcholinesterase inhibitor** used to reverse anticholinergic toxicity, which would present with symptoms like dry mouth, blurred vision, delirium, and urinary retention. - The patient's symptoms of acute dystonia are caused by **dopamine blockade** leading to a **relative excess of cholinergic activity**, not anticholinergic poisoning. *Botulinum toxin* - While effective for chronic dystonia and muscle spasms, **botulinum toxin** is not the appropriate first-line treatment for an acute drug-induced dystonic reaction. - Its effects are not immediate, and it is usually reserved for cases refractory to oral medications or for focal dystonias. *Diazepam* - As a **benzodiazepine**, diazepam can provide some muscle relaxation and reduce anxiety, but it is not the primary treatment for reversing the neurochemical imbalance causing acute dystonia. - It could be used as an adjunct for agitation or muscle spasms, but an anticholinergic is directly indicated for dystonia.

Question 65: A previously healthy 25-year-old woman comes to the physician because of a 1-month history of palpitations that occur on minimal exertion and sometimes at rest. She has no chest discomfort or shortness of breath. She feels nervous and irritable most of the time and attributes these feelings to her boyfriend leaving her 2 months ago. Since then she has started exercising more frequently and taking an herbal weight-loss pill, since which she has lost 6.8 kg (15 lb) of weight. She finds it hard to fall asleep and awakens 1 hour before the alarm goes off each morning. She has been drinking 2 to 3 cups of coffee daily for the past 7 years and has smoked one pack of cigarettes daily for the past 3 years. Her temperature is 37.4°C (99.4°F), pulse is 110/min, respirations are 18/min, and blood pressure is 150/70 mm Hg. Examination shows moist palms. Neurologic examination shows a fine resting tremor of the hands. Deep tendon reflexes are 3+ with a shortened relaxation phase. Which of the following is the most likely cause of this patient's symptoms?

A. Exogenous hyperthyroidism (Correct Answer)
B. Pheochromocytoma
C. Hashimoto thyroiditis
D. Coffee consumption
E. Generalized anxiety disorder

Explanation: ***Exogenous hyperthyroidism*** - The patient's symptoms including **palpitations, weight loss, nervousness, irritability, insomnia**, and physical findings like **tachycardia, moist palms, fine tremor**, and **hyperreflexia with shortened relaxation phase** are highly indicative of **hyperthyroidism**. - The use of an **herbal weight-loss pill** strongly suggests the possibility of exogenous thyroid hormone intake or other thyroid-stimulating substances within the pill, leading to **exogenous hyperthyroidism**. *Pheochromocytoma* - While **palpitations** and **hypertension** can occur, **pheochromocytoma** is typically characterized by paroxysmal episodes of severe headaches, sweating, and anxiety. - The chronic nature of the patient's symptoms, along with significant **weight loss** and **hyperreflexia**, are less typical for **pheochromocytoma**. *Hashimoto thyroiditis* - **Hashimoto thyroiditis** typically causes **hypothyroidism**, characterized by symptoms like weight gain, fatigue, cold intolerance, and bradycardia. - While it can sometimes have a transient hyperthyroid phase (hashitoxicosis), the overall clinical picture here is more consistent with sustained **hyperthyroidism**, especially given the suspected external factor. *Coffee consumption* - Although **caffeine** can cause palpitations, nervousness, and insomnia, the severity and breadth of this patient's symptoms, including significant **weight loss, hyperreflexia**, and **moist palms**, extend far beyond what would typically be attributed solely to coffee intake, especially given her chronic coffee use. - The new onset and progression of these symptoms, coinciding with the herbal pill, points to a stronger underlying cause. *Generalized anxiety disorder* - **Generalized anxiety disorder (GAD)** can explain nervousness, irritability, and insomnia, but it does not typically cause **significant weight loss** or objective physical findings such as **tachycardia, moist palms, fine tremor, and hyperreflexia**. - These physical signs are hallmarks of a physiological rather than purely psychological condition.

Question 66: A 9-month-old baby boy is brought to his pediatrician due to poor feeding and fewer bowel movements. His father notes that he has been less active and is having difficulty with movements such as rolling over. Vital signs are normal, and physical exam is notable for weak sucking reflex, ptosis, and decreased eye movements. In addition, the baby has generalized weakness and flushed skin. Stool samples are collected, treatment is started immediately, and the baby’s condition improves. The results of the stool studies return several days later and show gram-positive, anaerobic rods. The toxin most likely responsible for this baby’s condition acts through which mechanism?

A. Impairment of phagocytosis
B. Increased chloride secretion within the gut
C. Inhibition of protein synthesis
D. Inhibition of neurotransmitter release (Correct Answer)
E. Degradation of the cell membrane

Explanation: ***Inhibition of neurotransmitter release*** - The baby's symptoms of **generalized weakness**, **weak sucking reflex**, **ptosis**, and **decreased eye movements** are characteristic of **infant botulism**, caused by *Clostridium botulinum* toxins. - These toxins, specifically the **botulinum neurotoxin**, block the release of **acetylcholine** at the **neuromuscular junction**, leading to flaccid paralysis. *Impairment of phagocytosis* - This mechanism is not directly related to the symptoms of **flaccid paralysis** seen in infant botulism. - Phagocytosis is primarily involved in immune responses and pathogen clearance, not nerve transmission. *Increased chloride secretion within the gut* - While some bacterial toxins, like **cholera toxin**, cause increased chloride secretion leading to watery diarrhea, this is not the mechanism of botulinum toxin. - The baby's symptoms point to neurological impairment, not excessive fluid loss in the gut. *Inhibition of protein synthesis* - Toxins such as **diphtheria toxin** or **Shiga toxin** inhibit protein synthesis, leading to cell death and specific clinical manifestations different from those presented here. - The symptoms described are due to a highly specific blockage of neurotransmission rather than general cellular dysfunction. *Degradation of the cell membrane* - This mechanism is characteristic of toxins that form **pores** or enzymes that directly **damage cell membranes**, leading to cell lysis. - Examples include alpha-toxin of *Clostridium perfringens*, but it does not align with the neurological symptoms of infant botulism.

Question 67: A 24-year-old man with a history of schizophrenia presents for follow-up. The patient says that he is still having paranoia and visual hallucinations on his latest atypical antipsychotic medication. Past medical history is significant for schizophrenia diagnosed 1 year ago that failed to be adequately controlled on 2 separate atypical antipsychotic medications. The patient is switched to a typical antipsychotic medication. Which of the following is the mechanism of action of the medication that was most likely prescribed for this patient?

A. Dopaminergic receptor antagonist (Correct Answer)
B. Dopaminergic partial agonist
C. Serotonergic receptor agonist
D. Serotonergic receptor antagonist
E. Cholinergic receptor agonist

Explanation: ***Dopaminergic receptor antagonist*** - The patient has **treatment-resistant schizophrenia**, indicated by failure to respond to two different atypical antipsychotics. - Typical antipsychotics like **haloperidol** or **fluphenazine** are primarily **D2 dopamine receptor antagonists**, which may be used when a patient has not responded to atypical agents. - The **primary mechanism** of typical (first-generation) antipsychotics is **potent D2 receptor blockade** in the mesolimbic pathway, which reduces positive symptoms of schizophrenia. - Note: Clozapine would be the preferred choice for true treatment-resistant schizophrenia, but typical antipsychotics may still be considered in some clinical scenarios. *Dopaminergic partial agonist* - **Dopamine partial agonists**, such as **aripiprazole** or **brexpiprazole**, are **atypical antipsychotics** used for schizophrenia. - The patient has failed to respond to atypical antipsychotics already, making it unlikely that another atypical agent would be the next choice. - The question specifically states the patient is switched to a **typical antipsychotic**. *Serotonergic receptor agonist* - **Serotonin receptor agonists**, like LSD or psilocybin, are **not used** in the treatment of schizophrenia; they can, in fact, **induce psychotic symptoms**. - While some antipsychotics modulate serotonin receptors, their therapeutic effect is not through agonism of these receptors. *Serotonergic receptor antagonist* - Many **atypical antipsychotics** have significant **serotonin 5-HT2A receptor antagonist** activity, in addition to D2 antagonism. - However, the question states that the patient is being switched to a **typical antipsychotic**, whose primary and defining mechanism is **D2 antagonism**, not combined serotonin-dopamine antagonism. *Cholinergic receptor agonist* - **Cholinergic receptor agonists** are **not used** to treat schizophrenia and would likely worsen symptoms or cause significant side effects. - These agents would have no therapeutic benefit in psychosis and are not part of the antipsychotic drug class.

Question 68: A 34-year-old woman is brought to the emergency department because of a 3-hour history of weakness, agitation, and slurred speech. She speaks slowly with frequent breaks and has difficulty keeping her eyes open. Over the past three days, she has had a sore throat, a runny nose, and a low-grade fever. She says her eyes and tongue have been “heavy” for the past year. She goes to bed early because she feels too tired to talk or watch TV after dinner. She appears pale and anxious. Her temperature is 38.0°C (100.4°F), pulse is 108/min, respirations are 26/min and shallow, and blood pressure is 118/65 mm Hg. On physical examination, there is bluish discoloration of her lips and around the mouth. Her nostrils dilate with every breath. The lungs are clear to auscultation. There is generalized weakness of the proximal muscles. Which of the following is the most appropriate next step in management?

A. Intravenous immunoglobulin therapy
B. Administration of edrophonium
C. Endotracheal intubation (Correct Answer)
D. Pyridostigmine therapy
E. Plasmapheresis

Explanation: ***Endotracheal intubation*** - The patient presents with clear signs of **respiratory distress** (tachypnea, shallow breathing, nostril flaring, cyanosis, and slurred speech) which indicates impending **respiratory failure**. This necessitates immediate airway management to prevent further deterioration and ensure adequate oxygenation. - Though likely a **myasthenic crisis**, the priority is to stabilize the patient's airway and breathing before confirming the diagnosis or initiating definitive treatment. *Intravenous immunoglobulin therapy* - **IVIG** is a treatment for **myasthenic crisis**, but it is not the immediate first step when respiratory failure is imminent. - **IVIG** takes time to administer and show therapeutic effect, making it unsuitable for acute respiratory compromise. *Administration of edrophonium* - **Edrophonium (Tensilon test)** is used diagnostically to confirm **myasthenia gravis**, but it is not an appropriate intervention in a patient with acute respiratory failure. - Administering **edrophonium** could worsen respiratory symptoms by causing cholinergic effects, such as increased secretions, and should not be used in an unstable patient. *Pyridostigmine therapy* - **Pyridostigmine** is a long-term treatment for **myasthenia gravis** to improve muscle strength, but it is too slow-acting for acute crisis management. - Increasing the dose of **pyridostigmine** could potentially precipitate a **cholinergic crisis**, further complicating the patient's respiratory status. *Plasmapheresis* - **Plasmapheresis** is an effective treatment for **myasthenic crisis**, but like **IVIG**, it is not an immediate life-saving measure for acute respiratory failure. - It requires setup and time, during which the patient's respiratory status could dangerously decline.

Question 69: A study is conducted to investigate the relationship between the development of type 2 diabetes mellitus and the use of atypical antipsychotic medications in patients with schizophrenia. 300 patients who received the atypical antipsychotic clozapine and 300 patients who received the typical antipsychotic haloperidol in long-acting injectable form were followed for 2 years. At the end of the observation period, the incidence of type 2 diabetes mellitus was compared between the two groups. Receipt of clozapine was found to be associated with an increased risk of diabetes mellitus relative to haloperidol (RR = 1.43, 95% p<0.01). Developed type 2 diabetes mellitus Did not develop type 2 diabetes mellitus Clozapine 30 270 Haloperidol 21 279 Based on these results, what proportion of patients receiving clozapine would not have been diagnosed with type 2 diabetes mellitus if they had been taking a typical antipsychotic?

A. 1.48
B. 0.3 (Correct Answer)
C. 0.43
D. 0.03
E. 33.3

Explanation: ***0.3*** - The question asks for the **proportion of patients** receiving clozapine who *would not have been diagnosed* with type 2 diabetes if they had been taking a **typical antipsychotic (haloperidol)**. This is essentially asking for the **attributable risk proportion** among the exposed. - First, calculate the **incidence of diabetes in the clozapine group**: 30/300 = 0.10. Then, calculate the **incidence of diabetes in the haloperidol group**: 21/300 = 0.07. The difference in incidence (attributable risk) is 0.10 - 0.07 = 0.03. To find the proportion among those exposed, divide this difference by the incidence in the clozapine group: 0.03 / 0.10 = **0.3**. *1.48* - This value is close to the **Relative Risk (RR)** of 1.43, which indicates how many times more likely the clozapine group is to develop diabetes compared to the haloperidol group. It does not represent the proportion of patients who would benefit from switching medications. - The question asks for a proportion that reflects the prevention of diabetes, not a measure of relative risk. *0.43* - This value is close to the **attributable risk fraction** (attributable risk percent / 100), which is calculated as (RR - 1) / RR = (1.43 - 1) / 1.43 = 0.43 / 1.43 ≈ 0.30. It's not a direct proportion of patients. - While related to the increased risk, 0.43 does not directly answer the question about the proportion of patients who would *not* have developed diabetes if they had taken haloperidol. *0.03* - This value represents the **absolute difference in risk (attributable risk)**: 0.10 (clozapine incidence) - 0.07 (haloperidol incidence) = 0.03. - This is the difference in incidence, not the proportion of clozapine users who would avoid diabetes if they were on haloperidol. The question asks for a proportion *among* those receiving clozapine. *33.3* - This value is likely derived from incorrect calculations or misinterpretation of the question as an alternative percentage. - It does not align with any standard epidemiological measure for comparing the impact of switching medications in the context of attributable risk or risk reduction.

Question 70: A forty-five-year-old farmer with past medical history of diabetes, hypertension, and possible narrow angles comes into your emergency room confused, diaphoretic, salivating, vomiting and shedding tears. He has pinpoint pupils. You conclude that he is showing effects of acute organophosphate poisoning. While administering the antidote, you should carefully monitor for which of the following side effects?

A. Barotrauma to middle ear
B. Bronchospasm
C. Hyperkalemia
D. Acute closed-angle glaucoma (Correct Answer)
E. Tinnitus

Explanation: ***Acute closed-angle glaucoma*** - **Atropine**, a common antidote for organophosphate poisoning, can dilate the pupils and **increase intraocular pressure**, precipitating acute closed-angle glaucoma in susceptible individuals. - The patient's history of "possible narrow angles" indicates a predisposition to this condition, making careful monitoring essential during atropine administration. *Barotrauma to middle ear* - **Barotrauma** is typically associated with changes in **ambient pressure**, such as during air travel or diving. - There is no direct physiological link between organophosphate poisoning treatment and middle ear barotrauma. *Bronchospasm* - **Organophosphate poisoning** *causes* bronchospasm due to excessive cholinergic stimulation, while atropine is used to *reverse* it. - Therefore, bronchospasm would improve, not worsen, with appropriate antidote administration. *Hyperkalemia* - **Hyperkalemia** is not a direct side effect of atropine or a common complication of organophosphate poisoning treatment. - While electrolyte imbalances can occur in critically ill patients, hyperkalemia is not specifically monitored for in this context. *Tinnitus* - **Tinnitus** is a perception of noise or ringing in the ears often associated with **auditory system damage** or certain medications. - It is not a recognized side effect of atropine or a complication to specifically monitor for in organophosphate poisoning.

Question 71: A 57-year-old woman comes to the physician for evaluation of a lump in the right breast that she first noticed a week ago. Biopsy of the mass confirms a diagnosis of a pleomorphic lobular carcinoma-in-situ that is estrogen receptor-positive. The patient undergoes lumpectomy, and treatment with tamoxifen is initiated. Which of the following conditions is most likely to occur as a result of tamoxifen therapy?

A. Ovarian cancer
B. Endometrial cancer (Correct Answer)
C. Osteoporosis
D. Myelosuppression
E. Cardiotoxicity

Explanation: ***Endometrial cancer*** - Tamoxifen acts as an **estrogen receptor agonist** in the **endometrium**, stimulating endometrial proliferation. - This proliferative effect significantly **increases the risk of endometrial hyperplasia** and **endometrial cancer** in postmenopausal women. *Ovarian cancer* - Tamoxifen is not directly linked to an increased risk of ovarian cancer. - While it affects estrogen receptors, its primary oncogenic risk is specific to the endometrium due to its agonist activity there. *Osteoporosis* - Tamoxifen acts as an **estrogen receptor agonist in bone**, which has a protective effect against bone loss. - Therefore, it typically **reduces the risk of osteoporosis**, especially in postmenopausal women, rather than causing it. *Myelosuppression* - Myelosuppression (bone marrow suppression) is a common side effect of many **chemotherapeutic agents**, but it is **not a typical side effect of tamoxifen**. - Tamoxifen's mechanism of action as a selective estrogen receptor modulator (SERM) does not primarily target rapidly dividing hematopoietic cells. *Cardiotoxicity* - **Cardiotoxicity**, such as **cardiomyopathy** or **heart failure**, is a known side effect of certain oncology drugs like **anthracyclines** (e.g., doxorubicin) and some **HER2-targeted therapies** (e.g., trastuzumab). - Tamoxifen is **not associated with significant cardiotoxicity**.

Question 72: A 61-year-old man with a history of type 1 diabetes mellitus and depression is brought to the emergency department because of increasing confusion and fever over the past 14 hours. Four days ago, he was prescribed metoclopramide by his physician for the treatment of diabetic gastroparesis. His other medications include insulin and paroxetine. His temperature is 39.9°C (103.8°F), pulse is 118/min, and blood pressure is 165/95 mm Hg. Physical examination shows profuse diaphoresis and flushed skin. There is generalized muscle rigidity and decreased deep tendon reflexes. His serum creatine kinase is 1250 U/L. Which of the following drugs is most likely to also cause this patient's current condition?

A. Fluphenazine (Correct Answer)
B. Tranylcypromine
C. Desflurane
D. Methamphetamine
E. Nortriptyline

Explanation: **Fluphenazine** - The patient's symptoms (fever, confusion, muscle rigidity, elevated CK, autonomic instability like tachycardia and hypertension) after starting metoclopramide are highly suggestive of **neuroleptic malignant syndrome (NMS)**. Metoclopramide is a **D2 receptor antagonist** that can precipitate NMS. Fluphenazine is a **typical antipsychotic** that also blocks D2 receptors and is a classic cause of NMS. - The combination of **D2 receptor blockade** (by metoclopramide) and another potent D2 blocker like fluphenazine would significantly increase the risk of NMS. *Tranylcypromine* - This drug is a **monoamine oxidase inhibitor (MAOI)**. While it can cause **serotonin syndrome** when combined with serotonergic drugs like paroxetine, the clinical picture of NMS (marked rigidity, very high fever, elevated CK) is distinct from typical serotonin syndrome. - Serotonin syndrome typically involves **hyperreflexia** and **clonus**, whereas this patient presents with **decreased deep tendon reflexes** and generalized **muscle rigidity**, key features of NMS. *Desflurane* - Desflurane is an **inhaled anesthetic** that can trigger **malignant hyperthermia** in susceptible individuals. Malignant hyperthermia shares some features with NMS (hyperthermia, muscle rigidity) but is specifically triggered by inhaled anesthetics and succinylcholine, not D2 antagonists. - Malignant hyperthermia presents acutely during or immediately after anesthesia exposure, which is not consistent with the patient's presentation following metoclopramide initiation. *Methamphetamine* - Methamphetamine is a **stimulant** that can cause hyperthermia, tachycardia, and agitation. However, it does not typically cause the profound **muscle rigidity** and significantly elevated **creatine kinase** characteristic of NMS. - The mechanism of action for methamphetamine is primarily related to increased release of dopamine, norepinephrine, and serotonin, not D2 receptor blockade leading to NMS. *Nortriptyline* - Nortriptyline is a **tricyclic antidepressant (TCA)**. While TCAs can have anticholinergic effects and cause some autonomic instability, they are not typically associated with NMS or malignant hyperthermia. - Long-term use of TCAs can occasionally contribute to **serotonin syndrome** when combined with other serotonergic agents, but NMS is not a direct result.

Question 73: A 12-year-old boy is brought by his father to a pediatrician for evaluation of stiff jaw and swallowing difficulty. He has also developed painful body spasms triggered by loud noise, light, and physical touch. His father says that a few days ago, his son continued to play football, even after falling and bruising his arms and knees. On examination, the boy had a sustained facial smile, stiff arched back, and clamped hands. The toxin responsible for these clinical manifestations that travel retrograde in axons of peripheral motor neurons blocks the release of which of the following?

A. Serotonin
B. Norepinephrine
C. Acetylcholine
D. GABA (gamma-aminobutyric acid) (Correct Answer)
E. Glutamate

Explanation: ***GABA (gamma-aminobutyric acid)*** - The patient's symptoms (stiff jaw, swallowing difficulty, painful body spasms, opisthotonos, sustained facial smile, clamped hands) are classic for **tetanus**, caused by **Clostridium tetani** producing **tetanospasmin**. - **Tetanospasmin** travels retrograde in peripheral motor neurons to the spinal cord where it blocks the release of **inhibitory neurotransmitters**, primarily **GABA and glycine**, from **Renshaw cells** and inhibitory interneurons. - Loss of inhibition leads to **unopposed excitation** of motor neurons, causing **sustained muscle contractions** (rigidity) and **spasms**. - **Glycine** is the major inhibitory neurotransmitter in the spinal cord, while **GABA** predominates in the brain; both are affected in tetanus. *Serotonin* - Serotonin is a **monoamine neurotransmitter** involved in mood, sleep, appetite, and other functions, and its release is not directly inhibited by tetanospasmin. - Disruptions in serotonin pathways are associated with psychiatric disorders or specific syndromes like **serotonin syndrome**, which presents differently with hyperthermia, altered mental status, and autonomic instability. *Norepinephrine* - Norepinephrine is a **catecholamine** involved in the sympathetic nervous system and "fight or flight" response. - While **autonomic instability** with sympathetic overactivity can occur in severe tetanus as a complication, norepinephrine release is not the primary target of tetanospasmin. - Tetanus primarily affects **inhibitory interneurons** in the spinal cord, not adrenergic neurons. *Acetylcholine* - Acetylcholine is the primary **excitatory neurotransmitter** at the **neuromuscular junction**, causing muscle contraction. - In tetanus, acetylcholine release at the neuromuscular junction is **not blocked**; instead, the problem is **lack of inhibition** of motor neurons, leading to **excessive** acetylcholine release and unopposed muscle contraction. - Contrast this with **botulism** (botulinum toxin), which *does* block acetylcholine release at the neuromuscular junction, causing flaccid paralysis. *Glutamate* - Glutamate is the main **excitatory neurotransmitter** in the central nervous system. - Tetanospasmin does not directly block glutamate release; rather, the loss of inhibitory neurotransmitters (GABA and glycine) leads to **unchecked excitation** of motor neurons by glutamate, contributing to the muscle rigidity and spasms.

Question 74: A 59-year-old man comes to the physician because of a 3-month history of frequent urination. He has to urinate every 1–2 hours during the day and wakes up at least 2–3 times at night to urinate. He also reports that over the last 2 months, he has difficulty initiating micturition and the urinary stream is weak, with prolonged terminal dribbling. His pulse is 72/min, and blood pressure is 158/105 mm Hg. Rectal exam shows a smooth, symmetrically enlarged prostate without any tenderness or irregularities. Prostate-specific antigen is within the reference range and urinalysis shows no abnormalities. A postvoid ultrasound shows a residual bladder volume of 110 mL. Which of the following is the most appropriate next step in management?

A. Transurethral resection of the prostate
B. Terazosin therapy (Correct Answer)
C. Bladder catheterization
D. Finasteride therapy
E. Cystoscopy

Explanation: ***Terazosin therapy*** - Terazosin is an **alpha-1 adrenergic antagonist** that blocks receptors in the prostate and bladder neck, causing relaxation of the smooth muscle and improving urinary flow. This is a first-line medical treatment for symptomatic **benign prostatic hyperplasia (BPH)**. - The patient presents with **obstructive and irritative lower urinary tract symptoms (LUTS)**, a symmetrically enlarged prostate, and a postvoid residual volume that indicates bladder outlet obstruction, all consistent with BPH. - Alpha-blockers provide **rapid symptom relief** (within days to weeks) and may also help with the patient's **elevated blood pressure** (158/105 mm Hg). *Transurethral resection of the prostate* - **Transurethral resection of the prostate (TURP)** is a surgical intervention reserved for patients with severe BPH symptoms refractory to medical therapy or those with complications like recurrent urinary retention or renal dysfunction. - Given that the patient has not yet tried medical therapy, and his symptoms are not immediately life-threatening, surgery is not the most appropriate first step. *Bladder catheterization* - **Bladder catheterization** is indicated for acute urinary retention or in cases of severe bladder obstruction leading to renal impairment. - While the patient has significant LUTS and a postvoid residual volume, he is not in acute urinary retention, so immediate catheterization is not necessary as a long-term management strategy. *Finasteride therapy* - **Finasteride** is a **5-alpha reductase inhibitor** that reduces prostate size by inhibiting the conversion of testosterone to dihydrotestosterone. It is more effective in patients with larger prostate volumes and takes several months to show its full effect. - Though a valid treatment for BPH, alpha-blockers like terazosin provide faster symptomatic relief by addressing dynamic obstruction and are generally preferred as initial therapy, often in combination with 5-alpha reductase inhibitors for larger prostates. *Cystoscopy* - **Cystoscopy** is an invasive procedure used to visualize the bladder and urethra directly. It is typically reserved for cases where there is suspicion of other pathologies like bladder stones, strictures, or bladder cancer, or for preoperative planning. - The patient's symptoms and examination findings are consistent with BPH, and his PSA is normal, so primary cystoscopy is not indicated as the next step in management.

Question 75: A 75-year-old male arrives by ambulance to the emergency room severely confused. His vitals are T 40 C, HR 120 bpm, BP 80/55 mmHg, RR 25. His wife explains that he injured himself about a week ago while cooking, and several days later his finger became infected, oozing with pus. He ignored her warning to see a doctor and even refused after he developed fever, chills, and severe fatigue yesterday. After being seen by the emergency physician, he was given antibiotics and IV fluids. Following initial resuscitation with IV fluids, he remains hypotensive. The ED physicians place a central venous catheter and begin infusing norepinephrine. Which of the following receptors are activated by norepinephrine?

A. Alpha 1, Alpha 2, Beta 1, Beta 2
B. Alpha 1, Alpha 2, Beta 1 (Correct Answer)
C. Alpha 2
D. Alpha 1, Beta 1, Dopamine 1
E. Alpha 1, Beta 1

Explanation: ***Alpha 1, Alpha 2, Beta 1*** - **Norepinephrine** primarily activates **alpha-1** (peripheral vasoconstriction), **alpha-2** (presynaptic inhibition and some vasoconstriction), and **beta-1** (increased heart rate and contractility) adrenergic receptors. - These are the **primary receptors** responsible for norepinephrine's clinical effects: vasoconstriction (alpha-1, alpha-2) and positive inotropic/chronotropic effects (beta-1). - This receptor profile makes norepinephrine an ideal **vasopressor** in septic shock, as seen in this patient. *Alpha 1, Alpha 2, Beta 1, Beta 2* - While **norepinephrine** does activate alpha-1, alpha-2, and beta-1 receptors, it has **negligible affinity for beta-2 receptors**. - **Epinephrine** (not norepinephrine) is the catecholamine with significant **beta-2 activity**, causing bronchodilation and vasodilation in skeletal muscle. - Including beta-2 is a common mistake when confusing norepinephrine with epinephrine. *Alpha 2* - This option is far too incomplete as **norepinephrine** has significant action on **alpha-1** and **beta-1** receptors, which are crucial for its vasoconstrictive and inotropic effects. - Activating only alpha-2 receptors would primarily lead to presynaptic inhibition and limited vasoconstriction, not the broad cardiovascular support required in septic shock. *Alpha 1, Beta 1, Dopamine 1* - While **norepinephrine** does activate **alpha-1** and **beta-1** receptors, it does **not** activate **dopamine 1 (D1) receptors**. - Only **dopamine** itself or specific **dopamine agonists** stimulate D1 receptors, leading to renal and mesenteric vasodilation. - This option incorrectly attributes dopaminergic activity to norepinephrine. *Alpha 1, Beta 1* - This option correctly identifies two of the main receptors activated by **norepinephrine**: alpha-1 (vasoconstriction) and beta-1 (positive inotropy and chronotropy). - However, it **omits alpha-2 receptors**, which norepinephrine also activates, contributing to both presynaptic feedback inhibition and additional vasoconstriction. - While not completely wrong, this is an incomplete answer.

Question 76: A 62-year-old woman is hospitalized for an open reduction of a fracture of her right femur following a motor vehicle accident 2 hours prior. She has had rheumatoid arthritis for 12 years. She was hospitalized 1 month ago for an exacerbation of rheumatoid arthritis. Since then, she has been taking a higher dose of prednisone to control the flare. Her other medications include calcium supplements, methotrexate, and etanercept. She has had appropriate nutrition over the years with regular follow-ups with her healthcare providers. Her vital signs are within normal limits. Cardiovascular examination shows no abnormalities. In order to reduce the risk of post-operative wound failure, which of the following is the most appropriate modification in this patient’s drug regimen?

A. Replacing prednisone with hydrocortisone
B. Applying topical vitamin C
C. Adding zinc supplementation (Correct Answer)
D. Discontinuing steroids before surgery
E. Increasing prednisone dose initially and tapering rapidly after 3 days

Explanation: ***Adding zinc supplementation*** - **Zinc** plays a crucial role in **collagen synthesis**, immune function, and **wound healing**, making supplementation beneficial for reducing post-operative wound failure, especially in patients with chronic inflammatory conditions or those on corticosteroids. - Chronic inflammation from **rheumatoid arthritis** and long-term **corticosteroid use** can impair zinc absorption and lead to deficiency, which exacerbates wound healing issues. *Replacing prednisone with hydrocortisone* - Both **prednisone** and **hydrocortisone** are corticosteroids, and switching between them does not inherently reduce the risk of wound failure. - While prednisone is converted to prednisolone in the liver, hydrocortisone is directly active; both have similar immunosuppressive and anti-inflammatory effects that can impair wound healing. *Applying topical vitamin C* - **Topical vitamin C** is primarily used for its antioxidant properties and role in collagen synthesis in the skin, but its systemic effect on deep surgical wound healing is limited. - **Systemic vitamin C deficiency** can impair wound healing, but the patient's history of appropriate nutrition suggests this is less likely to be the primary issue. *Discontinuing steroids before surgery* - Abruptly discontinuing **prednisone**, especially in a patient on a higher dose for an **RA flare**, carries a high risk of causing an **adrenal crisis**, which is life-threatening. - Steroids are typically continued at a stress-dose equivalent during surgery to prevent **adrenal insufficiency**, not discontinued. *Increasing prednisone dose initially and tapering rapidly after 3 days* - Increasing the **prednisone dose** pre-operatively could further suppress the immune system and impair wound healing, increasing the risk of infection and dehiscence. - While a **stress-dose steroid** regimen is appropriate, the goal is to provide physiological replacement, not to significantly increase the dose beyond what is necessary to prevent adrenal crisis.

Question 77: A neuroscientist is delivering a lecture on the electrophysiology of the brain. He talks about neuroreceptors which act as ion channels in the neurons. He mentions a specific receptor, which is both voltage-gated and ligand-gated ion channel. Which of the following receptors is most likely to be the one mentioned by the neuroscientist?

A. NMDA receptor (Correct Answer)
B. GABAA receptor
C. AMPA receptor
D. Nicotinic acetylcholine receptor
E. Glycine receptor

Explanation: ***NMDA receptor*** - The **NMDA receptor** is unique among ionotropic glutamate receptors as it functions as both a **ligand-gated** and **voltage-gated** ion channel. - It requires both the binding of an excitatory neurotransmitter (like **glutamate**) and a sufficient **depolarization** of the postsynaptic membrane to remove a **magnesium ion (Mg2+) block** from its pore. *GABAA receptor* - The **GABAA receptor** is a **ligand-gated ion channel** that opens upon binding of the neurotransmitter **GABA**, leading to an influx of chloride ions and neuronal hyperpolarization. - It is primarily responsible for **inhibitory synaptic transmission** in the central nervous system. *AMPA receptor* - The **AMPA receptor** is an ionotropic glutamate receptor that is primarily **ligand-gated**, opening swiftly upon binding of **glutamate** to allow sodium and potassium ion flow. - While it contributes to depolarization, it is generally not considered to have a significant **voltage-gating** mechanism like the NMDA receptor. *Nicotinic acetylcholine receptor* - The **nicotinic acetylcholine receptor** is a **ligand-gated ion channel** that opens in response to the binding of **acetylcholine**, initiating fast excitatory synaptic transmission. - It is **not voltage-gated** in the same manner as the NMDA receptor; its opening is primarily dependent on neurotransmitter binding. *Glycine receptor* - The **glycine receptor** is a **ligand-gated chloride channel** that mediates fast inhibitory synaptic transmission in the spinal cord and brainstem. - Its activation by **glycine** leads to an influx of chloride ions, causing hyperpolarization, and it does not exhibit significant voltage-gating properties.

Question 78: A 31-year-old man is brought to the emergency department because of fever and increasing confusion for the past day. He has bipolar disorder with psychotic features and hypothyroidism. Current medications are lithium, haloperidol, and levothyroxine. He drinks one beer with dinner every night. His speech is confused and he is oriented to person only. His temperature is 40°C (104°F), pulse is 124/min, and blood pressure is 160/110 mm Hg. He appears acutely ill. Examination shows diaphoresis and muscle rigidity. Deep tendon reflexes are 1+ bilaterally. There is minor rigidity of the neck with full range of motion. His lungs are clear to auscultation. The abdomen is soft and nontender. His leukocyte count is 15,100/mm3 and serum creatine kinase activity is 1100 U/L. Which of the following is the most likely diagnosis?

A. Delirium tremens
B. Neuroleptic malignant syndrome (Correct Answer)
C. Bacterial meningitis
D. Herpes simplex encephalitis
E. Lithium toxicity

Explanation: ***Neuroleptic malignant syndrome*** - The patient presents with **fever (40°C)**, **muscle rigidity**, **altered mental status (confusion)**, **autonomic instability (tachycardia, hypertension, diaphoresis)**, and **elevated creatine kinase**, all classic features of **Neuroleptic Malignant Syndrome (NMS)**. - The use of **haloperidol**, a high-potency antipsychotic, is a significant risk factor for NMS. *Delirium tremens* - While delirium tremens can cause altered mental status, autonomic instability, and fever, it is typically preceded by a history of **heavy chronic alcohol intake** followed by acute withdrawal, which is not indicated by "one beer with dinner every night." - **Muscle rigidity** and **marked elevation of creatine kinase** are not typical features of delirium tremens. *Bacterial meningitis* - Although bacterial meningitis presents with fever and altered mental status, it would typically involve **nuchal rigidity** that limits range of motion, which is not fully present here, and **CSF findings** (e.g., pleocytosis, low glucose) would be diagnostic. - **Profound muscle rigidity** and **markedly elevated creatine kinase** are not characteristic features of bacterial meningitis. *Herpes simplex encephalitis* - This condition presents with fever, altered mental status, and often **focal neurological deficits** or **seizures**, which are not described. - Diagnosis relies on **characteristic MRI findings** and **CSF PCR for HSV DNA**, and it would not typically cause diffuse **muscle rigidity** or **elevated creatine kinase**. *Lithium toxicity* - **Lithium toxicity** typically presents with neurological symptoms like **tremors**, **ataxia**, **nystagmus**, and altered mental status, but it is less commonly associated with **severe muscle rigidity**, **very high fever (40°C)**, or **markedly elevated creatine kinase** unless complicated by severe dehydration or NMS-like features. - A **high lithium level** would be expected, which is not mentioned as present.

Question 79: A 23-year-old man presents to his primary care physician for a runny nose, sneezing, and coughing that has persisted for a few months. He denies feeling weak or tired, but states that his symptoms have disrupted his every day life. The patient has no significant past medical history. He drinks alcohol occasionally on the weekends. His temperature is 98.6°F (37.0°C), blood pressure is 124/88 mmHg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam reveals a healthy young man who is repetitively blowing his nose. Percussion of his sinuses elicits no symptoms. Inspection of the patient's oropharynx is unremarkable. Which of the following is the best next step in management?

A. Intranasal saline
B. Diphenhydramine
C. Amoxicillin
D. Loratadine
E. Intranasal steroid (Correct Answer)

Explanation: ***Intranasal steroid*** - The patient's **persistent symptoms** (runny nose, sneezing, coughing for "a few months") that disrupt daily life, without fever or signs of infection, are highly suggestive of **allergic rhinitis**. Intranasal steroids are the **first-line treatment** for moderate to severe allergic rhinitis due to their potent anti-inflammatory effects. - They work by reducing inflammation in the nasal passages, directly targeting the underlying cause of allergic symptoms. *Intranasal saline* - While helpful for **nasal hygiene** and providing some symptomatic relief by clearing irritants, intranasal saline does not address the underlying **allergic inflammatory process**. - It is often used as an adjunct to other treatments but is not the primary or best next step for persistent, disruptive allergic rhinitis. *Diphenhydramine* - This is a **first-generation antihistamine** that can relieve allergic symptoms but is associated with significant **sedation** and **anticholinergic side effects**. - Its side effect profile makes it a less desirable choice for chronic management, especially when less sedating options are available and more effective for persistent symptoms. *Amoxicillin* - This is an **antibiotic** used to treat **bacterial infections**. The patient's symptoms are consistent with allergic rhinitis, not a bacterial infection, as evidenced by his normal temperature and lack of other systemic signs of infection. - Prescribing antibiotics in this scenario would be inappropriate and contribute to **antibiotic resistance**. *Loratadine* - This is a **second-generation oral antihistamine** that can reduce allergic symptoms with fewer side effects than diphenhydramine. However, **intranasal steroids are more effective** than oral antihistamines for comprehensive control of moderate to severe allergic rhinitis symptoms, including nasal congestion. - While a reasonable option, it is not considered the "best next step" compared to intranasal steroids for long-term management of persistent symptoms.

Question 80: A 45-year-old woman presents with recent onset movement abnormalities. She says that she noticeably blinks, which is out of her control. She also has spasms of her neck muscles and frequent leg cramps. Past medical history is significant for ovarian cancer, currently being treated with an antineoplastic agent that disrupts microtubule function and an alkylating agent, as well as metoclopramide for nausea. Her blood pressure is 110/65 mm Hg, the respiratory rate is 17/min, the heart rate is 78/min, and the temperature is 36.7°C (98.1°F). Physical examination is within normal limits. Which of the following drugs would be the best treatment for this patient?

A. Physostigmine
B. Bethanechol
C. Benztropine (Correct Answer)
D. Diazepam
E. Clozapine

Explanation: ***Benztropine*** - This patient presents with symptoms of **drug-induced parkinsonism** or **extrapyramidal symptoms (EPS)**, likely caused by **metoclopramide**, a dopamine receptor antagonist. Benztropine, an **anticholinergic agent**, is effective in blocking cholinergic overactivity in the basal ganglia, which is characteristic of EPS. - Its mechanism of action helps to restore the balance between **dopamine** and **acetylcholine** in the striatum, thereby alleviating symptoms like dystonia, akathisia, and parkinsonism. *Physostigmine* - Physostigmine is an **acetylcholinesterase inhibitor** that increases acetylcholine levels. It is used to reverse anticholinergic toxicity, which is the opposite of the current clinical need. - Administering physostigmine would worsen the patient's EPS symptoms as it would further imbalance the dopamine-acetylcholine ratio towards cholinergic dominance. *Bethanechol* - Bethanechol is a **direct cholinergic agonist** that primarily acts on muscarinic receptors in the bladder and gastrointestinal tract. It is used for urinary retention and gastrointestinal hypomotility. - This drug would not address the underlying pathophysiology of EPS and could potentially exacerbate cholinergic side effects, rather than resolving movement disorders. *Diazepam* - Diazepam is a **benzodiazepine** that enhances the effect of GABA, a major inhibitory neurotransmitter. It is used for anxiety, seizures, and muscle spasms, but it is not a primary treatment for EPS. - While it might offer some symptomatic relief for muscle spasms, it does not directly target the dopaminergic-cholinergic imbalance responsible for EPS, and it is associated with sedation and dependence. *Clozapine* - Clozapine is an **atypical antipsychotic** with potent D4 and serotonin 5-HT2A receptor antagonism, known for its low risk of EPS. It is primarily used for treatment-resistant schizophrenia. - As an antipsychotic, clozapine is not indicated for the treatment of drug-induced EPS and could potentially introduce new side effects, including agranulocytosis and myocarditis, making it an inappropriate choice for this presentation.

Question 81: A 25-year-old woman is brought to the physician by her mother because she refuses to get out of bed and spends most days crying or staring at the wall. Her symptoms started 3 months ago. The patient states that she is very sad most of the time and that none of the activities that used to interest her are interesting now. She sleeps more than 10 hours every night and naps during the day for several hours as well. Her mother, who cooks for her, says that she has been eating much larger portions than she did prior to the onset of her symptoms. The patient moved in with her mother after splitting up with her boyfriend and being expelled from her doctoral program at the local university, and she feels guilty for not being able to support herself. Two months ago, the patient was diagnosed with atypical depression and prescribed fluoxetine, which she has taken regularly since that time. Vital signs are within normal limits. Physical examination shows no abnormalities. Mental status examination shows a depressed mood and flat affect. There is no evidence of suicidal ideation. Which of the following would be contraindicated as the next step in management?

A. Taper fluoxetine and then start venlafaxine
B. Taper fluoxetine and switch to desipramine
C. Continue fluoxetine and add bupropion
D. Continue fluoxetine and add phenelzine (Correct Answer)
E. Continue fluoxetine and increase dosage

Explanation: ***Continue fluoxetine and add phenelzine*** - Combining an **SSRI** (fluoxetine) with a **MAOI** (phenelzine) is contraindicated due to the risk of **serotonin syndrome**, a potentially life-threatening condition. - Serotonin syndrome symptoms include **autonomic instability**, **neuromuscular hyperactivity**, and altered mental status. *Taper fluoxetine and then start venlafaxine* - This is a safe strategy for switching antidepressants, especially from an SSRI to an **SNRI** like venlafaxine, after an adequate washout period. - It allows for the introduction of a different mechanism of action if the initial SSRI was ineffective. *Taper fluoxetine and switch to desipramine* - Switching to a **tricyclic antidepressant (TCA)** like desipramine after tapering an SSRI can be an appropriate next step if the current medication is not effective. - TCAs have a different pharmacological profile that might be beneficial for some patients with depression. *Continue fluoxetine and add bupropion* - Adding **bupropion**, a norepinephrine-dopamine reuptake inhibitor (NDRI), to an SSRI like fluoxetine is a common and generally safe strategy for **augmenting antidepressant effects**, especially when addressing symptoms like low energy or anhedonia. - This combination can improve response rates when monotherapy is insufficient. *Continue fluoxetine and increase dosage* - If the initial dose of fluoxetine has not provided adequate relief after a sufficient trial period, increasing the dosage (within therapeutic limits) is a standard and appropriate first step before considering a switch or augmentation. - This ensures the patient is receiving an **optimal dose** of the current medication.

Question 82: A 35-year-old woman seeks evaluation at a clinic with a complaint of right upper abdominal pain for greater than 1 month. She says that the sensation is more of discomfort than pain. She denies any history of weight loss, changes in bowel habit, or nausea. Her medical history is unremarkable. She takes oral contraceptive pills and multivitamins every day. Her physical examination reveals a palpable liver mass that is 2 cm in diameter just below the right costal margin in the midclavicular line. An abdominal CT scan reveals 2 hypervascular lesions in the right hepatic lobe. The serum α-fetoprotein level is within normal limits. What is the next best step in the management of this patient’s condition?

A. Radiofrequency ablation (RFA)
B. CT-guided biopsy
C. Observation
D. Referral for surgical excision
E. Discontinue oral contraceptives (Correct Answer)

Explanation: **Discontinue oral contraceptives** - The patient's presentation with a **palpable liver mass**, **hypervascular lesions** on CT, and history of **oral contraceptive pill (OCP) use** is highly suggestive of a **hepatic adenoma**. - The first and most crucial step in managing hepatic adenomas is to **discontinue OCPs**, as this often leads to regression of the tumor. *Referral for surgical excision* - Surgical excision is considered for **large adenomas** (typically >5 cm), those that are **symptomatic** and do not regress after OCP cessation, or those with features suspicious for **malignant transformation**. - While this patient has a palpable mass, its size (2 cm) does not immediately warrant surgical excision as a first line and observation after OCP cessation is preferred. *CT-guided biopsy* - **Biopsy** is generally **avoided** in suspected hepatic adenomas due to the risk of **hemorrhage** from these highly vascular lesions and the potential for false negatives due to tumor heterogeneity. - The diagnosis is usually made clinically with imaging and reversal upon stopping OCPs. *Radiofrequency ablation (RFA)* - **RFA** is a local ablative therapy typically reserved for cases where surgery is contraindicated or for specific types of **unresectable tumors**, often in the context of hepatocellular carcinoma or metastatic disease. - It is not the initial treatment for an unconfirmed hepatic adenoma, especially before attempting OCP cessation. *Observation* - While observation is part of the management, it only follows **discontinuation of OCPs** and involves serial imaging to monitor for regression or growth. - Simply observing the patient without addressing the potential precipitating factor (OCPs) is not the best initial step.

Question 83: A 27-year-old man comes to the emergency department because of abdominal pain, diarrhea, flushing, and generalized pruritus that began after playing soccer. He also has a 2-month history of fatigue. Physical examination shows pallor and dry mucous membranes. Bone marrow biopsy shows a dense infiltration of atypical leukocytes with basophilic granules; genetic analysis of these cells shows a mutation in the KIT gene. The patient is at greatest risk for which of the following complications?

A. Stress-induced cardiomyopathy
B. Gastric ulceration
C. Mucosal neuromas
D. Tricuspid valve regurgitation
E. Laryngeal edema (Correct Answer)

Explanation: ***Laryngeal edema*** - The patient's symptoms (abdominal pain, diarrhea, flushing, pruritus, fatigue) and bone marrow findings (**dense infiltration of atypical leukocytes with basophilic granules**, **KIT gene mutation**) are highly suggestive of **systemic mastocytosis**. - **Systemic mastocytosis** involves the abnormal proliferation and accumulation of mast cells, which can degranulate and release mediators like **histamine** and **tryptase**, leading to severe allergic-like reactions including **anaphylaxis** and resultant **laryngeal edema**. *Stress-induced cardiomyopathy* - While intense exercise (like playing soccer) can cause **stress-induced cardiomyopathy** (Takotsubo cardiomyopathy), the patient's other symptoms and specific bone marrow findings point to a systemic disorder, not primarily cardiac. - This condition is typically characterized by transient left ventricular dysfunction and is not directly linked to mast cell degranulation. *Gastric ulceration* - Patients with **systemic mastocytosis** can have increased gastric acid secretion due to **histamine release**, which predisposes them to peptic ulcers. - However, the most acute and life-threatening complication in the context of a mast cell activation event (triggered by soccer, leading to flushing, pruritus, and abdominal pain) is an acute anaphylactic reaction, which includes **laryngeal edema**. *Mucosal neuromas* - **Mucosal neuromas** are a characteristic feature of **Multiple Endocrine Neoplasia type 2B (MEN2B)**, which is associated with mutations in the **RET proto-oncogene**. - This patient's symptoms and the finding of a **KIT gene mutation** are not consistent with MEN2B. *Tricuspid valve regurgitation* - **Tricuspid valve regurgitation** can be a feature of **carcinoid syndrome**, which also presents with flushing and diarrhea due to **serotonin release**. - However, the bone marrow findings and **KIT gene mutation** in this patient are specific to **systemic mastocytosis**, not carcinoid syndrome.

Question 84: A 27-year-old male arrives to your walk-in clinic complaining of neck pain. He reports that the discomfort began two hours ago, and now he feels like he can’t move his neck. He also thinks he is having hot flashes, but he denies dyspnea or trouble swallowing. The patient’s temperature is 99°F (37.2°C), blood pressure is 124/76 mmHg, pulse is 112/min, and respirations are 14/min with an oxygen saturation of 99% O2 on room air. You perform a physical exam of the patient's neck, and you note that his neck is rigid and flexed to the left. You are unable to passively flex or rotate the patient's neck to the right. There is no airway compromise. The patient's past medical history is significant for asthma, and he was also recently diagnosed with schizophrenia. The patient denies current auditory or visual hallucinations. He appears anxious, but his speech is organized and appropriate. Which of the following is the best initial step in management?

A. Propranolol
B. Diphenhydramine (Correct Answer)
C. Lorazepam
D. Dantrolene
E. Change medication to clozapine

Explanation: ***Diphenhydramine*** - The patient is presenting with acute **cervical dystonia**, likely an **acute extrapyramidal symptom (EPS)** induced by antipsychotic medication, given his recent schizophrenia diagnosis. - **Anticholinergic medications** like diphenhydramine are the first-line treatment for acute dystonia as they block muscarinic receptors and restore dopamine-acetylcholine balance in the basal ganglia. *Propranolol* - Propranolol, a **beta-blocker**, is primarily used for managing **akathisia**, another common EPS characterized by restlessness. - It would not be effective for acute dystonia, which involves sustained muscle contractions. *Lorazepam* - Lorazepam, a **benzodiazepine**, can be used as an adjunct or alternative for acute dystonia, especially if anticholinergics are ineffective or contraindicated. - However, **diphenhydramine** is generally preferred as the initial agent due to its direct anticholinergic action. *Dantrolene* - Dantrolene is a **direct skeletal muscle relaxant** and is the primary treatment for **neuroleptic malignant syndrome (NMS)**, a severe EPS with fever, altered mental status, and severe muscle rigidity. - This patient's presentation of isolated dystonia with normal vital signs does not fit the criteria for NMS. *Change medication to clozapine* - While clozapine has a lower risk of inducing EPS and is effective for refractory schizophrenia, changing chronic medication is not an appropriate initial step for an acute dystonic reaction. - The immediate priority is to alleviate the acute symptoms, and only then consider long-term medication adjustments in consultation with a psychiatrist.

Question 85: A 5-year-old is brought into the emergency department for trouble breathing. He was at a family picnic playing when his symptoms began. The patient is currently struggling to breathe and has red, warm extremities. The patient has an unknown medical history and his only medications include herbs that his parents give him. His temperature is 99.5°F (37.5°C), pulse is 112/min, blood pressure is 70/40 mmHg, respirations are 18/min, and oxygen saturation is 82% on 100% O2. Which of the following is the best initial step in management?

A. Intubation
B. Albuterol
C. Cricothyroidotomy
D. Albuterol, ipratropium, and magnesium
E. Epinephrine (Correct Answer)

Explanation: ***Epinephrine*** - This patient is exhibiting signs of **anaphylactic shock** (difficulty breathing, red/warm extremities, hypotension) likely triggered by an allergen at the picnic. **Epinephrine** is the first-line treatment for anaphylaxis due to its alpha and beta-adrenergic effects that counteract vasodilation, bronchoconstriction, and histamine release. - The rapid onset of symptoms and cardiovascular collapse (hypotension) necessitate immediate administration of epinephrine to stabilize the patient. *Intubation* - While the patient is in respiratory distress, intubation is a more invasive procedure and not the *initial* best step for anaphylactic shock. **Epinephrine** should be administered first to address the underlying physiological derangements. - Airway management, including intubation, may be necessary if epinephrine fails to improve respiratory status, but it is secondary to addressing the systemic allergic reaction. *Albuterol* - **Albuterol** is a bronchodilator that helps with bronchospasm, but it does not address the widespread vasodilation, hypotension, or other systemic effects of anaphylaxis. - While it might provide some symptomatic relief for breathing, it is insufficient as a standalone treatment for anaphylactic shock and would not prevent cardiovascular collapse. *Cricothyroidotomy* - **Cricothyroidotomy** is an emergency airway procedure used when conventional intubation is impossible due to upper airway obstruction. - In this scenario, the primary issue is systemic anaphylaxis causing bronchospasm and shock, not an isolated upper airway obstruction, making epinephrine the more appropriate initial intervention. *Albuterol, ipratropium, and magnesium* - This combination is typically used for severe asthma exacerbations, focusing on bronchodilation and smooth muscle relaxation. - Like albuterol alone, this combination does not address the underlying systemic vasodilation and hypotension characteristic of anaphylactic shock, which requires **epinephrine**.

Question 86: A 58-year-old man comes to the physician because of depressed mood for 6 months. He works as a store manager and cannot concentrate at work anymore. He experiences daytime sleepiness and fatigue because he repeatedly wakes up at night and has difficulties falling asleep again after 4 a.m. He reports no longer taking pleasure in activities he used to enjoy, such as going fishing with his son. He has decreased appetite and has had a weight-loss of 5 kg (11 lb) over the past 6 months. He does not have suicidal ideation. He has no history of serious illness and takes no medication. He is divorced and lives with his girlfriend. He drinks several alcoholic beverages on the weekends. He does not take any medications. He is diagnosed with major depressive disorder and a trial of sertraline is suggested. The patient is at greatest risk for which of the following adverse effects?

A. Delayed ejaculation (Correct Answer)
B. Postural hypotension
C. Urinary retention
D. Increased suicidality
E. Priapism

Explanation: **Delayed ejaculation** - **Sexual dysfunction**, including delayed ejaculation, is a common adverse effect of **selective serotonin reuptake inhibitors (SSRIs)** like sertraline due to their enhancement of serotonergic neurotransmission. - This side effect is particularly prevalent in male patients and can significantly impact treatment adherence and quality of life. *Postural hypotension* - **Postural hypotension** is more commonly associated with **tricyclic antidepressants (TCAs)** and some atypical antipsychotics due to their alpha-1 adrenergic blocking effects. - SSRIs generally have a **lower risk** of causing significant orthostatic changes compared to other antidepressant classes. *Urinary retention* - **Urinary retention** is primarily linked to drugs with significant **anticholinergic properties**, such as TCAs, which block muscarinic receptors. - SSRIs like sertraline have **minimal anticholinergic activity**, making urinary retention an unlikely adverse effect. *Increased suicidality* - While there is a black box warning regarding increased suicidality in children, adolescents, and young adults (under 25) when starting antidepressants, this risk is **lower in middle-aged and older adults**. - The patient's age (58) makes this a **less significant concern** compared to other populations, and he explicitly denies suicidal ideation. *Priapism* - **Priapism** (a prolonged, painful erection) is a rare but serious side effect most notably associated with **trazodone**, an antidepressant with alpha-adrenergic blocking properties. - It is **not a typical adverse effect** of SSRIs like sertraline.

Question 87: A researcher is currently working on developing new cholinergic receptor agonist drugs. He has formulated 2 new drugs: drug A, which is a selective muscarinic receptor agonist and has equal affinity for M1, M2, M3, M4, and M5 muscarinic receptors, and drug B, which is a selective nicotinic receptor agonist and has equal affinity for NN and NM receptors. The chemical structure and mechanisms of action of both drugs mimic acetylcholine. However, drug A does not have any nicotinic receptor activity and drug B does not have any muscarinic receptor activity. Which of the following statements is most likely correct regarding these new drugs?

A. Drug B may produce some of its effects by activating the IP3-DAG (inositol triphosphate-diacylglycerol) cascade
B. Drug B acts by stimulating a receptor which is composed of 5 subunits (Correct Answer)
C. Drug A acts by causing conformational changes in ligand-gated ion channels
D. Drug A acts on receptors located at the neuromuscular junctions of skeletal muscle
E. Drug A acts by stimulating a receptor which is composed of 6 segments

Explanation: ***Drug B acts by stimulating a receptor which is composed of 5 subunits*** - **Nicotinic acetylcholine receptors (nAChRs)**, which drug B agonizes, are **ligand-gated ion channels** composed of five subunits surrounding a central pore. - This pentameric structure is characteristic of all nAChRs, whether neuronal (NN) or muscle (NM) type. *Drug B may produce some of its effects by activating the IP3-DAG (inositol triphosphate-diacylglycerol) cascade* - The **IP3-DAG cascade** is a signal transduction pathway primarily associated with **G protein-coupled receptors**, specifically **M1, M3, and M5 muscarinic receptors**. - Drug B is a selective **nicotinic receptor agonist**, and nicotinic receptors are **ion channels**, not GPCRs that activate IP3-DAG. *Drug A acts by causing conformational changes in ligand-gated ion channels* - Drug A is a selective **muscarinic receptor agonist**. Muscarinic receptors are **G protein-coupled receptors (GPCRs)**, not ligand-gated ion channels. - Activation of GPCRs leads to intracellular signaling cascades, such as the **IP3-DAG or cAMP pathways**, rather than direct ion flow through a channel. *Drug A acts on receptors located at the neuromuscular junctions of skeletal muscle* - The **neuromuscular junction (NMJ)** contains **nicotinic (NM) receptors**, which mediate muscle contraction. Drug A is a selective **muscarinic receptor agonist**. - Therefore, drug A would **not act at the NMJ** to produce its effects. *Drug A acts by stimulating a receptor which is composed of 6 segments* - This statement inaccurately describes the structure of acetylcholine receptors. While some ion channels have multiple transmembrane segments, the primary classification relevant here is between **nicotinic receptors (pentameric ligand-gated ion channels)** and **muscarinic receptors (monomeric G protein-coupled receptors with 7 transmembrane domains)**, neither of which are described as being composed of "6 segments." - **Muscarinic receptors themselves are single polypeptide chains** that weave through the membrane seven times, so they are not "composed of 6 segments."

Question 88: A 72-year-old woman comes to the physician because she is seeing things that she knows are not there. Sometimes she sees a dog in her kitchen and at other times she sees a stranger in her garden, both of which no one else can see. She also reports a lack of motivation to do daily tasks for the past week. Three years ago, she was diagnosed with Parkinson disease and was started on levodopa and carbidopa. Her younger brother has schizophrenia. The patient also takes levothyroxine for hypothyroidism. She used to drink a bottle of wine every day, but she stopped drinking alcohol 2 months ago. Neurologic examination shows a mild resting tremor of the hands and bradykinesia. Her thought process is organized and logical. Which of the following is the most likely underlying cause of this patient's symptoms?

A. Alcohol withdrawal
B. Adverse effect of medication (Correct Answer)
C. Major depressive disorder
D. Schizophrenia
E. Poorly controlled hypothyroidism

Explanation: ***Adverse effect of medication*** - The patient's **visual hallucinations** and **apathy** are consistent with **dopaminergic medication-induced psychosis**, a common complication of **levodopa/carbidopa** in Parkinson's disease, especially in older patients. - The hallucinations are typically **well-formed**, non-threatening, and the patient often retains insight into their unreality, as described ("she knows are not there"). *Alcohol withdrawal* - **Alcohol withdrawal hallucinations** typically occur within 12-48 hours of cessation and are primarily visual, but often accompanied by autonomic instability (tremors, sweating, tachycardia) which is not mentioned here. - Given she stopped drinking 2 months ago, acute withdrawal symptoms would have resolved much earlier. *Major depressive disorder* - While **apathy** and lack of motivation can be symptoms of depression, the prominent **visual hallucinations** are not typical of major depressive disorder without psychotic features (which would then be a specified subtype). - Her thought process is described as **organized and logical**, making a primary thought disorder secondary to depression less likely. *Schizophrenia* - Schizophrenia typically presents in **early adulthood** (late teens to early 30s) and involves persistent psychosis, disorganized thought, and functional decline, which is not consistent with this patient's age of symptom onset or preserved thought process. - The family history of schizophrenia is a risk factor, but the clinical presentation—especially the patient's insight into the hallucinations—is more indicative of a medication-induced effect or other organic cause in an older person. *Poorly controlled hypothyroidism* - **Hypothyroidism** can cause cognitive slowing, depression, and in severe cases, myxedema madness with psychotic symptoms, but her symptoms primarily manifest as formed visual hallucinations. - There is no clinical or lab evidence provided to suggest her hypothyroidism is poorly controlled or severe enough to cause such distinct hallucinations.

Question 89: A 23-year-old woman is brought to the emergency department 30 minutes after being found unresponsive on the floor by her boyfriend. Paramedics found several empty pill bottles next to her on the floor. According to her boyfriend, she has a history of insomnia and generalized anxiety disorder and was recently diagnosed with depression. Her temperature is 36°C (96.8°F), pulse is 64/min, respirations are 10/min and shallow, and blood pressure is 112/75 mm Hg. On examination, she does not open her eyes, makes incomprehensible sounds, and extends her extremities when a painful stimulus is applied. Her pupils are 3 mm and reactive to light. The corneal reflex is normal and gag reflex is absent. There is diffuse hypotonia and decreased deep tendon reflexes. Cardiopulmonary examination shows no abnormalities. She is intubated for airway protection. Mechanical ventilation and an infusion of 0.9% saline are begun. Which of the following would most likely reverse this patient's condition?

A. Sodium bicarbonate
B. Fomepizole
C. Flumazenil (Correct Answer)
D. Dextrose
E. Naloxone

Explanation: ***Flumazenil*** - This patient presents with **central nervous system (CNS) depression** (unresponsiveness, shallow respirations, hypotonia, absent gag reflex) following suspected pill overdose, consistent with **benzodiazepine toxicity**. - **Flumazenil** is a competitive antagonist at the **GABA-A receptor**, effectively reversing the CNS depressant effects of benzodiazepines. *Sodium bicarbonate* - This is used to treat **tricyclic antidepressant (TCA) overdose**, which can cause widened QRS complexes and arrhythmias. - The patient's presentation does not suggest TCA toxicity; specifically, she does not have **cardiac conduction abnormalities**. *Fomepizole* - This is an antidote for **methanol** or **ethylene glycol poisoning**, which causes severe metabolic acidosis and can lead to organ damage. - There is no evidence of these specific intoxicants or their characteristic metabolic derangements in this patient. *Dextrose* - This is administered for **hypoglycemia**, which can cause altered mental status and unresponsiveness. - While it's a common initial intervention in altered mental status, the patient's symptoms are more indicative of a drug overdose, and there's no specific indication of **low blood glucose**. *Naloxone* - This opioid antagonist is used to reverse **opioid overdose**, which typically presents with **miosis (pinpoint pupils)**, respiratory depression, and CNS depression. - This patient has **3 mm reactive pupils**, making opioid overdose less likely as the primary cause of her symptoms.

Question 90: A 27-year-old woman presents to the emergency department because of muscle tightness and pain. She says that she has experienced increasing tightness and cramping of the muscles on the left side of her neck. She also says that she has trouble looking downwards because her “eyes are stuck.” She has a history of schizophrenia, which is being treated with haloperidol. Her temperature is 37.0°C (98.6°F), the pulse is 110/min, the respirations are 18/min, and the blood pressure is 115/71 mm Hg. Physical examination shows significant stiffness in her neck with muscle spasms. Her head is tilted severely to the left side, and her eyes are steady in upward gaze. Respiratory examination shows good air entry bilaterally with no wheezing. Which of the following medicines is the most appropriate next step in management?

A. Benztropine (Correct Answer)
B. Haloperidol
C. Lorazepam
D. Propranolol
E. Dantrolene

Explanation: ***Benztropine*** - This patient is experiencing an **acute dystonic reaction** caused by **haloperidol**, a dopamine receptor antagonist, and **benztropine** is an anticholinergic medication that effectively treats these reactions. - **Acute dystonia** presents with sustained painful muscle contractions, often affecting the neck (torticollis), eyes (oculogyric crisis), or trunk. *Haloperidol* - Administering more haloperidol would **worsen** the patient's acute dystonia, as it is the causative agent. - It works by blocking **dopamine D2 receptors**, leading to an imbalance with acetylcholine, which is what causes the dystonia. *Lorazepam* - While lorazepam (a benzodiazepine) can provide some symptomatic relief by **muscle relaxation**, it is not the primary treatment for acute dystonia. - It would not address the underlying cholinergic-dopaminergic imbalance that causes the dystonia. *Propranolol* - Propranolol is a **beta-blocker** primarily used to treat akathisia (restlessness) or tremor side effects of antipsychotics, not acute dystonia. - It would not be effective in resolving the severe muscle spasms and contractions seen in dystonia. *Dantrolene* - Dantrolene is a **muscle relaxant** often used to treat muscle rigidity and hyperthermia in conditions like **neuroleptic malignant syndrome (NMS)**. - The patient's presentation does not include features of NMS (e.g., fever, autonomic instability), making dantrolene inappropriate for acute dystonia.

Question 91: A 60-year-old man presents to the emergency department complaining of worsening exertional dyspnea over the last week. He denies chest pain and lightheadedness but reports persistent cough with white sputum. His past medical history includes hypertension and diabetes mellitus. He has a 50 pack-year history of smoking but denies any illicit drug use or alcohol consumption. His temperature is 101°F (38.3°C), blood pressure is 154/104 mmHg, pulse is 110/min, respirations are 26/min, and oxygen saturation is 88% on a non-rebreather mask. Physical exam is notable for an obese man in distress. The anteroposterior diameter of the patient's chest is increased, and he has decreased breath sounds bilaterally with diffuse expiratory wheezing. Which of the following is the best next step in management?

A. Muscarinic blocker
B. Glucocorticoid-analog
C. Alpha-2 blocker
D. Beta-2 agonist (Correct Answer)
E. Alpha-1 blocker

Explanation: ***Beta-2 agonist*** - The patient presents with **acute exacerbation of COPD**, evidenced by his significant smoking history (50 pack-years), barrel chest (increased AP diameter), decreased breath sounds, and diffuse expiratory wheezing. - **Short-acting beta-2 agonists (SABAs)** like **albuterol** are **first-line bronchodilators** in acute COPD exacerbations, providing rapid relief of bronchospasm by relaxing airway smooth muscle. - According to **GOLD guidelines**, SABAs are the primary initial bronchodilator, often combined with short-acting muscarinic antagonists (SAMAs) like ipratropium for optimal effect. - This patient requires **immediate bronchodilation** to address severe dyspnea and hypoxemia (88% on non-rebreather). *Muscarinic blocker* - **Short-acting muscarinic antagonists (SAMAs)** like **ipratropium bromide** are important adjunctive bronchodilators in acute COPD exacerbations. - While SAMAs are effective and typically used **in combination with SABAs**, they are generally considered **adjunctive rather than first-line monotherapy**. - In clinical practice, both SABAs and SAMAs are often administered together, but when asked for the "best next step," **beta-2 agonist is the more standard initial choice**. *Glucocorticoid-analog* - Systemic **glucocorticoids** like **prednisone** are indeed crucial in managing acute COPD exacerbations to reduce airway inflammation and shorten recovery time. - However, they do **not provide immediate bronchodilation**, which is the most urgent need for this patient with severe respiratory distress and hypoxemia. - Glucocorticoids are typically administered **after or concurrent with bronchodilators**, not as the initial intervention. *Alpha-2 blocker* - **Alpha-2 blockers have no role** in the management of acute respiratory distress or COPD exacerbations. - These agents are used for conditions like **hypertension** or psychiatric disorders (note: clonidine is actually an alpha-2 **agonist**, not blocker). - They do not affect airway caliber and are completely unrelated to bronchodilation. *Alpha-1 blocker* - **Alpha-1 blockers** like prazosin or doxazosin are used for **hypertension or benign prostatic hyperplasia (BPH)**. - They have **no role in acute respiratory management** or COPD exacerbations. - These agents cause peripheral vasodilation and do not affect airway smooth muscle or bronchospasm.

Question 92: A 50-year-old man comes to the physician because of gradually worsening rhythmic movements of his right hand for the past 5 months. His symptoms worsen when he is in a meeting and he is concerned that people are noticing it more frequently. There is no personal or family history of serious illness, but the patient recalls that his father developed bobbing of the head in older age. He takes no medications. Neurological examination shows a tremor of the right hand when the limbs are relaxed. When the patient is asked to move his arm the tremor decreases. He has reduced arm swing while walking. Which of the following is the most appropriate pharmacotherapy?

A. Trihexyphenidyl
B. Propranolol
C. Clonazepam
D. Donepezil
E. Levodopa/carbidopa (Correct Answer)

Explanation: ***Levodopa/carbidopa*** - The patient's symptoms (gradually worsening rhythmic movements, **resting tremor** which improves with action, reduced arm swing, and possible family history of head bobbing/tremor) are highly suggestive of **Parkinson's disease**. - **Levodopa/carbidopa** is the most effective medication for symptomatic treatment of Parkinson's disease, particularly for motor symptoms like tremor, bradykinesia, and rigidity. *Trihexyphenidyl* - This is an **anticholinergic** medication that can be used to treat tremor in Parkinson's disease, but it is generally less effective than levodopa and has more side effects, especially in older patients (e.g., confusion, dry mouth, blurred vision). - It is typically considered for younger patients with prominent tremor rather than older individuals or those with a broader range of motor symptoms. *Propranolol* - **Propranolol** is a beta-blocker primarily used to treat **essential tremor**, a condition characterized by an action or postural tremor that improves with alcohol and often has a strong family history. - The patient's tremor is a **resting tremor** that decreases with action, making essential tremor less likely. *Clonazepam* - **Clonazepam** is a benzodiazepine that is used to treat various conditions, including anxiety, seizures, and some movement disorders (e.g., restless legs syndrome, clonus). - It is not a primary treatment for Parkinson's disease tremor and would not address the other motor symptoms like reduced arm swing. *Donepezil* - **Donepezil** is an **acetylcholinesterase inhibitor** used to treat the cognitive symptoms of Alzheimer's disease and other dementias. - It has no role in the treatment of the motor symptoms of Parkinson's disease.

Question 93: A 77-year-old man with refractory shock has been under treatment in an intensive care unit for last 7 days. Despite the best possible management by the team of physicians and intensivists, he fails to show improvement. After discussion with his relatives and obtaining informed consent from them, the team administers to him a novel drug, an adrenergic agonist that produces positive chronotropic effects and inotropic effects and stimulates the release of renin from the kidneys. The drug does not have any other adrenergic effects. Which of the following second messengers is most likely to be responsible for the actions of the novel drug?

A. Calcium ion
B. Cyclic adenosine monophosphate (cAMP) (Correct Answer)
C. Cyclic guanosine monophosphate (cGMP)
D. Diacylglycerol (DAG)
E. Inositol 1,4,5-triphosphate (IP3)

Explanation: **Cyclic adenosine monophosphate (cAMP)** - The drug described is an **adrenergic agonist** with **positive chronotropic** and **inotropic effects**, and it stimulates **renin release**. These actions are characteristic of **beta-1 (β1) adrenergic receptor** activation. - Activation of β1 receptors is coupled to **G protein-coupled receptors (GPCRs)** that activate **adenylyl cyclase**, leading to an increase in intracellular **cAMP**, which acts as the second messenger. *Calcium ion* - While **calcium ions** are crucial for cardiac contractility and renin release, they are often directly modulated downstream by events initiated by second messengers like **cAMP** or **IP3/DAG**, rather than being the primary direct second messenger for β1-adrenergic stimulation. - For example, increased cAMP in cardiac cells leads to **phosphorylation of L-type calcium channels**, increasing calcium influx, but cAMP itself is the direct initiating second messenger. *Cyclic guanosine monophosphate (cGMP)* - **cGMP** is typically associated with pathways activated by **nitric oxide** and **natriuretic peptides**, leading to vasodilation and smooth muscle relaxation, which are not the primary effects described for this drug. - Drugs that activate **guanylyl cyclase** to increase cGMP would generally have opposite effects to the cardiotonic and renin-releasing actions mentioned. *Diacylglycerol (DAG)* - **DAG** is a second messenger produced along with **IP3** by the activation of **phospholipase C**, typically initiated by **alpha-1 (α1) adrenergic receptors** or other Gq-coupled GPCRs. - α1 adrenergic activation causes **vasoconstriction** and other effects, which are distinct from the positive chronotropic and inotropic actions of a β1 agonist. *Inositol 1,4,5-triphosphate (IP3)* - **IP3** is generated alongside **DAG** through the activation of **phospholipase C**, following the binding of agonists to **Gq-coupled receptors** like the α1 adrenergic receptor. - Its primary role is to trigger the release of **calcium from intracellular stores**, which, while important for muscle contraction, is not the direct second messenger pathway for the described β1-adrenergic actions.

Question 94: A 43-year-old woman presents for a routine checkup. She says she has been uncontrollably grimacing and smacking her lips for the past 2 months, and these symptoms have been getting progressively worse. Past medical history is significant for schizophrenia, managed medically with haloperidol. Which of the following is the most likely diagnosis in this patient?

A. Oculogyric crisis
B. Trismus
C. Tourette’s syndrome
D. Torticollis
E. Tardive dyskinesia (Correct Answer)

Explanation: ***Tardive dyskinesia*** - The symptoms of **uncontrollable grimacing** and **lip smacking** are classic presentations of **tardive dyskinesia**, an involuntary movement disorder. - This condition often develops after **chronic use of dopamine receptor-blocking agents**, such as typical antipsychotics like **haloperidol**. - Tardive dyskinesia typically emerges after months to years of antipsychotic therapy and is more commonly associated with first-generation (typical) antipsychotics. *Oculogyric crisis* - This is a form of **acute dystonia** characterized by **sustained upward deviation of the eyes**. - While it can be induced by antipsychotics, the present symptoms of grimacing and lip smacking are not characteristic of an oculogyric crisis. *Trismus* - Trismus refers to a **limited range of motion of the jaw** or a **sustained contraction of the jaw muscles**. - This condition primarily affects the jaw and would not explain the grimacing or lip-smacking movements. *Tourette's syndrome* - Tourette's syndrome is characterized by **multiple motor tics** and at least one **vocal tic** that persist for more than a year. - While some tics can involve facial movements, the sudden onset in adulthood after medication use points away from Tourette's, which typically presents in childhood. *Torticollis* - Torticollis, or **wry neck**, is a focal dystonia characterized by a sustained or intermittent **contraction of neck muscles**, leading to abnormal head posture. - This condition primarily affects the neck and head posture and does not explain the oral-facial dyskinesias described.

Question 95: A 46-year-old man presents to the emergency department with confusion, lacrimation, salivation, nausea, vomiting, abdominal pain, and diarrhea. He developed these symptoms 30 minutes after he finished treating his garden with the insecticide malathion. His vital signs are as follows: blood pressure is 85/50 mm Hg, heart rate is 49/min, respiratory rate is 12/min, and temperature is 36.5℃ (97.7℉). At presentation, the patient is lethargic. Physical examination reveals pallor, miosis, nystagmus, widespread bilateral loud wheezes on lung auscultation, decreased heart sounds on cardiac auscultation, abdominal tenderness, and bilaterally increased upper and lower extremities muscle tone. Which of the following statements is true?

A. Malathion activates the enzyme responsible for acetylcholine breakdown by modifying its allosteric site.
B. Maximum reaction rate (Vmax) of the affected enzyme is not changed in this patient.
C. The patient’s symptoms are caused by reversible enzyme inhibition.
D. The affected enzyme is inhibited by malathion via the formation of hydrogen bonds between its allosteric site and malathion phosphoric groups.
E. The patient’s symptoms result from the formation of covalent bonds between malathion and the affected enzyme. (Correct Answer)

Explanation: ***The patient’s symptoms result from the formation of covalent bonds between malathion and the affected enzyme.*** - Malathion is an **organophosphate insecticide** that irreversibly inhibits **acetylcholinesterase** by forming a stable **covalent bond** with a serine residue in the enzyme's active site. - This **covalent modification** prevents the enzyme from breaking down acetylcholine, leading to its accumulation and **cholinergic crisis**, which explains the patient's symptoms (confusion, lacrimation, salivation, bradycardia, wheezing, GI symptoms). *Malathion activates the enzyme responsible for acetylcholine breakdown by modifying its allosteric site.* - Malathion **inhibits**, not activates, the enzyme **acetylcholinesterase**, which is responsible for acetylcholine breakdown. - The inhibition occurs at the **active site**, not the allosteric site, via **covalent bonding**, not allosteric modification. *Maximum reaction rate (Vmax) of the affected enzyme is not changed in this patient.* - Organophosphate poisoning causes **irreversible inhibition** of acetylcholinesterase, effectively reducing the amount of functional enzyme. - This reduction in functional enzyme directly leads to a **decrease in the Vmax** of the reaction, as fewer enzyme active sites are available to process the substrate. *The patient’s symptoms are caused by reversible enzyme inhibition.* - Organophosphates like malathion are known for causing **irreversible inhibition** of acetylcholinesterase through the formation of a stable **covalent bond**, which requires the synthesis of new enzyme. - **Reversible inhibition** can be overcome by increasing substrate concentration or removing the inhibitor, which is not the case here given the severity and persistence of symptoms. *The affected enzyme is inhibited by malathion via the formation of hydrogen bonds between its allosteric site and malathion phosphoric groups.* - Malathion inhibits the enzyme by forming a **covalent bond** at the **active site**, specifically with a serine residue, rather than through hydrogen bonds at an allosteric site. - The **phosphoric groups** of malathion interact directly with the active site, leading to phosphorylation of the enzyme and its inactivation.

Question 96: A 7-year-old boy is brought in to clinic by his parents with a chief concern of poor performance in school. The parents were told by the teacher that the student often does not turn in assignments, and when he does they are partially complete. The child also often shouts out answers to questions and has trouble participating in class sports as he does not follow the rules. The parents of this child also note similar behaviors at home and have trouble getting their child to focus on any task such as reading. The child is even unable to watch full episodes of his favorite television show without getting distracted by other activities. The child begins a trial of behavioral therapy that fails. The physician then tries pharmacological therapy. Which of the following is most likely the mechanism of action of an appropriate treatment for this child's condition?

A. Increases the frequency of GABAa channel opening
B. Increases the duration of GABAa channel opening
C. Decreases synaptic reuptake of norepinephrine and dopamine (Correct Answer)
D. Blockade of D2 receptors
E. Antagonizes NMDA receptors

Explanation: ***Decreases synaptic reuptake of norepinephrine and dopamine*** - The presented symptoms (inattention, impulsivity, hyperactivity) are characteristic of **Attention-Deficit/Hyperactivity Disorder (ADHD)**. - The most common pharmacological treatments for ADHD are **stimulants** (e.g., methylphenidate, amphetamines) which work by **inhibiting the reuptake of norepinephrine and dopamine**, thereby increasing their synaptic concentrations. *Increases the frequency of GABAa channel opening* - This is the mechanism of action for **benzodiazepines**, which are primarily used for anxiety, seizures, and insomnia. - Benzodiazepines are not indicated for ADHD and would likely worsen symptoms due to their sedative effects. *Increases the duration of GABAa channel opening* - This describes the mechanism of action of **barbiturates**, which are potent central nervous system depressants. - Like benzodiazepines, barbiturates are not used for ADHD and would have inappropriate sedative side effects. *Blockade of D2 receptors* - This is the primary mechanism of action for **antipsychotic medications**, used to treat conditions like schizophrenia or bipolar disorder. - Blocking D2 receptors would likely cause side effects such as drowsiness and extrapyramidal symptoms, and would not address the core symptoms of ADHD. *Antagonizes NMDA receptors* - NMDA receptor antagonists (e.g., memantine, ketamine) are used in conditions like **Alzheimer's disease** or for anesthetic purposes. - This mechanism is not relevant to the treatment of ADHD; enhancing NMDA receptor activity might actually be beneficial in some cognitive disorders.

Question 97: A 52-year-old man presents to his primary care physician for a yearly checkup complaining of recent weight gain. The patient states that he has noticed that, regardless of his diet, his midsection has gotten increasingly larger and his old clothes no longer fit. The patient has a 2-year history of left hip arthritis from a car accident for which he is on prednisone, as well as a history of migraine headaches. The patient has also noticed that in the last 2 months, he has developed acne and his face has become fuller in appearance. On exam, the patient has gained 26 pounds since his previous checkup 1 year prior, and he now has a BMI 28.2 kg/m^2 (up from 24.1 kg/m^2 previously). His temperature is 98.3°F (36.8°C), blood pressure is 134/94 mmHg, pulse is 72/min, and respirations are 12/min. His physical exam is notable for red striae on his shoulders and around his waist. On his labs, the patient’s serum ACTH is found to be decreased. Which of the following changes is most likely expected?

A. Bilateral adrenal hyperplasia
B. Lung malignancy
C. Unilateral adrenal atrophy
D. Bilateral adrenal atrophy (Correct Answer)
E. Unilateral adrenal hyperplasia

Explanation: **Bilateral adrenal atrophy** - The patient's symptoms (weight gain, central obesity, red striae, acne, moon facies, hypertension) are consistent with **Cushing's syndrome**. - Given the history of chronic prednisone use for arthritis and decreased ACTH, this points to **exogenous corticosteroid use** causing suppression of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in bilateral adrenal atrophy. *Bilateral adrenal hyperplasia* - This would typically be seen in ACTH-dependent Cushing's syndrome, such as from a **pituitary adenoma** (Cushing's disease), where ACTH levels would be elevated or inappropriately normal, not decreased. - Adrenal hyperplasia implies increased adrenal gland size and activity, which is contrary to the expected effect of chronic exogenous steroid use. *Unilateral adrenal atrophy* - Unilateral atrophy would be highly unusual in the context of chronic exogenous steroid use, which affects both adrenal glands equally through ACTH suppression. - This might be seen if there was a **unilateral adrenal tumor** producing cortisol, leading to decreased ACTH and atrophy of the contralateral gland, but the provided ACTH level and clinical picture don't support this. *Lung malignancy* - While **small cell lung cancer** can cause Cushing's syndrome through ectopic ACTH production, this would present with **elevated ACTH** levels, contradicting the patient's decreased ACTH. - The primary context here is chronic prednisone use, making ectopic ACTH less likely. *Unilateral adrenal hyperplasia* - This could occur with a **unilateral adrenal tumor** producing cortisol, leading to Cushing's syndrome and suppressed ACTH, but would cause atrophy of the *contralateral* adrenal gland, not unilateral hyperplasia alone. - The patient's history of chronic prednisone use is the key factor, leading to bilateral suppression and atrophy.

Question 98: A 40-year-old man is brought to an urgent care clinic by his wife with complaints of dizziness and blurring of vision for several hours. His wife adds that he has had slurred speech since this morning and complained of difficulty swallowing last night. His wife mentions that her husband was working outdoors and ate stew with roasted beef and potatoes that had been sitting on the stove for the past 3 days. The patient's past medical history is unremarkable. A physical examination reveals right eye ptosis and palatal weakness with an impaired gag reflex. Cranial nerve examination reveals findings suggestive of multiple cranial nerve involvement. What is the mechanism of action of the toxin that is the most likely cause of this patient's symptoms?

A. Ribosylation of the Gs protein
B. Inhibition of glycine and GABA
C. Expression of superantigen
D. Inhibition of the release of acetylcholine (Correct Answer)
E. Ribosylation of eukaryotic elongation factor-2

Explanation: ***Inhibition of the release of acetylcholine*** - The patient's symptoms (dizziness, blurred vision, slurred speech, difficulty swallowing, ptosis, palatal weakness, impaired gag reflex, CN V and VII lesions) are consistent with **botulism**, caused by *Clostridium botulinum* toxin. - **Botulinum toxin** acts by cleaving SNARE proteins (syntaxin, SNAP-25, and synaptobrevin) at the neuromuscular junction, thereby **inhibiting acetylcholine (ACh) release** from presynaptic terminals and causing flaccid paralysis. *Ribosylation of the Gs protein* - This mechanism is characteristic of **cholera toxin** and **heat-labile enterotoxin** of *E. coli*. - It leads to persistent activation of adenylate cyclase, resulting in increased cyclic AMP and causing **secretory diarrhea**, which is not seen here. *Inhibition of glycine and GABA* - This mechanism is associated with **tetanus toxin**, produced by *Clostridium tetani*. - Tetanus toxin acts by blocking the release of inhibitory neurotransmitters **glycine** and **GABA** in the spinal cord, leading to spastic paralysis and muscle rigidity. *Expression of superantigen* - **Superantigens** are toxins produced by bacteria like *Staphylococcus aureus* (e.g., toxic shock syndrome toxin-1) and *Streptococcus pyogenes*. - They cause widespread activation of T cells, leading to a massive inflammatory response and symptoms like **fever, rash, and hypotension**, rather than neurological deficits. *Ribosylation of eukaryotic elongation factor-2* - This is the mechanism of action of **diphtheria toxin**, produced by *Corynebacterium diphtheriae*. - It inhibits protein synthesis in eukaryotic cells, leading to **cell death** and symptoms like pharyngitis, pseudomembrane formation, and myocarditis, not the paralytic symptoms described.

Question 99: A 20-year-old female presents to student health at her university for excessive daytime sleepiness. She states that her sleepiness has caused her to fall asleep in all of her classes for the last semester, and that her grades are suffering as a result. She states that she normally gets 7 hours of sleep per night, and notes that when she falls asleep during the day, she immediately starts having dreams. She denies any cataplexy. A polysomnogram and a multiple sleep latency test rule out obstructive sleep apnea and confirm her diagnosis. She is started on a daytime medication that acts both by direct neurotransmitter release and reuptake inhibition. What other condition can this medication be used to treat?

A. Obsessive-compulsive disorder
B. Bulimia
C. Attention-deficit hyperactivity disorder (Correct Answer)
D. Tourette syndrome
E. Alcohol withdrawal

Explanation: ***Attention-deficit hyperactivity disorder*** - The patient's presentation is consistent with **narcolepsy type 2 (without cataplexy)**, given the excessive daytime sleepiness, short latency to REM sleep (immediate dreaming), and exclusion of sleep apnea. The medication described, acting via **direct neurotransmitter release and reuptake inhibition**, is characteristic of a stimulant like **methylphenidate** or an amphetamine-based drug. - These stimulants are commonly used as first-line treatment for **attention-deficit hyperactivity disorder (ADHD)** due to their effects on dopamine and norepinephrine in the brain, improving focus and reducing impulsivity. *Obsessive-compulsive disorder* - **Obsessive-compulsive disorder (OCD)** is typically treated with selective serotonin reuptake inhibitors (SSRIs) or cognitive behavioral therapy. - Stimulants are not indicated for OCD and may even worsen anxiety symptoms in some individuals. *Bulimia* - **Bulimia nervosa** is often managed with a combination of psychotherapy (e.g., cognitive behavioral therapy) and antidepressants like fluoxetine. - Stimulants are not a primary treatment for bulimia and could potentially exacerbate some symptoms or risks due to their appetite-suppressing effects. *Tourette syndrome* - **Tourette syndrome** involves motor and vocal tics and is often treated with alpha-2 adrenergic agonists (e.g., guanfacine, clonidine) or dopamine receptor blocking agents. - Stimulants generally are not used for Tourette syndrome as they can sometimes worsen tics. *Alcohol withdrawal* - **Alcohol withdrawal** is a medical emergency managed with benzodiazepines to prevent seizures and delirium tremens. - Stimulants are contraindicated in alcohol withdrawal as they can increase seizure risk and cardiac complications.

Question 100: A 21-year-old female is brought by her brother to the emergency department after having a generalized tonic-clonic seizure one hour ago. She is slightly confused and has no recollection of her seizure. Her brother relayed that the patient has a history of severe anxiety for which she takes medication. For the past several days, he noticed that his sister exhibited body tremors, appeared to be agitated with quick mood changes, and, at times, was delirious. He states his sister recently ran out of her medications while visiting from out of town. Which of the following would best treat the patient's condition?

A. Varenicline
B. Naloxone
C. Methadone
D. Diazepam (Correct Answer)
E. Flumazenil

Explanation: ***Diazepam*** - The patient's presentation suggests **benzodiazepine withdrawal**, characterized by anxiety, tremors, agitation, mood swings, delirium, and seizures. **Diazepam**, a long-acting benzodiazepine, is the most appropriate treatment to reverse these withdrawal symptoms. - Benzodiazepines work by enhancing the effect of **GABA** (gamma-aminobutyric acid), an inhibitory neurotransmitter, and withdrawal leads to a state of neuronal hyperexcitability. *Varenicline* - **Varenicline** is a medication used for **smoking cessation**. - It acts as a partial agonist at nicotinic acetylcholine receptors and is not indicated for benzodiazepine withdrawal. *Naloxone* - **Naloxone** is an **opioid antagonist** used to reverse opioid overdose. - It has no role in the management of benzodiazepine withdrawal. *Methadone* - **Methadone** is a long-acting opioid agonist primarily used for **opioid dependence treatment** and chronic pain management. - It is not indicated for treating benzodiazepine withdrawal symptoms. *Flumazenil* - **Flumazenil** is a **benzodiazepine receptor antagonist** (competitive antagonist at the benzodiazepine binding site on the GABA-A receptor) used to reverse benzodiazepine overdose. - Administering **flumazenil** in a patient with benzodiazepine dependence can precipitate or worsen withdrawal symptoms, including seizures, and is therefore contraindicated.

Question 101: A 55-year-old woman seeks evaluation of difficult and incomplete voiding and spontaneous urine leakage that occurs continuously during the day and night. The symptoms are not associated with physical exertion. She denies any urethral or vaginal discharge. She is menopausal and does not take hormone replacement therapy. At 33 years of age, she had a right salpingectomy as treatment for an ectopic pregnancy. She has a 2-year history of a major depressive disorder and takes amitriptyline (100 mg before the bedtime). She was also diagnosed 5 years ago with arterial hypertension, which is controlled with enalapril (20 mg daily) and metoprolol (50 mg daily). The weight is 71 kg (156.5 lb) and the height is 155 cm (5 ft). The vital signs are as follows: blood pressure 135/80 mm Hg, heart rate 67/min, respiratory rate 13/min, and temperature 36.4℃ (97.5℉). The physical examination is significant for a palpable urinary bladder. The neurologic examination is within normal limits. The gynecologic examination shows grade 1 uterine prolapse. Which of the following is the most probable cause of the patient’s symptoms?

A. Blockage of M-cholinoreceptors (Correct Answer)
B. Blockage of β-adrenoreceptors
C. Activation of α1-adrenoceptors
D. Urethral hypermobility
E. Urethral strictures

Explanation: ***Blockage of M-cholinoreceptors*** - The patient is taking **amitriptyline**, a tricyclic antidepressant with significant **anticholinergic** properties, which can block M-cholinoreceptors in the bladder, leading to impaired detrusor contraction and difficulty voiding. - This blockage results in **urinary retention** with overflow incontinence, as evidenced by the palpable bladder and continuous urine leakage not associated with exertion. *Blockage of β-adrenoreceptors* - **Metoprolol** is a beta-blocker that primarily affects the heart and blood vessels; it does not directly impair bladder emptying or cause urinary retention by blocking β-adrenoreceptors in the bladder. - While β3-adrenoreceptors in the bladder can relax the detrusor, their blockage is not a common cause of severe voiding dysfunction and continuous leakage. *Activation of α1-adrenoceptors* - **α1-adrenoceptors** in the bladder neck and urethra cause smooth muscle contraction, contributing to urinary retention if overactive. However, none of the patient's medications are known to significantly activate these receptors in a way that would cause such severe and continuous leakage. - Activation of α1-adrenoceptors is more typically associated with conditions like benign prostatic hyperplasia in men, not directly with the described presentation in a woman. *Urethral hypermobility* - **Urethral hypermobility** is a common cause of **stress incontinence**, which involves urine leakage with physical exertion, coughing, or sneezing, and not continuous leakage day and night as described here. - The patient explicitly denies symptoms associated with physical exertion, making stress incontinence due to urethral hypermobility less likely. *Urethral strictures* - **Urethral strictures** cause **obstructive voiding symptoms** and can lead to overflow incontinence; however, they are less common in women and typically present with a history of trauma, infection, or instrumentation, which is not mentioned. - Given the patient's medication history, drug-induced anticholinergic effects are a more probable cause for the complex voiding dysfunction.

Question 102: A 58-year-old woman comes to the physician because of an itchy rash on her leg 3 days after she returned from a camping trip with her grandchildren. Examination shows a linear, erythematous, maculopapular rash on the left lower extremity. Treatment with a drug is begun that is also effective for motion sickness. One hour later, she reports dry mouth. This adverse effect is most likely mediated through which of the following?

A. Antagonism at acetylcholine receptors (Correct Answer)
B. Agonism at β-adrenergic receptors
C. Antagonism at histamine receptors
D. Antagonism at α-adrenergic receptors
E. Antagonism at serotonin receptors

Explanation: ***Antagonism at acetylcholine receptors*** - The patient likely has **poison ivy** or a similar allergic contact dermatitis, treated with a first-generation **antihistamine** (e.g., diphenhydramine) due to its known efficacy for itching and motion sickness. - Classic side effects of first-generation antihistamines like **dry mouth** (xerostomia) are primarily due to their **anticholinergic activity**, blocking muscarinic acetylcholine receptors. *Agonism at β-adrenergic receptors* - **Beta-adrenergic agonism** would typically cause effects such as **tachycardia**, bronchodilation, and tremor, and is not associated with dry mouth. - Drugs acting as β-agonists are not typically used for allergic rashes or motion sickness. *Antagonism at histamine receptors* - While the drug is an **antihistamine**, blocking histamine H1 receptors primarily alleviates **itching, allergy symptoms, and nausea/motion sickness**. - While antihistamines can cause dry mouth, this specific effect is primarily attributable to their **off-target anticholinergic action**, not direct histamine receptor antagonism. *Antagonism at α-adrenergic receptors* - **Alpha-adrenergic antagonism** (e.g., doxazosin) typically causes **vasodilation**, orthostatic hypotension, and pupillary constriction, and is not a common mechanism for dry mouth. - This mechanism is not relevant to the treatment of an itchy rash or motion sickness. *Antagonism at serotonin receptors* - **Serotonin receptor antagonism** can be involved in treating conditions like nausea (e.g., ondansetron) or migraines, but is not the primary mechanism responsible for dry mouth in this context. - While some drugs have serotonergic activity, this effect is not the direct cause of dry mouth described.

Question 103: A 55-year-old man presents with burning and shooting in his feet and lower legs, which becomes more severe at night. In the past 6 months, the pain has become much worse and disturbs his sleep. He has a history of type 2 diabetes mellitus and essential hypertension. Which of the following best represent the etiology of this patient’s condition?

A. Autonomic neuropathy
B. Distal symmetric sensorimotor polyneuropathy (Correct Answer)
C. Isolated peripheral nerve neuropathy
D. Isolated cranial nerve neuropathy
E. Radiculopathy

Explanation: ***Distal symmetric sensorimotor polyneuropathy*** - This condition is the most common form of **diabetic neuropathy**, characterized by **burning, shooting pain** predominantly in the feet and lower legs, **worsening at night**. - The patient's history of **type 2 diabetes mellitus** is a strong risk factor, and the symmetric distribution of symptoms indicates a polyneuropathy, affecting both sensory and motor nerves distally. *Autonomic neuropathy* - This involves damage to the **autonomic nervous system**, leading to symptoms like **orthostatic hypotension**, gastroparesis, or bladder dysfunction. - While common in diabetes, it does not typically present with the described **burning and shooting pain** in the extremities. *Isolated peripheral nerve neuropathy* - This diagnosis implies damage to a **single peripheral nerve**, often due to compression or trauma, resulting in focal symptoms. - The patient's symptoms are **bilateral and symmetric**, affecting multiple nerves, rather than an isolated nerve. *Isolated cranial nerve neuropathy* - This involves damage to one or more of the **cranial nerves**, leading to symptoms such as vision changes, facial weakness, or difficulty swallowing. - The described symptoms of **pain in the feet and lower legs** do not align with cranial nerve involvement. *Radiculopathy* - **Radiculopathy** refers to nerve root compression, often causing pain, numbness, or weakness in a **dermatomal or myotomal distribution**. - The patient's diffuse, symmetric symptoms in the feet and lower legs are more consistent with a polyneuropathy than a specific nerve root compression.

Question 104: A 19-year-old girl comes to the physician for evaluation after a minor motor vehicle collision. While driving down a residential street, a young boy ran out in front of her, chasing after a ball. She applied the brakes of her vehicle and avoided hitting the boy, but then she suddenly experienced generalized weakness that rendered her unable to operate the vehicle and collided at low speed with a parked car. One minute later, she recovered her strength. She was uninjured. She has had several similar episodes of transient generalized weakness over the past month, once during an argument with her mother and another time while watching her favorite comedy movie. She has also had excessive daytime sleepiness for 18 months despite 9 hours of sleep nightly and 2 daily naps. She has fallen asleep in class several times. She often sees intensely bright colors as she is falling asleep. During this time, she is often unable to move; this inability to move is very distressing to her. Which of the following is the most appropriate nighttime pharmacotherapy for this patient?

A. Sodium oxybate (Correct Answer)
B. Duloxetine
C. Amphetamine
D. Guanfacine
E. Fluoxetine

Explanation: ***Sodium oxybate*** - This patient's symptoms (excessive daytime sleepiness, **cataplexy** triggered by strong emotions, **hypnagogic hallucinations**, and **sleep paralysis**) are classic for **narcolepsy**. Sodium oxybate (gamma-hydroxybutyrate) is effective for treating both cataplexy and excessive daytime sleepiness in narcolepsy by improving **nighttime sleep quality**. - It is taken at night, typically in two doses, to help consolidate sleep and reduce the frequency and severity of narcolepsy symptoms during the day and can alleviate cataplexy. *Duloxetine* - **Duloxetine** is a **serotonin-norepinephrine reuptake inhibitor (SNRI)** primarily used to treat depression, anxiety, and neuropathic pain. While SNRIs can be used off-label to help manage cataplexy by elevating monoamine levels, they are generally not considered first-line for significant sleepiness in narcolepsy. - It would not address the primary issue of **excessive daytime sleepiness** in narcolepsy as effectively as stimulants or sodium oxybate would, and its main effect would be on improving cataplexy, not consolidating nighttime sleep. *Amphetamine* - **Amphetamines** are central nervous system stimulants primarily used to treat **excessive daytime sleepiness** in narcolepsy. However, they do not directly address cataplexy, hypnagogic hallucinations, or sleep paralysis, and are taken during the day. - The question asks for appropriate **nighttime pharmacotherapy**, and amphetamines would worsen nocturnal sleep and are not suitable for nighttime administration in narcolepsy. *Guanfacine* - **Guanfacine** is an alpha-2 adrenergic agonist primarily used to treat **attention deficit hyperactivity disorder (ADHD)** and hypertension. - It is not indicated for the treatment of narcolepsy or its associated symptoms like cataplexy, excessive daytime sleepiness, or sleep-related phenomena. *Fluoxetine* - **Fluoxetine** is a **selective serotonin reuptake inhibitor (SSRI)** commonly used for depression, anxiety, and obsessive-compulsive disorder. While SSRIs, like SNRIs, can be used to treat **cataplexy** by increasing serotonin levels, they are not typically prescribed as a primary nighttime treatment for narcolepsy's broad spectrum of symptoms. - It is generally taken in the morning to avoid potential sleep disturbances and would not address the poor nighttime sleep or daytime sleepiness as effectively as sodium oxybate, thereby failing to meet the criteria for comprehensive nighttime pharmacotherapy.

Question 105: A 53-year-old woman is brought to the emergency department by her husband because of difficulty walking, slurred speech, and progressive drowsiness. The husband reports that his wife has appeared depressed over the past few days. She has a history of insomnia and social anxiety disorder. She appears lethargic. Her temperature is 36.2°C (97.1°F), pulse is 88/min, respirations are 12/min, and blood pressure is 110/80 mm Hg. Neurologic examination shows normal pupils. There is diffuse hypotonia and decreased deep tendon reflexes. Administration of a drug that acts as a competitive antagonist at which of the following receptors is most likely to reverse this patient's symptoms?

A. D2 dopamine receptor
B. Muscarinic acetylcholine receptor
C. 5-hydroxytryptamine2 receptor
D. GABAA receptor (Correct Answer)
E. Ryanodine receptor

Explanation: ***GABAA receptor*** - The patient's symptoms of **sedation**, **slurred speech**, **ataxia** (difficulty walking), **diffuse hypotonia**, and **decreased deep tendon reflexes** are classic signs of **benzodiazepine overdose**. - **Benzodiazepines** act as **positive allosteric modulators** at the GABA-A receptor, enhancing the effects of GABA and increasing chloride influx, leading to neuronal hyperpolarization and central nervous system depression. A **competitive antagonist** like **flumazenil** can reverse these effects. *D2 dopamine receptor* - Antagonism of **D2 dopamine receptors** is associated with **antipsychotic medications** and can lead to **extrapyramidal symptoms** or neuroleptic malignant syndrome, which do not match the patient's presentation. - While dopamine receptors are involved in mood, their acute antagonism would not explain the rapid-onset, severe CNS depression described. *Muscarinic acetylcholine receptor* - **Muscarinic antagonists** (e.g., atropine, scopolamine) cause anticholinergic effects like **dry mouth**, **mydriasis**, **tachycardia**, and **delirium**, which are not observed in this patient. - Reversal of these receptors would only be indicated in cases of anticholinergic toxicity, not the present signs of CNS depression. *5-hydroxytryptamine2 receptor* - **5-HT2 receptor antagonists** are used in some antipsychotics or for migraine prophylaxis, and their primary effects are not central nervous system depression of this nature. - Overactivation or inhibition of these receptors does not typically manifest with the specific constellation of symptoms seen here (hypotonia, decreased reflexes, prominent sedation). *Ryanodine receptor* - **Ryanodine receptors** are primarily involved in **calcium release from the sarcoplasmic reticulum** in muscle cells, playing a role in muscle contraction. - Drugs acting on these receptors (e.g., dantrolene for malignant hyperthermia) affect muscle tone and contractility, but not the broad CNS depression symptoms presented in this case.

Question 106: A 70-year-old female presents to you for an office visit with complaints of forgetfulness. The patient states that over the last several years, the patient has stopped cooking for herself even though she lives alone. Recently, she also forgot how to drive back home from the grocery store and has difficulty paying her bills. The patient says she has been healthy over her whole life and does not take any medications. Her vitals are normal and her physical exam does not reveal any focal neurological deficits. Her mini-mental status exam is scored 19/30 and her MRI reveals diffuse cortical atrophy. What is the best initial treatment for this patient's condition?

A. Rivastigmine (Correct Answer)
B. Memantine
C. Bromocriptine
D. Pramipexole
E. Ropinirole

Explanation: ***Rivastigmine*** - This patient presents with symptoms and signs consistent with **Alzheimer's disease**, including gradual onset of **cognitive decline** impacting daily activities and diffuse cortical atrophy on MRI. - **Rivastigmine** is an **acetylcholinesterase inhibitor** indicated for mild-to-moderate Alzheimer's disease, which works by increasing acetylcholine levels in the brain. *Memantine* - **Memantine** is an **NMDA receptor antagonist** typically used for **moderate-to-severe Alzheimer's disease**, often in combination with acetylcholinesterase inhibitors. - While it can be beneficial, it is generally not considered the *initial* treatment for mild-to-moderate cases where acetylcholinesterase inhibitors are preferred. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** primarily used in the treatment of **Parkinson's disease** or hyperprolactinemia. - It is not indicated for the management of Alzheimer's disease and would not address the underlying cholinergic deficit. *Pramipexole* - **Pramipexole** is a **dopamine agonist** used to treat **Parkinson's disease** and restless legs syndrome. - It does not have a role in the treatment of Alzheimer's disease or other forms of dementia. *Ropinirole* - **Ropinirole** is another **dopamine agonist** primarily used for **Parkinson's disease** and restless legs syndrome. - It is not an appropriate treatment for the cognitive decline seen in Alzheimer's disease.

Question 107: A 46-year-old man presents after he accidentally got splashed with a liquid insecticide that was stored in a bucket in the storeroom one hour ago. He says that he can’t stop coughing and is having problems breathing. He also says he has a pain in his thighs which is unbearable, and his vision is blurry. His temperature is 36.7°C (98.1°F), the pulse is 130/min, the blood pressure is 144/92 mm Hg, and the respiratory rate is 20/min. On physical examination, the patient shows mild generalized pallor, moderate respiratory distress, excessive salivation, and diaphoresis. Cough is non-productive. Pupils are constricted (pinpoint). The cardiopulmonary exam reveals bilateral crepitus. The patient is administered atropine and pralidoxime, which help improve his symptoms. Which of the following is most likely to improve in this patient with the administration of atropine?

A. Muscle cramps
B. Hypertension
C. Tachycardia
D. Bronchospasm (Correct Answer)
E. Pallor

Explanation: ***Bronchospasm*** - The patient exhibits symptoms of **cholinergic crisis** due to organophosphate poisoning, including respiratory distress and excessive salivation. **Atropine** is a muscarinic antagonist that blocks the effects of acetylcholine at muscarinic receptors, thereby relieving **bronchospasm** and reducing secretions. - Relief of bronchospasm will improve breathing difficulties, a prominent symptom in this patient. *Muscle cramps* - **Organophosphate poisoning** can cause **nicotinic effects** like muscle fasciculations and cramps due to excessive acetylcholine at the neuromuscular junction. - **Atropine primarily targets muscarinic receptors** and has little to no effect on nicotinic receptors, so it would not significantly improve muscle cramps. *Hypertension* - **Organophosphate poisoning** typically causes **bradycardia and hypotension** in severe cases, although transient hypertension can occur due to sympathetic activation. - While atropine can increase heart rate, its direct effect on blood pressure in this context is complex and primarily aimed at reversing muscarinic effects rather than directly treating hypertension. *Tachycardia* - The patient presents with **tachycardia (pulse 130/min)**, which is an expected finding in symptomatic organophosphate poisoning, often compensatory to hypotension or due to central nervous system effects. - **Atropine** itself is a heart rate-elevating drug that blocks parasympathetic stimulation, so it would likely exacerbate or have no corrective effect on existing tachycardia. *Pallor* - Pallor can be a non-specific symptom, possibly related to poor circulation or anemia. - **Atropine** directly addresses muscarinic effects of organophosphate poisoning (e.g., bronchorrhea, bradycardia) and would not be expected to directly improve **pallor**.

Question 108: A 19-year-old woman is brought to the emergency room by her mother. She found her daughter pale, cold to the touch, and collapsed next to her bed earlier this morning. The patient has no previous medical or psychiatric history, but the mother does report that her daughter has not had her periods for the last 3 months. In the emergency department, the patient is alert and oriented. Her vitals include: blood pressure 80/60 mm Hg supine, heart rate 55/min. On physical examination, the patient appears pale and emaciated. A urine pregnancy test is negative. She is suspected of having an eating disorder. Which of the following treatment options would be contraindicated in this patient?

A. Olanzapine
B. Bupropion (Correct Answer)
C. Cognitive-behavioral therapy
D. Selective serotonin reuptake inhibitors
E. High caloric food

Explanation: ***Bupropion*** - **Bupropion** is contraindicated in patients with **anorexia nervosa** or **bulimia nervosa** due to the increased risk of **seizures**. - Patients with eating disorders often have electrolyte imbalances and metabolic derangements, which further lower the seizure threshold. *Olanzapine* - **Olanzapine**, an atypical antipsychotic, can be used in patients with anorexia nervosa to help with **weight gain** and reduce rigid thinking patterns. - It is particularly useful when significant **anxiety** or **psychotic features** are present, which can exacerbate the eating disorder. *Cognitive-behavioral therapy* - **Cognitive-behavioral therapy (CBT)** is a cornerstone of treatment for eating disorders, including anorexia nervosa. - It helps patients identify and change distorted thoughts and behaviors related to food, weight, and body image. *Selective serotonin reuptake inhibitors* - **SSRIs** may be used in anorexia nervosa, primarily after **weight restoration**, to address co-occurring **depression** or **anxiety disorders**. - They are generally not effective for acute weight gain but can prevent relapse and treat underlying mood disturbances. *High caloric food* - Providing **high-caloric food** and nutritional rehabilitation is essential in managing anorexia nervosa to reverse the state of **malnutrition**. - This must be done carefully to avoid **refeeding syndrome**, a potentially fatal shift in fluid and electrolytes that can occur with rapid refeeding.

Question 109: A 38-year-old man presents with sudden onset abdominal pain and undergoes an emergent laparoscopic appendectomy. The procedure is performed quickly, without any complications, and the patient is transferred to the post-operative care unit. A little while later, the patient complains of seeing people in his room and hearing voices talking to him. The patient has no prior medical or psychiatric history and does not take any regular medications. What is the mechanism of action of the anesthetic most likely responsible for this patient’s symptoms?

A. Stimulation of μ-opioid receptors
B. N-methyl-D-aspartate receptor antagonism (Correct Answer)
C. Increased duration of GABA-gated chloride channel opening
D. Blocking the fast voltage-gated Na+ channels
E. Increased frequency of GABA-gated chloride channel opening

Explanation: ***N-methyl-D-aspartate receptor antagonism*** - The patient's symptoms of **hallucinations** and **auditory phenomena** post-anesthesia are characteristic of **emergence delirium**, often associated with **ketamine**. - Ketamine acts primarily as an **NMDA receptor antagonist**, which can lead to dissociative anesthesia and psychomimetic effects upon emergence. *Stimulation of μ-opioid receptors* - Opioids primarily cause **analgesia**, respiratory depression, and sedation by stimulating **μ-opioid receptors**. - While opioids can cause some central nervous system effects like confusion or nightmares, the severe **hallucinations** described are not typical for this mechanism. *Increased duration of GABA-gated chloride channel opening* - This mechanism describes the action of **benzodiazepines** which potentiate GABAergic neurotransmission by increasing the **frequency** of chloride channel opening, while **barbiturates** increase the **duration**. - These drugs typically cause **sedation** and **anxiolysis**, not acute psychosis or vivid hallucinations upon emergence. *Blocking the fast voltage-gated Na+ channels* - This is the primary mechanism of action for **local anesthetics** and certain **antiarrhythmic drugs**, leading to inhibition of nerve impulse conduction. - While some systemic toxicity can occur with local anesthetics, it typically manifests as **seizures** or cardiovascular collapse, not dissociative emergence phenomena. *Increased frequency of GABA-gated chloride channel opening* - This is the mechanism of action for **benzodiazepines**, which enhance GABA's inhibitory effects by increasing the **frequency** of chloride channel opening. - Similar to increased duration of opening, this leads to **sedation** and anxiolysis, not the vivid hallucinations seen in this patient.

Question 110: A 38-year-old woman comes to the physician because of a 3-week history of involuntary movements of her extremities. One year ago, she was fired from her position as an elementary school teacher because she had stopped preparing lessons and was frequently absent without notice. She now lives with her mother. She appears emaciated and malodorous. Examination shows rapid, nonrepetitive jerks of her limbs and face that frequently end with the patient covering her face and yawning. She has an unsteady gait. Genetic testing shows a mutation on chromosome 4. This patient's condition is most likely associated with increased levels of which of the following substances?

A. Gamma-aminobutyric acid
B. N-acetyl aspartate
C. Glutamate (Correct Answer)
D. Dopamine
E. Acetylcholine

Explanation: ***Glutamate*** - **Huntington's disease** is characterized by **chorea, psychiatric symptoms, and cognitive decline**, caused by CAG repeat expansion on chromosome 4 producing abnormal huntingtin protein. - The mutant huntingtin protein leads to **glutamate excitotoxicity** through multiple mechanisms: impaired glutamate reuptake, enhanced NMDA receptor sensitivity, and mitochondrial dysfunction. - **Increased glutamatergic activity and extracellular glutamate levels** contribute to progressive neuronal death, particularly of GABAergic medium spiny neurons in the striatum. - This glutamate-mediated excitotoxicity is the primary mechanism driving neurodegeneration in Huntington's disease. *Gamma-aminobutyric acid (GABA)* - GABAergic neurons in the striatum are preferentially lost in Huntington's disease, resulting in **decreased GABA levels**, not increased. - The loss of GABAergic inhibition contributes to **disinhibition of motor pathways** and the characteristic choreiform movements. *N-acetyl aspartate (NAA)* - NAA is a neuronal marker that is **decreased** in neurodegenerative diseases like Huntington's, reflecting **neuronal loss and dysfunction**. - Reduced NAA is seen on MR spectroscopy but does not cause the motor symptoms. *Dopamine* - While there is **relative dopamine hyperactivity** in the striatum due to loss of GABAergic inhibition, dopamine levels themselves are not necessarily increased. - Dopamine-depleting agents (e.g., **tetrabenazine, deutetrabenazine**) are used therapeutically to reduce chorea by decreasing dopaminergic transmission. *Acetylcholine* - Acetylcholine levels are **not primarily elevated** in Huntington's disease pathophysiology. - Cholinergic function may be affected in advanced disease contributing to cognitive symptoms, but this is not the primary mechanism of chorea.

Question 111: An 18-year-old man is known to be allergic to peanuts, and he mistakenly eats biscuits containing some traces of peanuts. Within 15 minutes, he develops generalized redness of the skin and urticaria, associated with shortness of breath and diffuse wheezing. His blood pressure is 80/55 mm Hg and heart rate is 124/min. He is given intramuscular epinephrine and transported emergently to the local hospital. This patient’s presentation is an example of which of the following hypersensitivity reactions?

A. Delayed hypersensitivity
B. Immediate hypersensitivity (Correct Answer)
C. Type II hypersensitivity
D. Contact dermatitis
E. Serum sickness

Explanation: ***Immediate hypersensitivity*** - The rapid onset (within 15 minutes) of symptoms like **generalized redness**, **urticaria**, **shortness of breath**, **wheezing**, and **hypotension** after exposure to peanuts is characteristic of an **anaphylactic reaction**, which is a severe form of immediate (Type I) hypersensitivity. - This reaction involves **IgE-mediated mast cell and basophil degranulation**, leading to the rapid release of histamine and other inflammatory mediators. *Delayed hypersensitivity* - This type of hypersensitivity, also known as **Type IV hypersensitivity**, typically manifests 24 to 72 hours after antigen exposure. - It is mediated by **T-cells** and macrophages, not antibodies, and is commonly seen in reactions like **tuberculin skin tests** or contact dermatitis. *Type II hypersensitivity* - This reaction involves **antibody-mediated cytotoxicity**, where antibodies (IgG or IgM) bind to antigens on cell surfaces, leading to cell destruction. - Examples include **hemolytic transfusion reactions** and **autoimmune hemolytic anemia**, which do not match the presented symptoms. *Contact dermatitis* - This is a form of **Type IV hypersensitivity** that results from direct contact of the skin with an allergen, leading to a localized rash. - It presents with **localized skin inflammation** and typically has a delayed onset, usually days after exposure, unlike the rapid systemic reaction described. *Serum sickness* - This is a **Type III hypersensitivity reaction** characterized by the formation of **immune complexes** that deposit in tissues, causing symptoms like fever, rash, and arthralgia. - It typically occurs days to weeks after exposure to certain drugs or foreign proteins, which does not align with the immediate, severe systemic symptoms.

Question 112: A 23-year-old woman presents to the emergency department with acute onset of shortness of breath, wheezing, and chest tightness. This is her 4th visit for these symptoms in the last 5 years. She tells you she recently ran out of her normal "controller" medication. Concerned for an asthma exacerbation, you begin therapy with a short-acting beta2-agonist. What is the expected cellular response to your therapy?

A. Gs protein coupled receptor activates adenylyl cyclase and increases intracellular cAMP (Correct Answer)
B. Gq protein coupled receptor activates phospholipase C and increases intracellular calcium
C. Gq protein coupled receptor activates adenylyl cyclase and increases intracellular cAMP
D. Gs protein coupled receptor activates phospholipase C and increases intracellular calcium
E. Gi protein coupled receptor inhibits adenylyl cyclase and decreases cAMP

Explanation: ***Gs protein coupled receptor activates adenylyl cyclase and increases intracellular cAMP*** - **Short-acting beta2-agonists (SABAs)** like **albuterol** bind to **beta2-adrenergic receptors** on airway smooth muscle cells, which are **Gs protein-coupled receptors**. - Activation of **Gs protein** stimulates **adenylyl cyclase**, leading to an increase in intracellular **cyclic AMP (cAMP)**, which triggers downstream relaxation of bronchial smooth muscle. *Gq protein coupled receptor activates phospholipase C and increases intracellular calcium* - **Gq protein-coupled receptors** are typically associated with **alpha1-adrenergic receptors** or **muscarinic M1/M3 receptors**, which, when activated, cause **bronchoconstriction** not bronchodilation. - Activation of **Gq protein** leads to activation of **phospholipase C**, which generates **IP3** and **DAG**, ultimately increasing intracellular **calcium** and promoting contraction. *Gq protein coupled receptor activates adenylyl cyclase and increases intracellular cAMP* - This option incorrectly pairs **Gq protein** with the activation of **adenylyl cyclase** and an increase in **cAMP**. - **Gq protein** signaling primarily involves the **phospholipase C pathway** and **calcium** mobilization, not direct adenylyl cyclase activation. *Gs protein coupled receptor activates phospholipase C and increases intracellular calcium* - This option incorrectly pairs **Gs protein** with the activation of **phospholipase C** and an increase in intracellular **calcium**. - **Gs protein** is specifically coupled to the **adenylyl cyclase/cAMP pathway**, while **phospholipase C** and **calcium** are associated with **Gq protein** signaling. *Gi protein coupled receptor inhibits adenylyl cyclase and decreases cAMP* - **Gi protein-coupled receptors** inhibit **adenylyl cyclase** and decrease intracellular **cAMP**, which would lead to **bronchoconstriction**, not bronchodilation. - This mechanism is associated with **M2 muscarinic receptors** on presynaptic terminals, which regulate acetylcholine release, or alpha2-adrenergic receptors, which are not the primary target for bronchodilation in asthma exacerbations.

Question 113: A 23-year-old male is brought by police officers from a social gathering due to combative behavior and altered mental status. The police say that phencyclidine was found on the premises. The patient is alone, and acquiring an accurate history proves difficult. However, you do learn that the patient is having visual hallucinations. Vital signs show a blood pressure of 155/95 mmHg, pulse is 103/min, respirations is 20/min, oxygen saturation of 99%. Airway, breathing, and circulation are intact. The patient appears violent, and is trying to remove his clothes. Multiple hospital staff are needed to restrain the patient in bed. A finger-stick glucose show 93 mg/dL. The team is unable to place an IV, and thus intramuscular midazolam is administered to achieve sedation; however, he is still agitated. What is the mechanism of action of the best alternative sedative drug for this patient?

A. Mu-opioid receptor partial agonist
B. Competitive opioid receptor antagonist
C. Alpha-2 and H1 receptor antagonist
D. Increases duration of chloride channel opening of GABA-A receptors
E. Antagonist of D2 receptors (Correct Answer)

Explanation: ***Antagonist of D2 receptors*** - The patient is likely suffering from **phencyclidine (PCP) intoxication**, characterized by **agitation**, **combative behavior**, **altered mental status**, **hypertension**, **tachycardia**, and **visual hallucinations**. - **Haloperidol**, a potent **D2 dopamine receptor antagonist**, is often the preferred second-line treatment for agitation in PCP intoxication when benzodiazepines are insufficient, as it effectively reduces the psychotic and agitated state. *Mu-opioid receptor partial agonist* - This mechanism describes drugs like **buprenorphine**. While used for opioid addiction, it is not an appropriate sedative for acute PCP intoxication. - Using an opioid agonist or partial agonist in a combative, agitated patient with unclear history could worsen respiratory depression or complicate the clinical picture. *Competitive opioid receptor antagonist* - This describes **naloxone**, used to reverse opioid overdose. It would not be helpful for PCP intoxication, as PCP acts via different receptor systems (NMDA antagonism, dopamine reuptake inhibition). - Administering naloxone in this scenario would have no therapeutic benefit for the patient's agitation and psychosis. *Alpha-2 and H1 receptor antagonist* - This describes the mechanism of drugs like **mirtazapine** (primarily antidepressant) or **clonidine** (alpha-2 agonist, not antagonist, used for sedation/hypertension but less effective for acute psychotic agitation). - While some antipsychotics have H1 antagonism, this specific combination is not the primary mechanism of the most effective conventional antipsychotics used for severe agitation. *Increases duration of chloride channel opening of GABA-A receptors* - This mechanism describes **barbiturates**. While some barbiturates can cause sedation, they are generally not preferred as first-line agents in this situation due to a higher risk of respiratory depression and a narrow therapeutic index compared to benzodiazepines or antipsychotics. - The initial intramuscular midazolam (a benzodiazepine) works by increasing the *frequency* of chloride channel opening, not duration, making this option incorrect for the *best alternative*.

Question 114: A 36-year-old man is brought to the emergency department because of facial spasm and an inability to speak for 2 hours. He has had no loss of consciousness or rhythmic movements. He has a history of schizophrenia and was recently put on clozapine for resistant symptoms. He appears to be aware of his surroundings. At the hospital, his blood pressure is 135/85 mm Hg, the pulse is 86/min, the respirations are 16/min, and the temperature is 36.7°C (98.1°F). Physical examination shows the superior deviation of both eyes to the right side, trismus, and spasm of the neck muscles with a deviation of the head to the left. He follows directions without hesitation. The remainder of the physical examination shows no abnormalities. The most appropriate next step is to administer which of the following?

A. Labetalol
B. Diphenhydramine (Correct Answer)
C. Flumazenil
D. Calcium gluconate
E. Morphine

Explanation: ***Diphenhydramine*** - The patient's symptoms (facial spasm, inability to speak, ocular deviation, trismus, neck muscle spasm) are characteristic of **acute dystonia**, a **drug-induced extrapyramidal symptom (EPS)**. - While **clozapine** has a **low risk of EPS** compared to typical antipsychotics due to its weak D2 receptor binding, acute dystonia can still rarely occur, particularly when initiating therapy. - **Anticholinergic medications** like diphenhydramine (an antihistamine with anticholinergic properties) or benztropine are the **first-line treatment** for acute dystonia, quickly relieving symptoms by restoring the **dopamine-acetylcholine balance** in the basal ganglia. - Symptoms typically resolve within **15-30 minutes** of parenteral administration. *Labetalol* - Labetalol is a **beta-blocker** used to treat **hypertensive emergencies** or **tachycardia**. - The patient's blood pressure (135/85 mm Hg) and pulse (86/min) are within normal range, and there is no indication for antihypertensive therapy. *Flumazenil* - Flumazenil is a **benzodiazepine receptor antagonist** used to reverse **benzodiazepine overdose**. - The patient's symptoms are not consistent with benzodiazepine toxicity (which would present with sedation, respiratory depression, or altered consciousness), and there is no mention of benzodiazepine use. *Calcium gluconate* - Calcium gluconate is used to treat **hypocalcemia**, stabilize cardiac membranes in **hyperkalemia**, or reverse **calcium channel blocker toxicity**. - There is no clinical or laboratory evidence of electrolyte imbalance or calcium channel blocker exposure. *Morphine* - Morphine is an **opioid analgesic** used for **severe pain management**. - The patient's primary complaint is involuntary muscle spasms and dystonia, not pain, and opioids are not indicated for the treatment of acute dystonia.

Question 115: A 71-year-old man arrives to the emergency room appearing cyanotic and having weak, shallow respirations. He is brought in by his home care nurse, who reports that the patient has a history of myasthenia gravis and frequent urinary tract infections. The patient was in his normal state of health until 5 days ago when he developed a urinary tract infection. He was prescribed gentamicin with improvement of his urinary symptoms. This morning, while trying to eat breakfast, he began complaining of poor grip strength and progressive difficulty breathing. The patient’s medications include pyridostigmine and aspirin, both of which his nurse reports he takes every day as prescribed. The patient’s temperature is 99°F (37.2°C), blood pressure is 128/78 mmHg, pulse is 92/min, and respirations are 28/min with an oxygen saturation of 86% O2 on room air. Upon physical exam, the patient is noted to have gray-blue skin, hypophonia, weak upper extremities, and normal leg strength. An arterial blood gas is drawn with results as shown below: PO2: 55 mmHg PCO2: 60 mmHg pH: 7.30 The patient is intubated. Which of the following is the next best step in management?

A. Plasmapheresis (Correct Answer)
B. Thymectomy
C. Neostigmine
D. Edrophonium
E. Atropine

Explanation: ***Plasmapheresis*** - The patient is experiencing a **myasthenic crisis**, characterized by **respiratory failure** and worsening muscle weakness, likely precipitated by the **gentamicin** (an aminoglycoside known to exacerbate myasthenia gravis). - **Plasmapheresis** or **intravenous immunoglobulin (IVIG)** are the first-line treatments for myasthenic crisis to rapidly remove circulating autoantibodies and improve neuromuscular transmission. *Thymectomy* - **Thymectomy** is considered for patients with **thymoma** or generalized myasthenia gravis, but it is an elective surgical procedure and not an acute management for a myasthenic crisis. - While it can induce remission or improve symptoms in the long term, it is not the immediate next step for a patient in respiratory distress. *Neostigmine* - **Neostigmine** is a **cholinesterase inhibitor** used for symptomatic treatment of myasthenia gravis, but administering additional cholinesterase inhibitors during a myasthenic crisis can paradoxically worsen weakness if it is a **cholinergic crisis** (though less likely here given the history and precipitating factor). - The patient is already on **pyridostigmine**, and increasing cholinergic agents can lead to an accumulation of acetylcholine, causing **desensitization of receptors** and further paradoxically worsening weakness. *Edrophonium* - **Edrophonium** is a **short-acting cholinesterase inhibitor** used in the **Tensilon test** to differentiate between myasthenic crisis and cholinergic crisis. - It is a diagnostic tool and not a definitive treatment for a severe myasthenic crisis requiring intubation. *Atropine* - **Atropine** is an **anticholinergic agent** used to counteract muscarinic side effects of cholinesterase inhibitors, such as bradycardia or excessive secretions, especially if a cholinergic crisis is suspected. - It does not address the underlying autoimmune attack on neuromuscular junctions and is not a primary treatment for the weakness in a myasthenic crisis.

Question 116: A 20-year-old female presents to your clinic for evaluation. She complains of months of daily rhinorrhea, which she describes as watery and clear, as well as nasal congestion bilaterally. In addition, she reports frequent watery and itchy eyes, as well as daily sneezing. Her temperature is 100.1 deg F (37.8 deg C), blood pressure is 120/70 mmHg, pulse is 70/min, and respirations are 15/min. On exam, you note edematous, boggy turbinates with watery rhinorrhea. Which of the following is a treatment for the patient's condition?

A. Intravenous vancomycin
B. Intravenous penicillin
C. Oral acetaminophen
D. Intranasal fluticasone (Correct Answer)
E. Oral amoxicillin

Explanation: ***Intranasal fluticasone*** - The patient's symptoms of **watery rhinorrhea**, bilateral **nasal congestion**, **itchy eyes**, and **sneezing** are classic for **allergic rhinitis**. - **Intranasal corticosteroids** such as fluticasone are highly effective first-line treatments for managing the inflammation and symptoms of allergic rhinitis. *Intravenous vancomycin* - **Vancomycin** is an **antibiotic** used to treat serious bacterial infections, particularly those caused by **methicillin-resistant Staphylococcus aureus (MRSA)**. - The patient's symptoms are characteristic of an allergic reaction, not a bacterial infection, and thus antibiotics are inappropriate. *Intravenous penicillin* - **Penicillin** is an **antibiotic** used to treat a wide range of bacterial infections. - Given the symptoms of allergy, there is no indication for antibiotic therapy. *Oral acetaminophen* - **Acetaminophen** is an **analgesic** and **antipyretic** used to relieve pain and fever. - While the patient has a mild fever (100.1 deg F), her primary symptoms are allergic, not indicative of pain or a severe febrile illness requiring this medication as a primary treatment for her *condition*. *Oral amoxicillin* - **Amoxicillin** is a broad-spectrum **antibiotic** commonly used for bacterial infections. - Its use is not indicated here as the patient's presentation aligns with allergic rhinitis, not a bacterial infection.

Question 117: An 18-year-old female is brought to the emergency department by her boyfriend. She is screaming uncontrollably. Eventually, she states that she is afraid that "death is near" but cannot give a rational reason for this thought. She reports both seeing colors "coming out of other people's mouths" and "hearing" these colors. The patient's boyfriend experienced similar sensory symptoms a few hours ago; he explains they were trying to have a "spiritual experience." Physical exam is significant for mydriasis, hypertension, hyperthermia, piloerection, tachycardia, and sweating. Upon which of the following receptors does the most likely drug she ingested act?

A. 5-hydroxytryptamine (Correct Answer)
B. Cannabinoid
C. NMDA
D. Mu opioid
E. GABA

Explanation: ***5-hydroxytryptamine*** - The patient's symptoms, including **hallucinations** (seeing and hearing colors), **delusions** ("death is near"), and **autonomic hyperactivity** (mydriasis, hypertension, tachycardia, hyperthermia, sweating), are classic for **serotonergic hallucinogen** intoxication. - Classic serotonergic hallucinogens like **LSD** (lysergic acid diethylamide) and psilocybin act primarily as partial agonists at the **5-HT2A serotonin receptors** in the brain. *Cannabinoid* - While cannabinoids (e.g., from cannabis) can cause altered perception and tachycardia, they typically do not produce the same level of **pronounced hallucinations**, **delusions**, or the full spectrum of **autonomic hyperactivity** seen here. - Cannabinoids primarily act on **cannabinoid receptors (CB1 and CB2)**, not 5-HT receptors. *NMDA* - **NMDA receptor antagonists** (e.g., phencyclidine [PCP], ketamine) can cause hallucinations and agitation, but their classic presentation often includes **nystagmus**, **dissociative anesthetic effects**, and severe **aggression**, which are not centrally highlighted in this case. - These drugs block the N-methyl-D-aspartate (NMDA) receptor, a glutamate receptor. *Mu opioid* - **Mu opioid receptor agonists** (e.g., heroin, morphine) cause central nervous system depression, miosis (pinpoint pupils), respiratory depression, and euphoria. - The patient's presentation with **mydriasis**, **agitation**, and **autonomic overactivity** is the opposite of opioid intoxication. *GABA* - **GABA-A receptor agonists** (e.g., benzodiazepines, barbiturates) are central nervous system depressants that cause sedation, anxiolysis, and muscle relaxation. - The patient's symptoms of extreme **agitation**, **hallucinations**, and **autonomic arousal** are inconsistent with GABAergic drug effects.

Question 118: A 29-year-old man is outside his home doing yard work when a bee stings him in the right arm. Within 10 minutes, he reports breathlessness and multiple, circular, pruritic rashes over his right arm. He drives to his family physician’s office for evaluation. His past medical history is significant for hypertension and he takes lisinopril. Known allergies include latex, Hymenoptera, and aspirin. His blood pressure is 118/68 mm Hg; heart rate is 104/min and regular; respiratory rate is 22/min; temperature is 37.7°C (99.8°F). There is non-pitting edema but erythema with raised wheels are present in the region of the right arm. Auscultation of the lungs reveals mild wheezing at the lung bases. Which of the following is the best course of action in the management of this patient?

A. Go to the emergency department
B. Methylprednisolone and go to the emergency department
C. Diphenhydramine and go to the emergency department
D. Epinephrine and go to the emergency department (Correct Answer)
E. Albuterol and go to the emergency department

Explanation: ***Epinephrine and go to the emergency department*** - This patient is experiencing **anaphylaxis**, indicated by breathlessness, generalized urticaria, and a known bee sting allergy, which requires immediate treatment with **epinephrine**. - **Epinephrine** is the first-line and most critical treatment for anaphylaxis as it reverses bronchoconstriction, stabilizes mast cells, and increases blood pressure. After administering epinephrine, prompt transfer to the **emergency department** is essential for monitoring and further management. *Go to the emergency department* - While going to the emergency department is necessary, it is not sufficient as the **initial and most critical treatment (epinephrine)** is missing. - Delaying the administration of epinephrine for anaphylaxis can lead to rapid deterioration and life-threatening complications. *Methylprednisolone and go to the emergency department* - **Methylprednisolone (corticosteroids)** can help prevent biphasic anaphylaxis and reduce inflammation but are **not a first-line treatment for acute anaphylaxis** and do not provide immediate relief from bronchospasm or hypotension. - The immediate priority is addressing the acute symptoms with epinephrine, followed by transport to the emergency department, where corticosteroids may be administered. *Diphenhydramine and go to the emergency department* - **Diphenhydramine (an antihistamine)** can help alleviate mild cutaneous symptoms like pruritus and urticaria, but it **does not treat the life-threatening respiratory or cardiovascular symptoms** of anaphylaxis. - It should not be used as the sole or primary treatment for anaphylaxis, especially in the presence of breathlessness. *Albuterol and go to the emergency department* - **Albuterol (a bronchodilator)** can help relieve bronchospasm and breathlessness, but it **does not address other critical aspects of anaphylaxis** such as vasodilation or mast cell stabilization. - While useful as an adjunct, it is not a substitute for epinephrine in the management of systemic anaphylaxis.

Question 119: A 55-year-old man comes to the physician with a 3-month history of headache, periodic loss of vision, and easy bruising. Physical examination shows splenomegaly. His hemoglobin concentration is 13.8 g/dL, leukocyte count is 8000/mm3, and platelet count is 995,000/mm3. Bone marrow biopsy shows markedly increased megakaryocytes with hyperlobulated nuclei. Genetic analysis shows upregulation of the JAK-STAT genes. The pathway encoded by these genes is also physiologically responsible for signal transmission of which of the following hormones?

A. Oxytocin
B. Adrenocorticotropic hormone
C. Prolactin (Correct Answer)
D. Cortisol
E. Insulin

Explanation: ***Prolactin*** - Prolactin utilizes the **JAK-STAT signaling pathway** to exert its effects on target cells, particularly in the mammary glands. - The **JAK-STAT pathway** is crucial for cell growth, differentiation, and immune response, and its dysregulation is linked to myeloproliferative disorders like those involving megakaryocyte proliferation. *Oxytocin* - Oxytocin primarily acts through **G-protein coupled receptors** that activate the phospholipase C/inositol triphosphate pathway, not the JAK-STAT pathway. - Its main roles involve uterine contraction and milk ejection, which are distinct from the cellular proliferation regulated by JAK-STAT. *Adrenocorticotropic hormone* - ACTH binds to **G-protein coupled receptors** in the adrenal cortex, stimulating adenylyl cyclase and increasing cAMP levels. - This mechanism of action is distinct from the tyrosine kinase activity characteristic of the JAK-STAT pathway. *Cortisol* - Cortisol, a steroid hormone, primarily acts via **intracellular glucocorticoid receptors** that translocate to the nucleus to regulate gene transcription. - Its signaling mechanism involves direct gene regulation rather than a membrane-bound receptor-kinase cascade like JAK-STAT. *Insulin* - Insulin signals through a **receptor tyrosine kinase**, which, upon binding, autophosphorylates and initiates a cascade involving IRS proteins and the PI3K/Akt and MAPK pathways. - While it involves tyrosine phosphorylation, it is distinct from the JAK-STAT pathway, which is primarily activated by cytokine and growth hormone type I receptors.

Question 120: A 42-year-old female complains of feeling anxious and worrying about nearly every aspect of her daily life. She cannot identify a specific cause for these symptoms and admits that this tension is accompanied by tiredness and difficulty falling asleep. To treat this problem, the patient is prescribed sertraline. She endorses a mild improvement with this medication, and over the next several months, her dose is increased to the maximum allowed dose with modest improvement. Her psychiatrist adds an adjunctive treatment, a medication which notably lacks any anticonvulsant or muscle relaxant properties. This drug most likely acts at which of the following receptors?

A. Beta adrenergic receptor
B. 5HT-1A receptor (Correct Answer)
C. GABA receptor
D. Alpha adrenergic receptor
E. Glycine receptor

Explanation: ***5HT-1A receptor*** - The patient's presentation of generalized anxiety disorder, treated with an SSRI (sertraline) and an adjunctive medication that lacks anticonvulsant or muscle relaxant properties, points to **buspirone**. - **Buspirone** is a 5HT-1A partial agonist, commonly used as an augmenting agent in anxiety disorders, which explains the mechanism of action. *Beta adrenergic receptor* - Medications acting on **beta-adrenergic receptors** (e.g., propranolol) are typically used for situational anxiety or performance anxiety, not generalized anxiety disorder, and they primarily reduce physical symptoms like palpitations and tremors. - While beta-blockers lack anticonvulsant or muscle relaxant properties, they are not typically considered a first-line adjunctive therapy for generalized anxiety after an SSRI failure. *GABA receptor* - Drugs acting on **GABA receptors** (e.g., benzodiazepines) are known for their anxiolytic, sedative, anticonvulsant, and muscle relaxant properties. - The question explicitly states that the adjunctive medication "notably lacks any anticonvulsant or muscle relaxant properties," ruling out GABAergic drugs. *Alpha adrenergic receptor* - Medications targeting **alpha-adrenergic receptors** (e.g., clonidine) are sometimes used for anxiety associated with opiate withdrawal or PTSD, but are not a common adjunctive treatment for generalized anxiety disorder in this context. - While they may lack anticonvulsant or muscle relaxant properties, their primary mechanism involves regulating sympathetic outflow rather than the specific mood and cognitive symptoms of GAD. *Glycine receptor* - The **glycine receptor** is an inhibitory ion channel, primarily found in the spinal cord and brainstem, involved in motor control and pain processing. - Agonists of this receptor are not commonly used to treat anxiety disorders, and the described clinical scenario does not align with its therapeutic applications.

Question 121: A 5-year-old girl is brought to the physician for evaluation of a pruritic rash on her face and extremities for the last year that increases with sun exposure. Her parents report that she often seems clumsy and has had several falls in the last two weeks. Physical examination shows an erythematous, scaly rash with hyperpigmentation over the nasal bridge and cheeks as well as on the dorsal forearms and hands. Urinalysis shows high levels of neutral amino acids. The most appropriate treatment for this patient's condition includes administration of an agent that is associated with which of the following adverse effects?

A. Irreversible retinopathy
B. Pseudotumor cerebri
C. Facial flushing (Correct Answer)
D. Calcium oxalate kidney stones
E. Nephrocalcinosis

Explanation: ***Facial flushing*** - This patient's constellation of symptoms, including a photosensitive rash, ataxia, and excessive urinary excretion of neutral amino acids, is characteristic of **Hartnup disease**. - Hartnup disease is treated with high-dose **niacin (vitamin B3)** supplementation, which can cause unpleasant but usually harmless facial flushing due to vasodilation. *Irreversible retinopathy* - This adverse effect is more commonly associated with chronic use of **hydroxychloroquine**, which is used in conditions like lupus or rheumatoid arthritis, not Hartnup disease. - While visual disturbances can occur with some vitamin deficiencies or toxicities, **niacin** does not typically cause irreversible retinopathy. *Pseudotumor cerebri* - **Pseudotumor cerebri** (idiopathic intracranial hypertension) is a known adverse effect of certain medications, such as **isotretinoin**, and can be exacerbated by excessive Vitamin A intake. - It is not a typical adverse effect associated with **niacin** supplementation used in Hartnup disease. *Calcium oxalate kidney stones* - **Calcium oxalate kidney stones** are associated with conditions causing hyperoxaluria, such as primary hyperoxaluria or malabsorption syndromes, but not typically with niacin supplementation. - While some vitamins can affect renal stone formation (e.g., high-dose vitamin C can increase oxalate), it's not a primary adverse effect of **niacin**. *Nephrocalcinosis* - **Nephrocalcinosis** involves calcium deposition in the renal parenchyma and is associated with conditions causing hypercalcemia or hypercalciuria (e.g., hyperparathyroidism, sarcoidosis, distal renal tubular acidosis). - It is not a common adverse effect of **niacin** therapy for Hartnup disease, which primarily involves malabsorption of specific amino acids.

Question 122: A 25-year-old man is brought to the emergency department by paramedics with a seizure lasting over 30 minutes. The patient's neighbors found him outside his apartment with all four limbs flailing and not responding to his name. No significant past medical history. On physical examination, the patient continues to be unresponsive and slightly cyanotic with irregular breathing. His teeth are clenched tightly. Intravenous glucose and an anticonvulsant medication are administered. Which of the following is the mechanism of action of the drug that was most likely administered to stop this patient’s seizure?

A. Blockage of voltage-gated calcium channels
B. Blockage of T-type calcium
C. Increase in frequency of chloride channel opening (Correct Answer)
D. Prolongation of chloride channel opening
E. Inactivation of sodium channels

Explanation: ***Increase in frequency of chloride channel opening*** - The patient is experiencing **status epilepticus** (seizure lasting >5 minutes or recurrent seizures without full recovery of consciousness), which requires rapid intervention, typically with a **benzodiazepine**. - **Benzodiazepines** (e.g., lorazepam, diazepam) act by binding to the **GABA-A receptor** and increasing the **frequency of chloride channel opening**, leading to neuronal hyperpolarization and reduced excitability. *Blockage of voltage-gated calcium channels* - This mechanism is characteristic of **gabapentin** and **pregabalin**, which are used for **neuropathic pain** and adjunctive seizure therapy, but not typically as first-line for status epilepticus. - Blocking voltage-gated calcium channels primarily reduces **neurotransmitter release**, which is a slower mechanism of action compared to GABAergic potentiation for acute seizure cessation. *Blockage of T-type calcium* - This is the primary mechanism of action for **ethosuximide**, which is used specifically for **absence seizures**. - Absence seizures are brief, generalized non-convulsive seizures, distinct from the generalized tonic-clonic seizure described in the patient. *Prolongation of chloride channel opening* - This mechanism is associated with **barbiturates** (e.g., phenobarbital), which also act on the GABA-A receptor but cause a **prolonged opening** of the chloride channel at high concentrations. - While barbiturates can be used for refractory status epilepticus, **benzodiazepines** are generally preferred as first-line due to a better safety profile and fewer side effects compared to barbiturates. *Inactivation of sodium channels* - This mechanism is characteristic of several anticonvulsant drugs, including **phenytoin, carbamazepine, and lamotrigine**. - These drugs are typically used for **long-term seizure control** and prevention, not as first-line agents for aborting an ongoing status epilepticus, due to their slower onset of action.

Question 123: A 23-year-old woman makes an appointment with a dermatologist for treatment of acne. As a result, she feels uncomfortable in public and feels as though everyone is looking at the pimples on her face. She cleans her face several times a day with face wash and avoids using make-up. She has tried many face creams and scar removal creams to help improve the condition of her skin, but nothing has worked. On examination, she has pustular acne on her cheeks and forehead. The physician prescribes an antibiotic along with isotretinoin. Which of the following drugs would you recommend in conjunction with isotretinoin?

A. Vitamin B6
B. Antihypertensives
C. Statins
D. Oral contraceptives (Correct Answer)
E. Folic acid

Explanation: ***Oral contraceptives*** - **Isotretinoin** is **highly teratogenic**, causing severe birth defects, so effective contraception is mandatory for females of childbearing potential. - **Oral contraceptives** are a common and effective method to prevent pregnancy during isotretinoin treatment. *Vitamin B6* - **Vitamin B6** (pyridoxine) is sometimes used for conditions like premenstrual syndrome or nausea, but it has **no direct role** in managing the side effects or enhancing the efficacy of isotretinoin. - While essential for various bodily functions, it is **not a recommended co-treatment** with isotretinoin for acne or its associated risks. *Antihypertensives* - **Antihypertensives** are used to treat **high blood pressure**, a condition not indicated in this patient's presentation or directly linked to isotretinoin use. - While isotretinoin can sometimes affect lipid profiles, it does **not typically cause hypertension** requiring this class of medication. *Statins* - **Statins** are prescribed to lower **cholesterol and triglyceride levels**, and while isotretinoin can cause **hyperlipidemia**, statins are generally not prescribed prophylactically. - **Monitoring lipid levels** is standard practice with isotretinoin, and statins would only be considered if elevations are significant and persistent. *Folic acid* - **Folic acid** supplementation is crucial during pregnancy to prevent neural tube defects but has **no direct interaction** or complementary role with isotretinoin for acne treatment. - While it's vital for women of childbearing age, it does **not address the immediate necessity for contraception** when taking isotretinoin.

Question 124: A 67-year-old man presents to his primary care physician primarily complaining of a tremor. He said that his symptoms began approximately 1 month ago, when his wife noticed his right hand making "abnormal movements" while watching television. His tremor worsens when he is distracted and improves with purposeful action, such as brushing his teeth or combing his hair. He reports having occasional headaches during times of stress. His wife notices he walks with "poor" posture and he finds himself having trouble staying asleep. He has a past medical history of migraine, generalized anxiety disorder, hypertension, and hyperlipidemia. On physical exam, the patient has a tremor that improves with extension of the arm. On gait testing, the patient has a stooped posture and takes short steps. Which of the following is the most effective treatment for this patient's symptoms?

A. Pramipexole
B. Carbidopa-levodopa (Correct Answer)
C. Trihexyphenidyl
D. Selegiline
E. Amantadine

Explanation: **Carbidopa-levodopa** - The patient's symptoms (resting tremor improving with purposeful action, stooped posture, short steps, sleep disturbances) are highly indicative of **Parkinson's disease**. **Carbidopa-levodopa** is the **most effective symptomatic treatment** for motor symptoms in Parkinson's, especially in older patients or those with significant functional impairment. - **Levodopa** is a precursor to dopamine and replaces deficient dopamine in the brain, while **carbidopa** prevents its peripheral breakdown, allowing more to reach the central nervous system and reducing side effects. *Pramipexole* - **Pramipexole** is a **dopamine agonist** which can be used, particularly in younger patients, to delay the need for levodopa, or as an adjunct. However, it is generally less effective than levodopa for severe motor symptoms. - Dopamine agonists have a higher incidence of side effects like **hallucinations, edema, and impulse control disorders** compared to levodopa, especially in older patients. *Trihexyphenidyl* - **Trihexyphenidyl** is an **anticholinergic drug** primarily used for **tremor-dominant Parkinson's disease**, particularly in younger patients. - It is generally contraindicated or used with extreme caution in older patients due to significant **anticholinergic side effects** such as confusion, memory impairment, and urinary retention, which would be problematic for a 67-year-old. *Selegiline* - **Selegiline** is a **MAO-B inhibitor** that slows the breakdown of dopamine in the brain. It can provide mild symptomatic benefit and may have neuroprotective properties. - While useful for mild symptoms or as an adjunct, it is generally **not as potent or effective** as levodopa for managing the significant motor symptoms described. *Amantadine* - **Amantadine** is an **antiviral agent** that has mild antiparkinsonian effects, thought to involve N-methyl-D-aspartate (NMDA) receptor antagonism and dopamine release. - It is often used for **mild symptoms** or specifically for **levodopa-induced dyskinesias**, but it is generally less effective than levodopa for primary motor symptoms.

Question 125: A 20-year-old college student presents to the emergency room complaining of insomnia for the past 48 hours. He explains that although his body feels tired, he is "full of energy and focus" after taking a certain drug an hour ago. He now wants to sleep because he is having hallucinations. His vital signs are T 100.0 F, HR 110 bpm, and BP of 150/120 mmHg. The patient states that he was recently diagnosed with "inattentiveness." Which of the following is the mechanism of action of the most likely drug causing the intoxication?

A. Blocks NMDA receptors
B. Activates mu opioid receptors
C. Displaces norepinephrine from secretory vesicles leading to norepinephrine depletion
D. Binds to cannabinoid receptors
E. Increases presynaptic dopamine and norepinephrine release from vesicles (Correct Answer)

Explanation: ***Increases presynaptic dopamine and norepinephrine releases from vesicles*** - The patient's presentation with **insomnia**, feeling "full of energy and focus," **hallucinations**, tachycardia (HR 110 bpm), and hypertension (BP 150/120 mmHg) after taking a drug, especially in the context of a recent diagnosis of "inattentiveness," strongly suggests **amphetamine intoxication**. Amphetamines are commonly prescribed for **ADHD**, and their mechanism involves increasing the release of **dopamine** and **norepinephrine** from presynaptic vesicles. - This increased release of **catecholamines** leads to the stimulant effects observed, including heightened energy, improved focus, and the adverse effects of agitation, psychosis (hallucinations), and sympathetic overdrive. *Blocks NMDA receptors* - Drugs that block **NMDA receptors**, such as **phencyclidine (PCP)** or **ketamine**, can cause dissociative and hallucinatory effects. - However, the patient's primary complaint of feeling "full of energy and focus" in the context of "inattentiveness" points more towards a classical stimulant rather than a dissociative anesthetic. *Activates mu opioid receptors* - Activating **mu opioid receptors** (e.g., by heroin, morphine, fentanyl) typically causes central nervous system **depression**, respiratory depression, miosis, and euphoria, not the stimulant and hyperactive state described. - The patient's symptoms of increased energy, focus, and elevated vital signs are the opposite of opioid effects. *Displaces norepinephrine from secretory vesicles leading to norepinephrine depletion* - This mechanism is characteristic of drugs like **reserpine**, which deplete catecholamines and lead to sedative or antihypertensive effects, not the stimulant and sympathomimetic presentation described. - Such a mechanism would cause a **decrease** in sympathetic activity, contrary to the patient's elevated heart rate and blood pressure. *Binds to cannabinoid receptors* - Binding to **cannabinoid receptors** (e.g., by marijuana) typically leads to effects such as euphoria, altered perception, impaired memory, and sometimes anxiety or paranoia. - While hallucinations can occur, the prominent "full of energy and focus" and significant sympathetic activation (tachycardia, hypertension) are not typical of cannabinoid intoxication.

Question 126: A scientist is studying a protein that is present on the plasma membrane of cells. He therefore purifies the protein in a lipid bilayer and subjects it to a number of conditions. His investigations show that the protein has the following properties: 1) It is able to change ion concentrations across the membrane without addition of ATP to the solution. 2) Its activity increases linearly with substrate concentration without any saturation even at mildly supraphysiologic conditions. 3) In some states the protein leads to an ion concentration change; whereas, it has no effect in other states. 4) Changing the electrical charge across the membrane does not affect whether the protein has activity. 5) Adding a small amount of an additional substance to the solution reliably increases the protein's activity. These findings are consistent with a protein with which of the following functions?

A. Maintenance of resting sodium and potassium concentrations
B. Transporting water in the collecting duct of the kidney
C. Reabsorption of glucose in the proximal kidney tubule
D. Mediating neuronal to muscle end plate communication (Correct Answer)
E. Causing depolarization during action potentials

Explanation: **Mediating neuronal to muscle end plate communication** - The properties described align with **ligand-gated ion channels**, which mediate communication at the neuromuscular junction. These channels open in response to a **neurotransmitter** (the "additional substance"), allowing ion flow without direct ATP hydrolysis. - The "some states" where it has no effect and "other states" where it leads to ion concentration change refer to its closed and open conformational states, dependent on ligand binding. The lack of saturation and independence from electrical charge are features of some channel kinetics. *Maintenance of resting sodium and potassium concentrations* - This function is primarily carried out by the **Na+/K+ ATPase pump**, which is an **active transporter** requiring ATP hydrolysis for its function, contradicting property (1). - The Na+/K+ ATPase transports ions against their concentration gradients and would be affected by changes in ATP availability. *Reabsorption of glucose in the proximal kidney tubule* - Glucose reabsorption primarily involves **Na+-glucose cotransporters (SGLTs)**, which are secondary active transporters. While they don't directly use ATP, their activity is linked to the Na+ gradient maintained by Na+/K+ ATPase, and they can show saturation kinetics. - SGLTs are symporters that move glucose and Na+ in the same direction and exhibit saturation at high glucose concentrations. *Transporting water in the collecting duct of the kidney* - Water transport in the collecting duct is mediated by **aquaporins**, which are passive water channels. Their activity is regulated by **vasopressin** (ADH), but they primarily transport water, not ions. - Aquaporins do not typically impact ion concentrations directly and their activity is usually quite specific to water movement. *Causing depolarization during action potentials* - Depolarization during action potentials is caused by the opening of **voltage-gated sodium channels**. These channels are directly affected by changes in **electrical charge** across the membrane, contradicting property (4). - Voltage-gated channels exhibit specific thresholds for activation and inactivation based on membrane potential.

Question 127: A 31-year-old man presents to his primary care physician endorsing three months of decreased sleep. He reports an inability to fall asleep; although once asleep, he generally sleeps through the night and wakes up at a desired time. He has instituted sleep hygiene measures, but this has not helped. He has not felt anxious or depressed and is otherwise healthy. You prescribe him a medication that has the potential side effect of priapism. From which of the following locations is the neurotransmitter affected by this medication released?

A. Locus ceruleus
B. Substantia nigra
C. Posterior pituitary
D. Raphe nucleus (Correct Answer)
E. Nucleus accumbens

Explanation: ***Raphe nucleus*** - The patient's symptoms of **insomnia** without anxiety or depression, despite good sleep hygiene, suggest a potential for prescribing **trazodone**. Trazodone is an antidepressant with **sedating properties** that acts as a serotonin receptor antagonist and reuptake inhibitor. - The **raphe nucleus** is the primary source of **serotonin** in the brain, and trazodone primarily affects serotonergic pathways, with priapism being a known but rare side effect associated with alpha-1 adrenergic blockade. *Locus ceruleus* - The **locus ceruleus** is the main source of **norepinephrine** in the brain, involved in arousal, attention, and stress responses. - While norepinephrine plays a role in sleep-wake cycles, it is not the primary neurotransmitter targeted by medications commonly associated with priapism for insomnia management in this context. *Substantia nigra* - The **substantia nigra** is a brain structure that produces **dopamine** and is primarily involved in motor control, with its degeneration leading to Parkinson's disease. - This region and its neurotransmitter are not typically associated with the treatment of insomnia or the specific side effect of priapism. *Posterior pituitary* - The **posterior pituitary** gland releases **oxytocin** and **vasopressin** (ADH), which are hormones synthesized in the hypothalamus. - This structure is part of the endocrine system and is not directly involved in the central nervous system pathways targeted by medications for insomnia with the potential for priapism. *Nucleus accumbens* - The **nucleus accumbens** is a key component of the **reward pathway** in the brain, primarily utilizing **dopamine** and involved in motivation, pleasure, and addiction. - While dopamine has some modulatory roles in sleep, it is not the primary target for effective insomnia treatment or associated with the specific side effects mentioned.

Question 128: An investigator is studying a local anesthetic that causes increased sympathetic activity. When given intravenously, it causes euphoria and pupillary dilation. Which of the following is the most likely effect of this drug at the synaptic cleft?

A. Increased release of norepinephrine
B. Decreased reuptake of norepinephrine (Correct Answer)
C. Decreased release of acetylcholine
D. Increased release of serotonin
E. Decreased breakdown of norepinephrine

Explanation: ***Decreased reuptake of norepinephrine*** - This drug causes **euphoria** and **pupillary dilation**, which are classic signs of increased **sympathetic nervous system** activity and **CNS stimulation**, consistent with enhanced **noradrenergic transmission**. - Decreasing the **reuptake of norepinephrine** would increase its concentration in the **synaptic cleft**, leading to more prolonged activation of **alpha and beta adrenergic receptors**. *Increased release of norepinephrine* - While increased release would also elevate **norepinephrine** in the **synaptic cleft**, reuptake inhibition is a more common mechanism for drugs producing similar effects like **cocaine** and **amphetamine-like stimulants**. - Without specific information, **reuptake inhibition** aligns better with the broad activation of **adrenergic receptors** and central effects described. *Decreased release of acetylcholine* - This would primarily affect **cholinergic systems**, and while some interactions exist, it does not directly explain the intense **adrenergic activation**, **euphoria**, and **pupillary dilation** observed. - **Acetylcholine** primarily mediates **parasympathetic responses** and **skeletal muscle contraction**, not the sympathetic effects seen here. *Increased release of serotonin* - Increased **serotonin** release is associated with hallucinogenic effects and mood modulation, but it does not directly lead to the pronounced **pupillary dilation** and widespread **alpha/beta adrenergic receptor activation** described. - The drug explicitly affects **adrenergic receptors**, making an effect on **norepinephrine** more direct. *Decreased breakdown of norepinephrine* - This mechanism, typically involving **MAO inhibitors**, would increase **norepinephrine** levels but is described as activating both **alpha and beta adrenergic receptors**, which points more towards a direct increase in synaptic availability rather than metabolic inhibition. - While it prolongs the action of **norepinephrine**, the primary mechanism described for such a general stimulant often involves **reuptake inhibition** or **enhanced release**.

Question 129: A 57-year-old man has worsening suprapubic discomfort 36 hours after undergoing a hemorrhoidectomy under spinal anesthesia. He reports that he has not urinated since the procedure. Examination shows a palpable bladder 4 cm above the symphysis pubis. He is treated with a drug that directly increases detrusor muscle tone. This patient is at increased risk for which of the following adverse effects of his treatment?

A. Mydriasis
B. Diaphoresis (Correct Answer)
C. Muscle spasms
D. Tachycardia
E. Constipation

Explanation: ***Diaphoresis*** - The patient has **postoperative urinary retention** and is likely treated with a **cholinergic agonist** (e.g., bethanechol) to increase detrusor muscle tone. - Cholinergic agonists stimulate **muscarinic receptors**, leading to increased **sweating (diaphoresis)** as a common adverse effect due to activation of muscarinic receptors on sweat glands. *Mydriasis* - **Mydriasis** (pupil dilation) is caused by **adrenergic stimulation** or **muscarinic antagonism**, not cholinergic agonism. - Cholinergic agonists generally cause **miosis** (pupil constriction). *Muscle spasms* - While high doses of cholinergic agonists can, in rare cases, lead to muscle fasciculations due to **nicotinic receptor overstimulation**, generalized **muscle spasms** are not a typical or direct adverse effect of the therapeutic doses used for bladder dysfunction. *Tachycardia* - Cholinergic agonists typically cause **bradycardia** due to their effect on the **sinoatrial (SA) node**, not tachycardia. - Tachycardia is usually associated with **sympathetic activation**. *Constipation* - Cholinergic agonists stimulate **gastrointestinal motility**, leading to increased peristalsis and potentially **diarrhea**, not constipation. - **Constipation** is a common side effect of **anticholinergic drugs**.

Question 130: A 3-year-old girl swallowed a handful of pills after her grandmother dropped the bottle on the ground this afternoon. She presents to the ER in a very drowsy but agitated state. She is clutching her abdomen, as if in pain, her skin is dry and flushed, and she does not know her name or where she is. Her pupils are dilated. Her grandmother reports that she has not urinated in several hours. The grandmother's medical history is significant for allergic rhinitis and osteoarthritis, both of which are treated with over the counter medications. What is the appropriate treatment for this child?

A. N-acetylcysteine
B. Naloxone
C. Physostigmine (Correct Answer)
D. Deferoxamine
E. Atropine

Explanation: ***Physostigmine*** is the correct answer. - The patient's presentation with **dry, flushed skin**, **dilated pupils**, agitation, drowsiness, abdominal pain, and urinary retention is highly suggestive of **anticholinergic toxicity**. - **Physostigmine** is a **cholinesterase inhibitor** that increases acetylcholine levels, directly reversing the effects of anticholinergic poisoning. *N-acetylcysteine* - **N-acetylcysteine** is the specific antidote for **acetaminophen overdose**, which is not indicated by the patient's symptoms. - The symptoms described do not match the typical presentation of acetaminophen toxicity (e.g., hepatic damage). *Naloxone* - **Naloxone** is used to reverse **opioid overdose**, which typically presents with respiratory depression and miosis (pinpoint pupils), contrary to this patient's dilated pupils and lack of respiratory compromise. - The clinical picture does not suggest opioid intoxication. *Deferoxamine* - **Deferoxamine** is a chelating agent used to treat **iron overdose**, which can cause gastrointestinal symptoms but does not typically present with the anticholinergic signs seen here. - There are no indications of iron toxicity in the patient's history or symptoms. *Atropine* - **Atropine** is an **anticholinergic agent** itself and would worsen the patient's symptoms by further blocking acetylcholine receptors. - It is used to treat cholinergic crises, not overdose of anticholinergic drugs.

Question 131: A 25-year-old man is brought to the emergency department by the police after a motor vehicle accident. He was reportedly speeding in a residential area and collided with a tree. He was later found by police naked in the street, screaming "shoot me so the devil will leave". A review of his medical record is unremarkable. At the hospital, he continues to act agitated and bizarre. His temperature is 37.0°C (98.6°F), the blood pressure is 140/86 mm Hg, and the heart rate is 90/min. The physical exam is notable for agitation, pacing around the room, occasionally yelling at the staff to help him "kill the devil". An ocular exam is significant for mild horizontal nystagmus. The patient appears to be drooling and has some difficulty with coordination. Which of the following is the most likely cause of this patient's presentation?

A. Central nervous system infection
B. Serotonin syndrome
C. Phencyclidine (PCP) intoxication (Correct Answer)
D. Metabolic abnormality
E. Cocaine intoxication

Explanation: ***Phencyclidine (PCP) intoxication*** - The patient's presentation with extreme **agitation**, **bizarre behavior** (running naked, screaming about the devil), **aggression**, **nystagmus** (often horizontal or vertical), drooling, and impaired coordination is highly characteristic of PCP intoxication. - PCP can induce **psychotic symptoms** very similar to schizophrenia, along with stimulant-like effects and cerebellar signs, all observed in this case. *Central nervous system infection* - While CNS infections can cause altered mental status and agitation, they typically present with fever, neck stiffness, or focal neurological deficits, which are absent here. - The specific combination of prominent **psychosis, nystagmus, and drooling** is not typical for most CNS infections. *Serotonin syndrome* - Serotonin syndrome involves altered mental status, **autonomic hyperactivity** (fever, tachycardia, hypertension), and neuromuscular abnormalities (hyperreflexia, clonus, rigidity). - While some features overlap, the prominent **psychotic delusions** and **nystagmus** without significant hyperthermia or muscle rigidity make it less likely. *Metabolic abnormality* - Severe metabolic abnormalities (e.g., hypoglycemia, hepatic encephalopathy, uremia) can cause altered mental status and agitation. - However, they rarely present with the specific combination of **psychotic features**, **nystagmus**, and **hyper-agitation** seen here without other clear systemic signs. *Cocaine intoxication* - Cocaine intoxication typically causes **euphoria**, **agitation**, **tachycardia**, and hypertension due to its stimulant effects. - While it can cause paranoia and psychosis, **prominent nystagmus**, drooling, and severe motor incoordination are less characteristic of cocaine than PCP.

Question 132: An investigator is studying the mechanism regulating pigment production in the skin. She has isolated a hormone produced by the anterior and intermediate lobe of the pituitary gland that stimulates neural crest-derived cells to produce pigments through the oxidation and polymerization of the amino acid tyrosine. This hormone is most likely cosecreted with a substance that acts on which of the following receptors?

A. TSH receptor
B. Glucocorticoid receptor
C. Vasopressin receptor
D. Dopamine receptor
E. Mu receptor (Correct Answer)

Explanation: ***Mu receptor*** - The hormone described, which stimulates pigment production in neural crest-derived cells, is **melanocyte-stimulating hormone (MSH)**. - **MSH** is derived from the pro-opiomelanocortin (POMC) precursor, which also gives rise to **β-endorphin**, a potent opioid peptide that acts on **mu opioid receptors**. *TSH receptor* - The **TSH receptor** binds thyroid-stimulating hormone (TSH), which primarily regulates thyroid hormone production and is not directly related to pigment production or opioid co-secretion from POMC. - TSH is produced by the anterior pituitary but from a different lineage than POMC-derived hormones. *Glucocorticoid receptor* - The **glucocorticoid receptor** binds cortisol and other glucocorticoids, which are involved in stress response and metabolism. - While ACTH (also derived from POMC) can stimulate adrenal glucocorticoid release, the question specifically refers to a substance *cosecreted* with MSH, not one that is *regulated* by MSH or its derivatives. *Vasopressin receptor* - **Vasopressin receptors** bind antidiuretic hormone (ADH), which regulates water balance and blood pressure. - ADH is produced by the posterior pituitary (though synthesized in the hypothalamus) and is not cosecreted with MSH from the anterior/intermediate pituitary. *Dopamine receptor* - **Dopamine receptors** bind dopamine, a neurotransmitter involved in various functions, including the inhibition of prolactin release from the pituitary. - While dopamine can influence pituitary function, it is not cosecreted with MSH in the manner described, nor is it a direct product of POMC cleavage.

Question 133: A 45-year-old unconscious man is brought to the emergency department by a friend who witnessed him collapse. They were working in a greenhouse spraying the vegetables when the man started to complain of blurred vision and nausea. On the way to the hospital, the man lost consciousness and lost bladder continence. The patient’s vital signs are as follows: blood pressure 95/60 mm Hg; heart rate 59/min; respiratory rate 22/min; and temperature 36.0℃ (96.8℉). On examination, he is unconscious with a GCS score of 7. His pupils are contracted and react poorly to light. Lung auscultation reveals diffuse wheezing. Cardiac auscultation is significant for bradycardia. Abdominal auscultation reveals increased bowel sounds. A cardiac monitor shows bradycardia with grade 2 AV-block. Which of the following leads to the cardiac manifestations seen in this patient?

A. Activation of M1-cholinergic receptors
B. Activation of β2-adrenergic receptors
C. Activation of M2-cholinergic receptors (Correct Answer)
D. Inhibition of β1-adrenergic receptors
E. Inhibition of M2-cholinergic receptors

Explanation: ***Activation of M2-cholinergic receptors*** - The patient's symptoms (blurred vision, nausea, unconsciousness, incontinence, miosis, wheezing, bradycardia, increased bowel sounds) are classic for **organophosphate poisoning**, which involves excessive activation of the **parasympathetic nervous system**. - **M2 receptors** are primarily located in the heart and, when activated by acetylcholine, lead to slowed heart rate (bradycardia) and decreased conduction (AV block), characteristic of the cardiac manifestations observed. *Activation of M1-cholinergic receptors* - **M1 receptors** are primarily found in neural tissue and glands, contributing to increased GI motility and glandular secretions but not directly to cardiac slowing. - Their activation does not directly cause the observed **bradycardia** and **AV block**. *Activation of β2-adrenergic receptors* - **β2-adrenergic receptors** are part of the sympathetic nervous system and are present in the smooth muscle of the bronchioles and blood vessels. - Their activation typically causes **bronchodilation** and **vasodilation**, which would counteract the patient's wheezing and hypotension, and are not involved in bradycardia. *Inhibition of β1-adrenergic receptors* - **β1-adrenergic receptors** are found in the heart and their inhibition would lead to bradycardia, but organophosphate poisoning causes **cholinergic excess**, not adrenergic inhibition. - This mechanism would not explain the other widespread **parasympathetic activation** symptoms like miosis, wheezing, and increased GI motility. *Inhibition of M2-cholinergic receptors* - **Inhibition of M2-cholinergic receptors** would lead to an increase in heart rate and improved AV conduction, rather than the severe **bradycardia** and **AV block** observed. - This mechanism is characteristic of **anticholinergic toxidrome**, which presents with opposing symptoms.

Question 134: A 30-year-old woman is undergoing work up for progressive weakness. She reports that at the end of the work day, her "eyelids droop" and her "eyes cross," but in the morning she feels "ok." She reports that her legs feel heavy when she climbs the stairs of her house to go to sleep at night. As part of her work up, the physician has her hold her gaze toward the ceiling, and after a minute, her lids become ptotic. She is given an IV medication and her symptoms resolve, but return 10 minutes later. Which of the following medications was used in the diagnostic test performed for this patient?

A. Neostigmine
B. Pyridostigmine
C. Physostigmine
D. Edrophonium (Correct Answer)
E. Echothiophate

Explanation: ***Edrophonium*** * The clinical picture strongly suggests **myasthenia gravis**, characterized by fluctuating muscle weakness that worsens with activity and improves with rest, exemplified by the patient's symptoms at the end of the day. * **Edrophonium** is an **ultrashort-acting acetylcholinesterase inhibitor** used in the **Tensilon test** to diagnose myasthenia gravis. Its rapid onset and brief duration of action (symptoms resolve briefly then return) match the scenario described. *Neostigmine* * While **neostigmine** is an acetylcholinesterase inhibitor, it has a **longer duration of action** compared to edrophonium and is typically used for the *treatment* of myasthenia gravis, not primarily for the rapid diagnostic test. * It is also used to reverse the effects of non-depolarizing neuromuscular blockers. *Pyridostigmine* * **Pyridostigmine** is a commonly used, **intermediate-acting acetylcholinesterase inhibitor** used for the *chronic management* of myasthenia gravis due to its longer duration (3-6 hours). * It would not produce the rapid, transient improvement and return of symptoms seen in the diagnostic test described. *Physostigmine* * **Physostigmine** is an acetylcholinesterase inhibitor that can cross the **blood-brain barrier** and is primarily used to treat central anticholinergic toxicity. * It is not used for the diagnosis of myasthenia gravis due to its central effects and different clinical indications. *Echothiophate* * **Echothiophate** is an **irreversible acetylcholinesterase inhibitor** used topically for glaucoma. * Its irreversible nature and long duration of action make it unsuitable for a diagnostic test like the one described, as the effects would not resolve quickly.

Question 135: A 42-year-old homeless man is brought to the emergency room after he was found unconscious in a park. He has alcohol on his breath and is known to have a history of chronic alcoholism. A noncontrast CT scan of the head is normal. The patient is treated for acute alcohol intoxication and admitted to the hospital. The next day, the patient demands to be released. His vital signs are a pulse 120/min, a respiratory rate 22/min, and blood pressure 136/88 mm Hg. On physical examination, the patient is confused, agitated, and sweating profusely, particularly from his palms. Generalized pallor is present. What is the mechanism of action of the drug recommended to treat this patient’s most likely condition?

A. It decreases the duration of GABA-gated chloride channel opening.
B. It increases the duration of GABA-gated chloride channel opening.
C. It activates the GABA receptors by binding at the GABA binding site.
D. It decreases the frequency of GABA-gated chloride channel opening.
E. It increases the frequency of GABA-gated chloride channel opening. (Correct Answer)

Explanation: ***It increases the frequency of GABA-gated chloride channel opening.*** - The patient's symptoms (agitation, confusion, sweating, tachycardia, elevated blood pressure) 24 hours after acute alcohol intoxication, in a chronic alcoholic, are highly suggestive of **alcohol withdrawal syndrome**, likely progressing towards **delirium tremens**. - **Benzodiazepines** are the first-line treatment for alcohol withdrawal. They act by **increasing the frequency of GABA-gated chloride channel opening**, leading to increased chloride influx, hyperpolarization, and reduced neuronal excitability, thus counteracting the CNS hyperexcitability of alcohol withdrawal. *It decreases the duration of GABA-gated chloride channel opening.* - Some drugs, like certain **antiepileptics** (e.g., lamotrigine), can modulate GABA indirectly or affect other ion channels, but this is not the primary mechanism of action for benzodiazepines. - Decreasing the duration of GABA-gated chloride channel opening would further contribute to neuronal excitation, worsening the alcohol withdrawal symptoms. *It increases the duration of GABA-gated chloride channel opening.* - This mechanism is characteristic of **barbiturates**, not benzodiazepines. While barbiturates can also be used for severe alcohol withdrawal, benzodiazepines are generally preferred due to a wider therapeutic index and lower risk of respiratory depression. - Barbiturates have a higher potential for sedation and overdose than benzodiazepines. *It activates the GABA receptors by binding at the GABA binding site.* - **GABA itself** binds to the GABA binding site on the receptor. Benzodiazepines are **allosteric modulators**; they bind to a different site on the GABA-A receptor, not the GABA binding site. - Direct activation of the GABA binding site by an exogenous substance is not the primary mechanism of action of drugs used for alcohol withdrawal. *It decreases the frequency of GABA-gated chloride channel opening.* - Decreasing the frequency of GABA-gated chloride channel opening would lead to reduced inhibitory signaling and increased neuronal excitability, which would exacerbate the symptoms of alcohol withdrawal. - This mechanism is not associated with drugs used to treat alcohol withdrawal.

Question 136: A 26-year-old man is brought to the hospital by his wife who complains that her husband has been behaving oddly for the past few hours. The patient’s wife says that she has known him for only 4 months. The wife is unable to give any past medical history. The patient’s speech is difficult to follow, and he seems very distracted. After 15 minutes, he becomes agitated and starts to bang his head on a nearby pillar. He is admitted to the psychiatric ward and is given an emergency medication, after which he calms down. In the next 2 days, he continues to become agitated at times and required 2 more doses of the same drug. On the 4th day of admission, he appears very weak, confused, and does not respond to questions appropriately. His vital signs include: temperature 40.0°C (104.0°F), blood pressure 160/95 mm Hg, and pulse 114/min. On physical examination, he is profusely diaphoretic. He is unable to stand upright or even get up from his bed. Which of the following is the mechanism of action of the drug which most likely caused this patient’s current condition?

A. Skeletal muscle relaxation
B. Agonistic effect on dopamine receptors
C. Serotonin reuptake inhibition
D. Histamine H2 receptor blocking
E. Dopamine receptor blocking (Correct Answer)

Explanation: ***Dopamine receptor blocking*** - The patient's presentation with **fever, altered mental status, muscle rigidity**, and **autonomic instability** (tachycardia, hypertension, diaphoresis) after receiving antipsychotic medication strongly suggests **neuroleptic malignant syndrome (NMS)**. - NMS is caused by a severe decrease in **dopaminergic activity**, primarily due to the blockade of **D2 dopamine receptors** in the basal ganglia and hypothalamus by antipsychotics. - The classic tetrad of NMS includes: **hyperthermia, muscle rigidity, altered mental status**, and **autonomic instability**. *Skeletal muscle relaxation* - While agitation might be treated with benzodiazepines, which cause muscle relaxation, this mechanism does not explain the **severe rigidity, hyperthermia**, and **autonomic dysfunction** seen in the patient. - **Muscle rigidity** (lead-pipe rigidity) is a hallmark of the patient's current condition, contradicting the idea of muscle relaxation. *Agonistic effect on dopamine receptors* - An agonistic effect on dopamine receptors would typically lead to symptoms similar to **psychosis** or **mania**, not the severe rigidity and hypodopaminergic state observed in NMS. - This mechanism would counteract the effects of antipsychotics and would not cause NMS. *Serotonin reuptake inhibition* - This is the mechanism of action for **SSRIs**, and an excess of serotonin can lead to **serotonin syndrome**, which shares some features with NMS but typically includes **hyperreflexia** and **myoclonus**, rather than lead-pipe rigidity. - The context of treating acute psychosis with an emergency medication points more towards an antipsychotic, not an antidepressant. *Histamine H2 receptor blocking* - **Histamine H2 receptor blockers** are used to treat conditions like **acid reflux** and **peptic ulcers**; they have no direct neurological effects that would cause NMS. - This mechanism is entirely irrelevant to the patient's psychiatric symptoms and subsequent severe adverse reaction.

Question 137: A 24-year-old woman delivers a girl by normal vaginal delivery, Apgar scores are 8 and 9 at 1 and 5 minutes respectively. The newborn’s vitals are normal. On examination, the attending pediatrician finds a circular skin defect that measures 0.5 cm in diameter. The defect is hairless and extends into the dermis. The delivery was atraumatic and there were no surgical instruments in the area. The pediatric team believes this is a congenital defect. The remaining examination is normal. The mother gives past history of having constant diarrhea for 3 months about 2 years ago, weight loss of 5 kg (11 lb) in 3 months, palpitations, and sensitivity to heat. She visited a community hospital and was prescribed a medication for this problem. She did not visit the hospital for any of her routine check-ups and continued taking her medications. Which drug can predispose the newborn to this condition?

A. Propylthiouracil
B. Octreotide
C. Propranolol
D. Levothyroxine
E. Methimazole (Correct Answer)

Explanation: - ***Methimazole*** - The congenital defect described is **aplasia cutis congenita**, a rare **skin defect** characterized by the absence of some or all layers of skin, most commonly found on the scalp. - Exposure to **methimazole** during pregnancy, particularly in the first trimester, is associated with an increased risk of aplasia cutis congenita. The mother's history of hyperthyroidism (diarrhea, weight loss, palpitations, heat sensitivity) and subsequent medication use points to an antithyroid drug like methimazole. - *Propylthiouracil* - While **propylthiouracil (PTU)** is also an antithyroid drug, it is generally considered the **preferred treatment for hyperthyroidism during the first trimester of pregnancy** due to a lower risk of teratogenic effects compared to methimazole. - Although PTU can cause various birth defects, it is **not specifically associated with aplasia cutis congenita** in the same way methimazole is. - *Octreotide* - **Octreotide** is a synthetic analog of **somatostatin** used to treat conditions like acromegaly, neuroendocrine tumors, and variceal bleeding. - There is **no known association** between octreotide exposure during pregnancy and aplasia cutis congenita. - *Propranolol* - **Propranolol** is a **beta-blocker** often used to manage symptoms of hyperthyroidism (e.g., palpitations, tremors) but does not treat the underlying thyroid dysfunction. - While beta-blockers can have some effects on the fetus, such as **intrauterine growth restriction (IUGR)** or **bradycardia**, they are not linked to aplasia cutis congenita. - *Levothyroxine* - **Levothyroxine** is a synthetic **thyroid hormone** used to treat hypothyroidism, not hyperthyroidism. - Taking levothyroxine during pregnancy is generally safe and necessary for women with hypothyroidism to ensure proper fetal development; it is **not associated with congenital skin defects**.

Question 138: A 35-year-old female presents to her primary care physician because of chronic fatigue that has stopped her from gardening and walking with her friends. Upon further questioning, she elaborates that she feels fine after waking up but gradually becomes more tired and weak as the day progresses. This appears to be particularly problematic when she is engaged in physical activity or when eating. Review of systems elicits that she occasionally experiences double vision after spending a prolonged period looking at a computer screen. Testing confirms the diagnosis and the patient is prescribed a long-acting medication to alleviate her symptoms. The products of the enzyme that is inhibited by the prescribed drug are transported by a protein that is sensitive to which of the following chemicals?

A. Guanethidine
B. Hemicholinium (Correct Answer)
C. Vesamicol
D. Botulinum
E. Reserpine

Explanation: ***Hemicholinium*** - The clinical presentation of **fatigue worsening with activity and throughout the day**, along with **double vision**, is highly suggestive of **myasthenia gravis**. - **Pyridostigmine**, a long-acting **acetylcholinesterase inhibitor**, is used to treat myasthenia gravis, increasing acetylcholine at the neuromuscular junction for improved muscle strength. The question asks about the transport of the products of the enzyme inhibited by Pyridostigmine. Acetylcholinesterase breaks down acetylcholine into choline and acetate. Hence, it is asking about **choline transport**. **Hemicholinium** is a drug that inhibits the high-affinity reuptake of choline into the presynaptic neuron, disrupting acetylcholine synthesis. *Guanethidine* - **Guanethidine** is a **sympathetic neuron blocker** that inhibits the release of norepinephrine from adrenergic nerve terminals. - It does not directly affect acetylcholine synthesis or transport, which is the focus of the question. *Vesamicol* - **Vesamicol** blocks the **vesicular acetylcholine transporter (VAChT)**, preventing acetylcholine from being packaged into synaptic vesicles. - While it affects acetylcholine storage, it does not directly inhibit choline reuptake, which is the specific mechanism relevant to the question. *Botulinum* - **Botulinum toxin** prevents the release of acetylcholine from presynaptic terminals by cleaving SNARE proteins, leading to muscle paralysis. - Its action is on **acetylcholine release**, not on the transport of its precursor (choline) or breakdown products. *Reserpine* - **Reserpine** depletes **monoamine neurotransmitters** (norepinephrine, dopamine, serotonin) by inhibiting their uptake into storage vesicles. - It is primarily associated with adrenergic and serotonergic pathways, not cholinergic transmission.

Question 139: A 23-year-old man is brought to the emergency department from a college party because of a 1-hour history of a crawling sensation under his skin. He appears anxious and is markedly pale. His temperature is 38°C (100.4°F), pulse is 104/min, respirations are 18/min, and blood pressure is 145/90 mm Hg. Physical examination shows diaphoretic skin, moist mucous membranes, and dilated pupils. Which of the following substances is most likely the cause of this patient's symptoms?

A. Scopolamine
B. Phencyclidine
C. Cocaine (Correct Answer)
D. Oxycodone
E. Lysergic acid diethylamide

Explanation: ***Cocaine*** - The patient's symptoms of **anxiety**, **diaphoresis**, **mydriasis (dilated pupils)**, and **tachycardia** are consistent with **sympathomimetic toxicity**, commonly seen with cocaine use. - The **crawling sensation under the skin (formication)**, also known as "cocaine bugs," is a classic symptom of significant cocaine intoxication. *Scopolamine* - Scopolamine is an **anticholinergic** agent, causing symptoms like **dry mouth**, **dilated pupils**, and **tachycardia**, but typically also causes dry skin and urinary retention. - It would not usually present with diaphoresis or the specific crawling sensation. *Phencyclidine* - **Phencyclidine (PCP)** intoxication characteristically causes **nystagmus**, **ataxia**, and often leads to **violent behavior** or **agitation**, which are not the primary features described here. - While it can cause hallucinations and psychosis, the "crawling sensation" is less typical for PCP compared to cocaine. *Oxycodone* - **Oxycodone** is an **opioid**, which would typically cause **miosis (constricted pupils)**, **respiratory depression**, and **sedation**, directly contradicting the patient's symptoms. - It would not lead to anxiety, tachycardia, or diaphoresis in the manner described. *Lysergic acid diethylamide* - **Lysergic acid diethylamide (LSD)** is a **hallucinogen** known for causing marked perceptual distortions, vivid hallucinations, and altered thought processes. - While it can cause autonomic symptoms like sweating and tachycardia, the specific "crawling sensation" is not a hallmark symptom of LSD, and the clinical picture is more suggestive of sympathomimetic overload.

Question 140: A 22-year-old man is brought to the emergency department 10 minutes after falling down a flight of stairs. An x-ray of the right wrist shows a distal radius fracture. A rapidly acting intravenous anesthetic agent is administered, and closed reduction of the fracture is performed. Following the procedure, the patient reports palpitations and says that he experienced an “extremely vivid dream,” in which he felt disconnected from himself and his surroundings while under anesthesia. His pulse is 110/min and blood pressure is 140/90 mm Hg. The patient was most likely administered a drug that predominantly blocks the effects of which of the following neurotransmitters?

A. Endorphin
B. Dopamine
C. Norepinephrine
D. Glutamate (Correct Answer)
E. Gamma-aminobutyric acid

Explanation: ***Glutamate*** - The patient's symptoms of **dissociative anesthesia**, **vivid dreams**, and **palpitations** are characteristic of **ketamine**, which is a rapidly acting intravenous anesthetic. - Ketamine works primarily as a **non-competitive antagonist of the NMDA receptor**, blocking the excitatory effects of glutamate. *Endorphin* - Endorphins are **endogenous opioid peptides** that act on opioid receptors, producing analgesia and euphoria. - Drugs acting predominantly on endorphin pathways (e.g., opioids) do not typically cause dissociative states or vivid dreams as described. *Dopamine* - Dopamine is involved in reward, motivation, and motor control; drugs affecting dopamine (e.g., antipsychotics, Parkinson's medications) have different primary effects. - Blocking dopamine would not directly produce dissociative anesthesia or the cardiovascular and hallucinatory side effects seen with ketamine. *Norepinephrine* - Norepinephrine is a neurotransmitter involved in the **sympathetic nervous system** and its effects on alertness, vigilance, and the fight-or-flight response. - While ketamine can cause sympathetic stimulation leading to increased heart rate and blood pressure, its primary mechanism of anesthesia is not through norepinephrine blockade. *Gamma-aminobutyric acid* - **Gamma-aminobutyric acid (GABA)** is the main inhibitory neurotransmitter in the CNS, and drugs that enhance GABAergic activity (e.g., benzodiazepines, propofol) typically cause sedation, anxiolysis, and amnesia. - This patient's symptoms of vivid dreams and dissociation are opposite to the effects of GABAergic anesthetics, which often produce unconsciousness without such mental experiences.

Question 141: A 19-year-old man is seen by his primary care physician. The patient has a history of excessive daytime sleepiness going back several years. He has begun experiencing episodes in which his knees become weak and he drops to the floor when he laughs. He has a history of marijuana use. His family history is notable for hypertension and cardiac disease. His primary care physician refers him for a sleep study, which confirms your suspected diagnosis. Which of the following is the best first-line pharmacological treatment for this patient?

A. Zolpidem
B. Lisdexamfetamine
C. Modafinil (Correct Answer)
D. Methylphenidate
E. Dextroamphetamine

Explanation: ***Modafinil*** - This patient presents with symptoms of **narcolepsy** (excessive daytime sleepiness, cataplexy triggered by laughter). **Modafinil** is a non-amphetamine stimulant and a **first-line treatment** for the **excessive daytime sleepiness** component of narcolepsy due to its efficacy in improving wakefulness with a relatively low side effect profile. - It works by increasing the release of **monoamines (norepinephrine, dopamine, serotonin)** and histamine, promoting wakefulness without significant cardiovascular effects or abuse potential compared to traditional stimulants. - **Note:** While modafinil addresses the daytime sleepiness, **cataplexy** would typically require additional treatment with **sodium oxybate** (first-line for cataplexy) or antidepressants (SSRIs, SNRIs, or TCAs). *Zolpidem* - **Zolpidem** is a **sedative-hypnotic** primarily used for the short-term treatment of **insomnia**, not for excessive daytime sleepiness or narcolepsy. - Administering a sedative would worsen the patient's primary complaint of daytime sleepiness. *Lisdexamfetamine* - **Lisdexamfetamine** is a **prodrug of dextroamphetamine**, a potent central nervous system stimulant used for **ADHD** and sometimes narcolepsy. - While effective, it is generally considered a **second-line treatment** for narcolepsy after non-amphetamine stimulants like modafinil, especially given its higher potential for abuse and side effects. *Methylphenidate* - **Methylphenidate** is a **central nervous system stimulant** commonly used for **ADHD** and, in some cases, narcolepsy. - Similar to lisdexamfetamine, it is a stronger stimulant with greater potential for side effects and abuse compared to modafinil, making it a less preferred first-line option. *Dextroamphetamine* - **Dextroamphetamine** is a potent **amphetamine stimulant** effective for increasing wakefulness in narcolepsy. - However, due to its **higher abuse potential**, cardiovascular side effects, and more significant impact on dopamine pathways, it is usually reserved for cases refractory to safer options like modafinil.

Question 142: A 58-year-old man comes to the physician for a 2-month history of increased urinary frequency. Urodynamic testing shows a urinary flow rate of 11 mL/s (N>15) and a postvoid residual volume of 65 mL (N<50). Prostate-specific antigen level is 3.2 ng/mL (N<4). Treatment with a drug that also increases scalp hair regrowth is initiated. Which of the following is the most likely mechanism of action of this drug?

A. Gonadotropin-releasing hormone receptor agonism
B. Decreased conversion of hydroxyprogesterone to androstenedione
C. Decreased conversion of testosterone to dihydrotestosterone (Correct Answer)
D. Decreased conversion of testosterone to estradiol
E. Selective alpha-1A/D receptor antagonism

Explanation: ***Decreased conversion of testosterone to dihydrotestosterone*** - The patient's symptoms (urinary frequency), urodynamic findings (low flow rate, elevated postvoid residual), and slightly elevated PSA are consistent with **benign prostatic hyperplasia (BPH)**. - A drug that treats BPH and also increases **scalp hair regrowth** is a **5α-reductase inhibitor** (e.g., finasteride), which works by blocking the conversion of testosterone to dihydrotestosterone (DHT), the primary androgen responsible for prostate growth and androgenetic alopecia. *Gonadotropin-releasing hormone receptor agonism* - GnRH agonists (e.g., leuprolide) are used for advanced **prostate cancer** by initially stimulating and then desensitizing GnRH receptors, leading to decreased testosterone production. - They do not promote scalp hair regrowth but can cause **testicular atrophy** and **hot flashes**. *Decreased conversion of hydroxyprogesterone to androstenedione* - This pathway is involved in the synthesis of androgens in the adrenal glands and gonads but is not the primary mechanism targeted by drugs used for BPH with hair regrowth benefits. - Drugs acting at this step are not typically associated with BPH treatment or hair regrowth. *Decreased conversion of testosterone to estradiol* - This refers to the action of **aromatase inhibitors** (e.g., anastrozole), which block the conversion of androgens to estrogens. - Aromatase inhibitors are used in the treatment of **hormone-sensitive breast cancer** and do not treat BPH or promote scalp hair regrowth. *Selective alpha-1A/D receptor antagonism* - **Alpha-1 blockers** (e.g., tamsulosin) relax the smooth muscle in the prostate and bladder neck, improving urinary flow in BPH. - While effective for BPH, they do not impact **hair regrowth** and may cause orthostatic hypotension or ejaculatory dysfunction.

Question 143: A 26-year-old woman presents with an 8-month history of insomnia and anxiety. She says that she has difficulty sleeping and has feelings of impending doom linked to her difficult financial situation. No significant family history and no current medications. The patient was prescribed an 8-week supply of medication. She follows up 4 weeks later saying that she has increased anxiety and needs a refill. She says that over the past month, due to increasing anxiety levels, she started taking extra doses of her medication to achieve an anxiolytic effect. Which of the following medications was most likely prescribed to this patient?

A. Triazolam (Correct Answer)
B. Hydroxyzine
C. Zolpidem
D. Buspirone
E. Propranolol

Explanation: ***Triazolam*** - Triazolam is a **short-acting benzodiazepine** commonly prescribed for insomnia, but its rapid onset and short duration can lead to **rebound anxiety** and dependence with chronic use, as seen with the patient's increased anxiety and need for a refill. - The patient's need to take "extra doses...to achieve an anxiolytic effect" suggests the development of **tolerance** and dependence, which is characteristic of benzodiazepine misuse. *Hydroxyzine* - Hydroxyzine is a **first-generation antihistamine** with sedative and anxiolytic properties, often used for anxiety and insomnia due to its relatively low abuse potential. - It does not typically cause the **rapid tolerance** and withdrawal symptoms (like increased anxiety needing extra doses) seen with benzodiazepines. *Zolpidem* - Zolpidem is a **non-benzodiazepine hypnotic** (Z-drug) that acts on GABA-A receptors and is commonly prescribed for insomnia. - While it has **lower dependence potential** than benzodiazepines, the patient's presentation with rapid tolerance development and dose escalation for anxiolytic effect is more characteristic of **benzodiazepine use** rather than zolpidem, which primarily provides sedation without strong anxiolytic effects. *Buspirone* - Buspirone is an **anxiolytic** that works on serotonin receptors and is used for generalized anxiety disorder, but it has a **delayed onset of action** (weeks) and lacks the immediate anxiolytic effect that would lead to acute dose escalation. - It has a **low potential for abuse** or dependence, making it an unlikely choice for a patient rapidly escalating doses for an immediate effect. *Propranolol* - Propranolol is a **beta-blocker** used to manage the physical symptoms of anxiety (e.g., tremors, palpitations), but it does not directly treat the psychological symptoms of anxiety or insomnia. - It is not associated with **tolerance, dependence**, or the need for dose escalation to achieve an anxiolytic effect.

Question 144: A 16-year-old boy is brought to the emergency department by ambulance with a visible deformity of the upper thigh after being involved in a motor vehicle collision. He is informed that he will require surgery and is asked about his medical history. He mentions that he had surgery to remove his tonsils several years ago and at that time suffered a complication during the surgery. Specifically, shortly after the surgery began, he began to experience severe muscle contractions and an increased body temperature. Based on this information, a different class of muscle relaxants are chosen for use during the upcoming surgery. If these agents needed to be reversed, the reversal agent should be administered with which of the following to prevent off-target effects?

A. Atropine (Correct Answer)
B. Epinephrine
C. Echothiophate
D. Methacholine
E. Phentolamine

Explanation: **Atropine** - The patient's history of **severe muscle contractions** and **increased body temperature** during prior surgery indicates **malignant hyperthermia**, a contraindication for succinylcholine - Therefore, **nondepolarizing neuromuscular blockers** will be used instead and reversal is typically achieved with **neostigmine** (acetylcholinesterase inhibitor) - Neostigmine increases acetylcholine at **both nicotinic and muscarinic receptors**, causing undesirable **muscarinic side effects** (bradycardia, salivation, bronchospasm, increased GI motility) - **Atropine** or **glycopyrrolate** (muscarinic antagonists) must be co-administered to prevent these off-target muscarinic effects *Epinephrine* - Sympathomimetic acting on **alpha- and beta-adrenergic receptors** used for anaphylaxis, severe asthma, and cardiac arrest - Not used to prevent muscarinic side effects of acetylcholinesterase inhibitors *Echothiophate* - **Irreversible acetylcholinesterase inhibitor** used for glaucoma treatment - Would exacerbate rather than prevent cholinergic side effects when combined with neostigmine *Methacholine* - **Muscarinic cholinergic agonist** used in bronchial challenge tests for asthma diagnosis - Would worsen muscarinic side effects rather than preventing them *Phentolamine* - **Alpha-adrenergic blocker** used for hypertensive crises from pheochromocytoma or vasopressor extravasation - No role in managing muscarinic side effects of acetylcholinesterase inhibitors

Question 145: A 43-year-old male with a history of thyroid cancer status post total thyroidectomy presents to his primary care physician after repeated bouts of headaches. His headaches are preceded by periods of anxiety, palpitations, and sweating. The patient says he is unable to pinpoint any precipitating factors and instead says the events occur without warning. Of note, the patient's father and uncle also have a history of thyroid cancer. On exam his vitals are: T 36.8 HR 87, BP 135/93, RR 14, and O2 Sat 100% on room air. The patient's TSH is within normal limits, and he reports taking his levothyroxine as prescribed. What is the next best step in diagnosing this patient's chief complaint?

A. 24-hour urine free cortisol
B. Plasma aldosterone/renin ratio
C. Abdominal CT scan with and without IV contrast
D. Plasma fractionated metanephrines (Correct Answer)
E. High dose dexamethasone suppression test

Explanation: ***Plasma fractionated metanephrines*** - The patient's symptoms of **anxiety, palpitations, sweating, and headaches** occurring in discrete "attacks" are classic for a **pheochromocytoma**, a tumor that secretes catecholamines. - Given the patient's and his family's history of **thyroid cancer**, specifically likely **medullary thyroid cancer** due to the familial link, there is a high suspicion for **Multiple Endocrine Neoplasia type 2 (MEN2)**, which commonly includes pheochromocytoma. **Plasma fractionated metanephrines** are the most sensitive screening test for pheochromocytoma. *24-hour urine free cortisol* - This test is used to detect **Cushing's syndrome**, which involves excessive cortisol production. - Although Cushing's can cause **hypertension**, the paroxysmal symptoms of anxiety, palpitations, and sweating are not typical of Cushing's syndrome. *Plasma aldosterone/renin ratio* - This ratio is used to screen for **primary hyperaldosteronism**, a cause of secondary hypertension. - While the patient has **hypertension (135/93 mm Hg)**, his symptom complex of episodic anxiety, palpitations, and sweating is not characteristic of primary hyperaldosteronism. *Abdominal CT scan with and without IV contrast* - An abdominal CT scan can visualize adrenal masses, but it is typically performed *after* biochemical confirmation of a pheochromocytoma to localize the tumor. - Performing imaging before biochemical testing risks incidentalomas or missing a biochemically active but small tumor, and it is not the most appropriate *next step* in diagnosis given the strong clinical suspicion. *High dose dexamethasone suppression test* - This test is specifically used to differentiate between **Cushing's disease** (pituitary ACTH excess) and other causes of Cushing's syndrome. - The patient's symptoms are not consistent with excessive cortisol production, making this test inappropriate for his chief complaint.

Question 146: A 16-year-old woman is brought to the emergency department by her family for not being responsive. The patient had locked herself in her room for several hours after breaking up with her boyfriend. When her family found her, they were unable to arouse her and immediately took her to the hospital. The patient has a past medical history of anorexia nervosa, which is being treated, chronic pain, and depression. She is not currently taking any medications. The patient has a family history of depression in her mother and grandmother. IV fluids are started, and the patient seems to be less somnolent. Her temperature is 101°F (38.3°C), pulse is 112/min, blood pressure is 90/60 mmHg, respirations are 18/min, and oxygen saturation is 95% on room air. On physical exam, the patient is somnolent and has dilated pupils and demonstrates clonus. She has dry skin and an ultrasound of her bladder reveals 650 mL of urine. The patient is appropriately treated with sodium bicarbonate. Which of the following is the best indicator of the extent of this patient's toxicity?

A. QRS prolongation (Correct Answer)
B. QT prolongation
C. Serum drug level
D. Anion gap acidosis
E. Liver enzyme elevation

Explanation: ***QRS prolongation*** - This patient's symptoms (including **hyperthermia**, **tachycardia**, **hypotension**, **dilated pupils**, **somnolence**, and **clonus**) along with her history of depression suggest **tricyclic antidepressant (TCA) toxicity**. - **QRS prolongation** on an EKG (greater than 100 ms) is the most reliable indicator of severe TCA toxicity and predicts the risk of **seizures** and **ventricular arrhythmias**. *QT prolongation* - While some drugs cause QT prolongation, **TCA toxicity** primarily causes sodium channel blockade leading to **QRS widening**, which is a more critical indicator of immediate cardiotoxicity risk. - QT prolongation is seen in toxicities involving potassium channel blockade, which is not the primary mechanism of severe TCA cardiotoxicity. *Serum drug level* - **Serum drug levels** of TCAs do not reliably correlate with the severity of toxicity due to variable metabolism, protein binding, and individual patient sensitivity. - Clinical signs and EKG findings are more important in guiding management. *Anion gap acidosis* - Although **metabolic acidosis** can occur in severe overdose, it is not specific to TCA toxicity and is a less direct indicator of the immediate cardiotoxic and neurotoxic risk compared to QRS prolongation. - Anion gap can be elevated due to various reasons in a critically ill patient. *Liver enzyme elevation* - **Liver enzyme elevation** is not an immediate or primary indicator of acute TCA overdose severity. - Liver toxicity can occur with chronic use or some specific drug overdoses, but it is not the most pertinent marker for acute, life-threatening TCA toxicity.

Question 147: A 32-year-old man with a history of alcohol binge drinking and polysubstance use is found down in his hotel room with bottles of alcohol, oxycodone, alprazolam, amphetamine-dextroamphetamine, and tadalafil. When EMS arrives, he appears comatose with pinpoint pupils and oxygen saturation of 80% on room air. He is intubated at the scene and airlifted to the nearest intensive care unit. Body temperature is 95 degrees F (35 degrees C). Creatine phosphokinase is 12,000 U/L. MRI of the brain demonstrates extensive infarcts consistent with acute hypoxic ischemic injury. Which of the following is the likely culprit for his overdose?

A. Amphetamines
B. Phosphodiesterase-5 (PDE-5) inhibitors
C. Alcohol
D. Benzodiazepines
E. Opioids (Correct Answer)

Explanation: ***Opioids*** - The patient's presentation with **pinpoint pupils**, **respiratory depression** (oxygen saturation 80%, requiring intubation), and coma is highly characteristic of **opioid overdose**. - **Hypothermia** and **rhabdomyolysis** (elevated CK) are common complications of severe opioid toxicity due to prolonged immobility and hypoperfusion. *Amphetamines* - Amphetamine overdose typically causes **mydriasis (dilated pupils)**, **tachycardia**, **hypertension**, and **hyperthermia**, which are contrary to the patient's presentation. - While amphetamines can cause rhabdomyolysis and altered mental status, the pinpoint pupils and hypothermia rule it out as the primary cause of his comatose state. *Phosphodiesterase-5 (PDE-5) inhibitors* - PDE-5 inhibitors like tadalafil primarily cause **vasodilation**, which can lead to **hypotension**, headaches, and flushing. - They do not typically cause **respiratory depression**, **pinpoint pupils**, or coma, making it an unlikely culprit for this severe presentation. *Alcohol* - While excessive alcohol consumption can cause **CNS depression**, coma, and respiratory depression, it typically results in **dilated or normal pupils**, not pinpoint pupils. - The combination of pinpoint pupils and severe respiratory depression points more strongly towards opioid toxicity. *Benzodiazepines* - Benzodiazepine overdose causes **CNS depression**, respiratory depression, and coma, but typically presents with **normal or slightly dilated pupils**. - While benzodiazepines can exacerbate opioid effects, the classic **pinpoint pupils** are the key differentiating factor pointing to opioids.

Question 148: A 21-year-old man presents with eye redness, itching, and watering; nasal congestion, and rhinorrhea. He reports that these symptoms have been occurring every year in the late spring since he was 18 years old. The patient’s medical history is significant for endoscopic resection of a right maxillary sinus polyp at the age of 16. His father and younger sister have bronchial asthma. He takes oxymetazoline as needed to decrease nasal congestion. The patient’s blood pressure is 120/80 mm Hg, heart rate is 71/min, respiratory rate is 18/min, and temperature is 36.7°C (98.0°F). On physical examination, there is conjunctival injection and clear nasal discharge bilaterally. His lymph nodes are not enlarged and his sinuses do not cause pain upon palpation. Heart and lung sounds are normal. Which of the following is most likely to be a part of his condition’s pathogenesis?

A. Secretion of granzymes and perforin by cytotoxic T lymphocytes
B. Excessive release of histamine by the mast cells (Correct Answer)
C. Production of specific IgM antibodies by B lymphocytes
D. Release of reactive oxygen species by neutrophils
E. IL-2 secretion by Th1 lymphocytes

Explanation: ***Excessive release of histamine by the mast cells*** - This patient presents with symptoms highly suggestive of **allergic rhinitis** and **allergic conjunctivitis**, including seasonal conjunctival injection, itching, watering, nasal congestion, and rhinorrhea, which started in late spring. This is a classic presentation of a **Type I hypersensitivity reaction**, mediated by IgE antibodies primarily acting on **mast cells**. - Upon re-exposure to the allergen (e.g., pollen in late spring), IgE antibodies cross-link on the surface of **mast cells**, leading to their **degranulation** and the release of preformed mediators, most notably **histamine**. Histamine causes the increased vascular permeability, vasodilation, itching, and mucous secretion characteristic of these allergic conditions. *Secretion of granzymes and perforin by cytotoxic T lymphocytes* - The secretion of granzymes and perforin by **cytotoxic T lymphocytes (CTLs)** is characteristic of **Type IV hypersensitivity reactions** (cell-mediated immunity) or direct viral killing, where CTLs target and destroy infected or abnormal cells. - This mechanism is not directly involved in the acute allergic symptoms described, which are humorally mediated by IgE and mast cells. *Production of specific IgM antibodies by B lymphocytes* - While B lymphocytes produce antibodies, the primary antibody class involved in **Type I hypersensitivity** (allergic reactions) is **IgE**, not IgM. - IgM antibodies are typically involved in the primary immune response and activate the complement system, which is characteristic of **Type II** and **Type III hypersensitivity reactions**, not allergic rhinitis. *Release of reactive oxygen species by neutrophils* - The release of **reactive oxygen species (ROS)** by **neutrophils** is a key mechanism of innate immunity, primarily involved in combating bacterial and fungal infections through phagocytosis and oxidative burst. - This process is associated with inflammation and tissue damage in various conditions but is not the primary pathway for the acute allergic symptoms seen in this patient. *IL-2 secretion by Th1 lymphocytes* - **IL-2** secretion by **Th1 lymphocytes** is crucial for the proliferation and differentiation of T cells and is central to cell-mediated immune responses, including **Type IV hypersensitivity reactions**. - **Allergic reactions (Type I hypersensitivity)** are predominantly driven by **Th2 lymphocytes** which secrete cytokines like IL-4, IL-5, and IL-13, promoting IgE production and eosinophil activation, not Th1-mediated responses.

Question 149: A 67-year-old man with type 2 diabetes mellitus and benign prostatic hyperplasia comes to the physician because of a 2-day history of sneezing and clear nasal discharge. He has had similar symptoms occasionally in the past. His current medications include metformin and tamsulosin. Examination of the nasal cavity shows red, swollen turbinates. Which of the following is the most appropriate pharmacotherapy for this patient's condition?

A. Nizatidine
B. Diphenhydramine
C. Amoxicillin
D. Theophylline
E. Desloratadine (Correct Answer)

Explanation: **Desloratadine** * This patient presents with symptoms consistent with **allergic rhinitis** (sneezing, clear nasal discharge, red/swollen turbinates, recurrent episodes). Desloratadine is a **second-generation antihistamine** that effectively treats these symptoms with minimal sedative effects, making it suitable for an elderly patient. * It is a **non-sedating** antihistamine, which is crucial for elderly patients due to their increased sensitivity to sedative effects and potential for falls or cognitive impairment with first-generation antihistamines. *Nizatidine* * **Nizatidine** is an **H2-receptor antagonist** primarily used to treat gastroesophageal reflux disease (GERD) and peptic ulcers, not allergic rhinitis. * It specifically blocks histamine H2 receptors in the stomach to reduce acid secretion and would not alleviate nasal congestion or sneezing. *Diphenhydramine* * **Diphenhydramine** is a **first-generation antihistamine** that is commonly used for allergic symptoms. However, it causes significant **sedation and anticholinergic side effects** (e.g., urinary retention, dry mouth, blurred vision). * Given the patient's age and **benign prostatic hyperplasia (BPH)**, diphenhydramine is contraindicated. Its **anticholinergic effects** can inhibit bladder detrusor muscle contraction, leading to **urinary retention**, which is particularly problematic in elderly men with BPH who already have obstructive urinary symptoms. *Amoxicillin* * **Amoxicillin** is an **antibiotic** used to treat bacterial infections. This patient's symptoms (clear nasal discharge, sneezing, similar past episodes) are characteristic of **allergic or viral rhinitis**, not a bacterial infection. * Using antibiotics for non-bacterial conditions contributes to **antibiotic resistance** and provides no therapeutic benefit for allergic symptoms. *Theophylline* * **Theophylline** is a **bronchodilator** primarily used for chronic respiratory conditions like asthma and COPD. It is not indicated for the treatment of allergic rhinitis. * It has a **narrow therapeutic index** and can cause significant side effects (e.g., nausea, arrhythmias, seizures), making it an inappropriate and potentially dangerous choice for allergic rhinitis.

Question 150: A 28-year-old gravida-2-para-1 at 12 weeks gestation presents for a prenatal visit. Over the past week, she has felt increasingly tired, even after waking up in the morning. She is vegan and avoids all animal products. She was diagnosed with Graves’ disease 6 months ago. Before conception, methimazole was switched to propylthiouracil (PTU). Other medications include folic acid and a multivitamin. The vital signs include: temperature 37.1℃ (98.8℉), pulse 72/min, respiratory rate 12/min, and blood pressure 110/75 mm Hg. The conjunctivae and nail beds are pale. Petechiae are present over the distal lower extremities. The pelvic examination reveals a uterus consistent in size with a 12-week gestation. Examination of the neck, lungs, heart, and abdomen shows no abnormalities. The laboratory studies show the following: Laboratory test Hemoglobin 9.0 g/dL Mean corpuscular volume 90 μm3 Leukocyte count 4,000/mm3 Segmented neutrophils 55% Lymphocytes 40% Platelet count 110,000/mm3 Serum Thyroid-stimulating hormone 0.1 μU/mL Thyroxine (T-4) 8 μg/dL Lactate dehydrogenase 60 U/L Total bilirubin 0.5 mg/dL Iron 100 μg/dL Ferritin 110 ng/mL Total iron-binding capacity 250 μg/dL Which of the following best explains these findings?

A. Excess antithyroid medication
B. Drug-induced marrow failure (Correct Answer)
C. Vitamin B12 deficiency
D. Hemodilution of pregnancy
E. Autoimmune hemolysis

Explanation: **Drug-induced marrow failure** - The patient's **pancytopenia** (low hemoglobin, leukocytes, and platelets) along with petechiae, in the context of **propylthiouracil (PTU)** use, strongly suggests drug-induced bone marrow suppression. PTU is known to cause agranulocytosis and, less commonly, aplastic anemia. - The **normal thyroid hormone levels** (TSH 0.1 μU/mL, T4 8 μg/dL) indicate that her Graves' disease is adequately controlled, but the hematological changes are severe enough to point towards a drug-related adverse effect rather than thyroid dysfunction. *Excess antithyroid medication* - While excess antithyroid medication like PTU can lead to **hypothyroidism**, the patient's low TSH (though near normal during pregnancy due to hCG effects) and normal T4 indicate she is **not hypothyroid**. - Hypothyroidism does not directly cause **pancytopenia** or petechiae, which are observed in this case. *Vitamin B12 deficiency* - **Vitamin B12 deficiency** typically causes **macrocytic anemia** (high MCV), and sometimes pancytopenia. However, this patient has a **normal MCV (90 μm3)**. - Although the patient is vegan, she is taking a multivitamin and folic acid, and iron studies are normal, making B12 deficiency less likely given the MCV. *Hemodilution of pregnancy* - **Physiologic hemodilution** in pregnancy can cause a *mild drop* in hemoglobin and hematocrit and a *slight decrease* in platelet count but typically does not lead to **leukopenia** or significant thrombocytopenia with petechiae. - The degree of *pancytopenia* observed here is beyond what would be expected from normal hemodilution. *Autoimmune hemolysis* - **Autoimmune hemolysis** would primarily cause **anemia** and potentially elevated bilirubin and LDH due to red blood cell destruction, but it does **not explain the leukopenia or thrombocytopenia** (pancytopenia). - The patient's bilirubin and LDH are normal, making significant hemolysis unlikely.

Question 151: A 25-year-old man is brought to the emergency department by police for abnormal behavior in a mini-market. The patient was found passed out in the aisle, and police were unable to arouse him. The patient has a past medical history of alcohol abuse and is not currently taking any medications according to his medical records. His temperature is 99.5°F (37.5°C), blood pressure is 120/87 mmHg, pulse is 50/min, respirations are 5/min, and oxygen saturation is 93% on room air. On physical exam, the patient is minimally responsive. He responds to painful stimuli by retracting his limbs and groaning, but otherwise does not answer questions or obey commands. Which of the following is most likely to be found in this patient?

A. Visual hallucinations
B. Conjunctival hyperemia
C. Hyperactive bowel sounds
D. Mydriasis
E. Miosis (Correct Answer)

Explanation: ***Miosis*** - The patient's presentation with **respiratory depression**, **bradycardia**, **miosis** (pinpoint pupils), and **depressed mental status** is highly suggestive of **opioid overdose**. - **Miosis** is a classic and nearly pathognomonic sign of opioid toxicity due to opioid-induced parasympathetic stimulation. *Visual hallucinations* - **Visual hallucinations** are more commonly associated with conditions like **alcohol withdrawal** (delirium tremens), stimulant intoxication, or certain psychiatric disorders. - They are not a typical feature of acute opioid overdose, which primarily causes central nervous system depression. *Conjunctival hyperemia* - **Conjunctival hyperemia** (red eyes) is frequently observed with **cannabis intoxication** or certain inhalant exposures. - This sign is not characteristic of an opioid overdose; rather, pupils are typically constricted. *Hyperactive bowel sounds* - **Hyperactive bowel sounds** can be seen in conditions causing increased gastrointestinal motility, such as **gastroenteritis** or early stages of bowel obstruction. - Opioids typically cause **decreased gastrointestinal motility**, leading to **constipation** and often diminished or absent bowel sounds, not hyperactive ones. *Mydriasis* - **Mydriasis** (dilated pupils) is typically associated with sympathomimetic toxicity (e.g., **cocaine**, **amphetamine**), anticholinergic poisoning (e.g., **atropine**), or severe anoxia. - In direct contrast, opioids cause **miosis**.

Question 152: A researcher is studying receptors that respond to epinephrine in the body and discovers a particular subset that is expressed in presynaptic adrenergic nerve terminals. She discovers that upon activation, these receptors will lead to decreased sympathetic nervous system activity. She then studies the intracellular second messenger changes that occur when this receptor is activated. She records these changes and begins searching for analogous receptor pathways. Which of the following receptors would cause the most similar set of intracellular second messenger changes?

A. Muscarinic cholinoreceptors in the gastrointestinal tract
B. Growth hormone receptors in the musculoskeletal system
C. Vasopressin receptors in the kidney
D. Dopamine receptors in the brain (Correct Answer)
E. Aldosterone receptors in the kidney

Explanation: ***Dopamine receptors in the brain*** - The described presynaptic receptors for epinephrine that decrease sympathetic activity are **alpha-2 adrenergic receptors**, which are **G inhibitory protein (Gi)-coupled receptors**. - Gi-coupled receptors **inhibit adenylyl cyclase**, leading to a **decrease in intracellular cAMP**, a signaling pathway shared by **D2 dopamine receptors**. *Muscarinic cholinoreceptors in the gastrointestinal tract* - Most muscarinic receptors (M1 and M3) in the GI tract are **Gq-coupled**, leading to an **increase in phospholipase C (PLC) activity**, ultimately increasing intracellular **IP3 and DAG** and promoting smooth muscle contraction. - This mechanism is distinct from the **Gi-mediated inhibition of cAMP** described for the presynaptic adrenergic receptor. *Growth hormone receptors in the musculoskeletal system* - Growth hormone receptors are **tyrosine kinase-associated receptors** (specifically, they are linked to **JAK/STAT pathways**), not G protein-coupled receptors. - Their intracellular signaling involves **protein phosphorylation cascades**, which are fundamentally different from second messenger changes involving cAMP. *Vasopressin receptors in the kidney* - Vasopressin (ADH) acts on **V2 receptors** in the kidney, which are **G stimulatory protein (Gs)-coupled receptors**. - Activation of V2 receptors leads to an **increase in adenylyl cyclase activity** and thus an **increase in intracellular cAMP**, the opposite effect of the described Gi-coupled receptor. *Aldosterone receptors in the kidney* - Aldosterone receptors are **intracellular steroid hormone receptors** that directly bind to DNA and regulate gene transcription. - They do not engage in rapid intracellular second messenger changes like G protein-coupled receptors, but rather alter **protein synthesis** over hours to days.

Question 153: A 33-year-old man comes to the emergency department because of a dry mouth and blurred vision for the past 30 minutes. Prior to this, he was on a road trip and started to feel nauseous, dizzy, and fatigued, so his friend gave him a drug that had helped in the past. Physical examination shows dry mucous membranes and dilated pupils. The remainder of the examination shows no abnormalities. Administration of which of the following drugs is most likely to cause a similar adverse reaction in this patient?

A. Loratadine
B. Phenylephrine
C. Oxycodone
D. Oxybutynin (Correct Answer)
E. Pilocarpine

Explanation: ***Oxybutynin*** - Oxybutynin is an **anticholinergic** drug primarily used to treat overactive bladder. - Its adverse effects, such as **dry mouth** (xerostomia), blurred vision (due to cycloplegia and mydriasis), nausea, dizziness, and fatigue, are directly related to its **muscarinic receptor blockade**. *Loratadine* - Loratadine is a **second-generation antihistamine** that is largely non-sedating and has minimal anticholinergic effects. - While it can cause dry mouth in rare cases, it is much less likely to cause the constellation of severe anticholinergic symptoms seen here, especially **blurred vision due to mydriasis**. *Phenylephrine* - Phenylephrine is an **alpha-1 adrenergic agonist** used as a decongestant or to increase blood pressure. - Its primary effects are vasoconstriction; it does not typically cause dry mouth, blurred vision, or the other anticholinergic symptoms described. *Oxycodone* - Oxycodone is an **opioid analgesic** that primarily acts on mu-opioid receptors. - Common side effects include constipation, nausea, sedation, and respiratory depression, but not dry mouth or blurred vision as a prominent anticholinergic effect. *Pilocarpine* - Pilocarpine is a **muscarinic agonist** used to treat dry mouth or glaucoma. - It would cause symptoms directly opposite to those observed, such as increased salivation and miosis, rather than dry mouth and dilated pupils.

Question 154: A 50-year-old woman presents with acute onset fever and chills for the past hour. She mentions earlier in the day she felt blue, so she took some St. John’s wort because she was told by a friend that it helps with depression. Past medical history is significant for hypertension, diabetes mellitus, and depression managed medically with captopril, metformin, and fluoxetine. She has no history of allergies. Her pulse is 130/min, the respiratory rate is 18/min, the blood pressure is 176/92 mm Hg, and the temperature is 38.5°C (101.3°F). On physical examination, the patient is profusely diaphoretic and extremely irritable when asked questions. Oriented x 3. The abdomen is soft and nontender with no hepatosplenomegaly. Increased bowel sounds are heard in the abdomen. Deep tendon reflexes are 3+ bilaterally and clonus is elicited. The sensation is decreased in the feet bilaterally. Mydriasis is present. Fingerstick glucose is 140 mg/dL. An ECG shows sinus tachycardia but is otherwise normal. Which of the following is the most likely cause of this patient’s condition?

A. Sepsis
B. Anaphylactic reaction
C. Diabetic ketoacidosis
D. Neuroleptic malignant syndrome
E. Serotonin syndrome (Correct Answer)

Explanation: ***Serotonin syndrome*** - The patient's presentation with **fever, diaphoresis, hypertension, tachycardia, hyperreflexia, clonus, mydriasis**, and **agitation** after combining an **SSRI (fluoxetine)** with **St. John's wort** (a serotonin-enhancing herbal supplement) is highly characteristic of serotonin syndrome. - This condition results from excessive serotonergic activity in the central and peripheral nervous system. *Sepsis* - While **fever, chills, and tachycardia** can be indicators of sepsis, the presence of specific neurological and neuromuscular signs like **hyperreflexia, clonus, and mydriasis** points away from it. - The patient's **irritable state and normal mental orientation** is less typical for severe sepsis, which often involves altered mental status. *Anaphylactic reaction* - **Anaphylaxis** presents with rapid onset of symptoms such as **urticaria, angioedema, bronchospasm, and hypotension**, which are not observed in this patient. - There is no history of allergen exposure, and the prominent neurological symptoms are not typical of anaphylaxis. *Diabetic ketoacidosis* - **DKA** is characterized by **hyperglycemia, metabolic acidosis, and ketonemia**, often presenting with Kussmaul respirations and fruity breath odor. - The patient's **fingerstick glucose (140 mg/dL)** is not significantly elevated, and there is no mention of deep, rapid breathing or other DKA-specific symptoms. *Neuroleptic malignant syndrome* - **NMS** is typically associated with exposure to **dopamine antagonists (antipsychotics)** and is characterized by **severe muscle rigidity, hyperthermia, altered mental status, and autonomic instability.** - While some symptoms overlap, this patient's history of St. John's wort and fluoxetine points to increased serotonin, and the specific neuromuscular findings like clonus are more indicative of serotonin syndrome.

Question 155: A 32-year-old woman presents with diplopia. She says that she has been experiencing drooping of her eyelids and severe muscle weakness. She reports that her symptoms are worse at the end of the day. Which of the following additional findings would most likely be seen in this patient?

A. Increased acetylcholine receptor antibody (Correct Answer)
B. Albuminocytological dissociation in the cerebrospinal fluid
C. Increased calcium channel receptor antibodies
D. Increased serum creatine kinase levels
E. Increased antinuclear antibodies

Explanation: ***Increased acetylcholine receptor antibody*** - The patient's symptoms of **diplopia**, **ptosis** (drooping eyelids), and severe muscle weakness that worsens with activity (end of the day) are classic manifestations of **myasthenia gravis**. - **Myasthenia gravis** is an autoimmune disorder characterized by the destruction of **acetylcholine receptors** at the neuromuscular junction, which is confirmed by the presence of **acetylcholine receptor antibodies**. *Albuminocytological dissociation in the cerebrospinal fluid* - This finding, characterized by **elevated CSF protein** with a normal white blood cell count, is a hallmark of **Guillain-Barré syndrome**. - **Guillain-Barré syndrome** typically presents with ascending paralysis and areflexia, which is distinct from the fluctuating, fatigable weakness seen in this patient. *Increased calcium channel receptor antibodies* - The presence of **voltage-gated calcium channel (VGCC) antibodies** is characteristic of **Lambert-Eaton Myasthenic Syndrome (LEMS)**. - While LEMS also causes muscle weakness, it often improves with activity and is frequently associated with **small cell lung cancer**, differentiating it from myasthenia gravis where weakness worsens with activity. *Increased serum creatine kinase levels* - Elevated **creatine kinase (CK)** levels are indicative of **muscle damage or inflammation**, as seen in conditions like **myositis** or **muscular dystrophies**. - Myasthenia gravis is a disorder of neuromuscular transmission, not primary muscle damage, so CK levels are typically normal. *Increased antinuclear antibodies* - **Antinuclear antibodies (ANA)** are a common finding in **systemic autoimmune diseases** like **systemic lupus erythematosus (SLE)** or **Sjögren's syndrome**. - While some autoimmune conditions can have overlapping features, the specific symptom complex presented (diplopia, ptosis, fatigable weakness) strongly points to myasthenia gravis rather than a systemic autoimmune connective tissue disease.

Question 156: A 42-year-old man is admitted to the hospital for pain and swelling in his right foot. His temperature is 39.7°C (103.5°F), pulse is 116/min, respirations are 23/min, and blood pressure is 69/39 mmHg. A drug is administered via a peripheral intravenous line that works primarily by increasing inositol trisphosphate concentrations in arteriolar smooth muscle cells. Eight hours later, the patient has pain at the right antecubital fossa. Examination shows the skin around the intravenous line site to be pale and cool to touch. After discontinuing the infusion, which of the following is the most appropriate pharmacotherapy to prevent further tissue injury in this patient?

A. Conivaptan
B. Tamsulosin
C. Heparin
D. Phentolamine (Correct Answer)
E. Procaine

Explanation: ***Phentolamine*** - The patient received a drug that increases **inositol trisphosphate** (IP3) concentrations in arteriolar smooth muscle cells, leading to **vasoconstriction**. This is characteristic of an **alpha-1 adrenergic agonist**, such as **norepinephrine** or **phenylephrine**, often used in septic shock to increase blood pressure. - The symptoms of **pain, pallor, and coolness** at the IV site suggest **extravasation** with localized vasoconstriction and tissue ischemia. **Phentolamine** is an **alpha-adrenergic antagonist** that can reverse this vasoconstriction, reducing tissue damage. *Conivaptan* - **Conivaptan** is a **vasopressin (ADH) receptor antagonist**, primarily used to treat **hyponatremia** and sometimes heart failure. - It works by blocking V1a and V2 receptors, leading to increased free water excretion and vasodilation, which is not the primary issue or desired reversal in this case of extravasation. *Tamsulosin* - **Tamsulosin** is a **selective alpha-1a adrenergic antagonist** primarily used to treat **benign prostatic hyperplasia (BPH)** by relaxing smooth muscle in the prostate and bladder neck. - Its selectivity for alpha-1a receptors means it would be less effective in reversing the generalized vasoconstriction caused by extravasated alpha-adrenergic agonists compared to a non-selective alpha-antagonist like phentolamine. *Heparin* - **Heparin** is an **anticoagulant** that prevents clot formation and is used in conditions like deep vein thrombosis or pulmonary embolism. - The patient's symptoms are due to **vasoconstriction and tissue ischemia**, not thrombosis, so an anticoagulant would not directly address the underlying mechanism of injury. *Procaine* - **Procaine** is a **local anesthetic** that blocks nerve impulse transmission, causing numbness. - While it could temporarily relieve pain, it does not address the underlying **vasoconstriction and tissue ischemia** that is causing the tissue injury, and therefore would not prevent further damage.

Question 157: A 22-year-old woman comes to the physician because of a 12-week history of persistent cough. The cough is nonproductive and worse at night. She otherwise feels well. She has not had any changes in appetite or exercise tolerance. For the past year, she has smoked an occasional cigarette at social occasions. Use of herbal cough medications has not provided any symptom relief. She has no history of serious illness but reports getting a runny nose every morning during winter. Her temperature is 37°C (98.6°F), pulse is 68/min, respirations are 12/min, and blood pressure is 110/76 mm Hg. Cardiopulmonary examination and an x-ray of the chest show no abnormalities. Her FEV1 is normal. Which of the following is the most appropriate next step in management?

A. Oral amoxicillin-clavulanate
B. Oral acetylcysteine
C. Prednisone therapy
D. Oral diphenhydramine (Correct Answer)
E. Codeine syrup

Explanation: ***Oral diphenhydramine*** - The patient's symptoms, including a chronic, nonproductive cough that is worse at night and a history of seasonal **rhinitis** (**"runny nose every morning during winter"**), are highly suggestive of **upper airway cough syndrome (UACS)**, also known as post-nasal drip. - **First-generation antihistamines** like diphenhydramine, often combined with a decongestant, are the initial treatment of choice for UACS due to their anticholinergic and antihistaminic effects that help dry up secretions and reduce inflammation. *Oral amoxicillin-clavulanate* - This is an **antibiotic** indicated for bacterial infections. The patient's normal vital signs, clear chest x-ray, nonproductive cough, and absence of fever or purulent sputum make a bacterial infection highly unlikely. - Using antibiotics unnecessarily contributes to **antibiotic resistance** and does not address non-bacterial causes of cough. *Oral acetylcysteine* - **Acetylcysteine** is a mucolytic agent used to thin respiratory secretions in conditions like cystic fibrosis or chronic bronchitis. - The patient's cough is described as **nonproductive**, indicating a lack of significant mucus, making acetylcysteine an inappropriate treatment. *Prednisone therapy* - **Prednisone** is a corticosteroid used for inflammatory conditions like asthma or severe allergic reactions. - While asthma can cause chronic cough, the patient's normal FEV1 and absence of wheezing or dyspnea make asthma less likely, and starting oral corticosteroids empirically without a clear diagnosis is generally not recommended. *Codeine syrup* - **Codeine** is an opioid cough suppressant, typically reserved for severe, debilitating coughs when other treatments have failed and the underlying cause is addressed. - It has potential side effects including sedation and constipation, and its use is not appropriate as a first-line treatment for what appears to be UACS, which has a specific and effective non-opioid treatment.

Question 158: A 24-year-old man who is postoperative day 1 after an emergency appendectomy is evaluated by the team managing his care. He complains that he still has not been able to urinate after removal of the urinary catheter that was inserted during surgery. Given this issue, he is started on a medication that acts on a post-synaptic receptor and is resistant to a synaptic esterase. Which of the following is most likely another use of the medication that was administered in this case?

A. Glaucoma management
B. Bronchial airway challenge test
C. Pupillary contraction
D. Neurogenic ileus (Correct Answer)
E. Diagnosis of myasthenia gravis

Explanation: ***Neurogenic ileus*** - The medication described is **bethanechol**, a direct-acting muscarinic agonist that acts on post-synaptic M3 receptors and is **resistant to acetylcholinesterase** (unlike acetylcholine) - Bethanechol is used for **post-operative urinary retention** by stimulating detrusor muscle contraction and relaxing the trigone and sphincter - Another major clinical use is treating **neurogenic ileus** and post-operative ileus by stimulating GI smooth muscle motility and increasing peristalsis - It directly activates muscarinic receptors on bladder and GI smooth muscle *Diagnosis of myasthenia gravis* - This is **incorrect** - bethanechol is NOT used for myasthenia gravis diagnosis - **Edrophonium** (Tensilon test) or **neostigmine** are used for MG diagnosis - these are acetylcholinesterase inhibitors, not direct muscarinic agonists - Bethanechol's mechanism (direct muscarinic agonist) would not effectively test for nicotinic receptor antibodies at the neuromuscular junction *Glaucoma management* - While some muscarinic agonists are used in glaucoma (e.g., **pilocarpine**), bethanechol is not typically used for this indication - Pilocarpine reduces intraocular pressure by contracting the ciliary muscle and increasing aqueous humor outflow - Bethanechol's systemic effects and lack of ocular specificity make it unsuitable for glaucoma management *Bronchial airway challenge test* - **Methacholine**, not bethanechol, is the muscarinic agonist used for bronchial provocation testing in asthma diagnosis - While bethanechol can cause bronchoconstriction, it is not standardized or used for airway challenge tests - Methacholine has better-characterized dose-response relationships for pulmonary function testing *Pupillary contraction* - While muscarinic agonists cause miosis (pupillary contraction), this is a **side effect** rather than a therapeutic indication for bethanechol - Direct application of muscarinic agonists to the eye (like pilocarpine) would be used if miosis were the goal - Bethanechol is given systemically for bladder and GI indications, not for ophthalmologic purposes

Question 159: A 67-year-old man presents to the emergency department acutely confused. The patient's wife found him mumbling incoherently in the kitchen this morning as they were preparing for a hike. The patient was previously healthy and only had a history of mild forgetfulness, depression, asthma, and seasonal allergies. His temperature is 98.5°F (36.9°C), blood pressure is 122/62 mmHg, pulse is 119/min, and oxygen saturation is 98% on room air. The patient is answering questions inappropriately and seems confused. Physical exam is notable for warm, flushed, and dry skin. The patient's pupils are dilated. Which of the following is also likely to be found in this patient?

A. Hypoventilation
B. QRS widening
C. Coronary artery vasospasm
D. Increased bronchial secretions
E. Urinary retention (Correct Answer)

Explanation: ***Urinary retention*** - The patient's symptoms (dilated pupils, warm/flushed/dry skin, confusion, tachycardia) are consistent with **anticholinergic toxidrome**. - **Urinary retention** is a common manifestation of anticholinergic toxicity due to the paralysis of the detrusor muscle and contraction of the urethral sphincter. *Hypoventilation* - Anticholinergic toxicity typically causes **tachycardia** and may lead to tachypnea, not hypoventilation. - Respiratory depression is more characteristic of **opioid** or **sedative-hypnotic** overdose. *QRS widening* - **QRS widening** is characteristic of **sodium channel blockade**, as seen with tricyclic antidepressant overdose, which can have anticholinergic effects but primarily causes cardiac toxicity via sodium channel blockade. - While anticholinergics can cause arrhythmias, QRS widening specific to this mechanism isn't a primary feature of pure anticholinergic toxidrome. *Coronary artery vasospasm* - **Coronary artery vasospasm** is not a direct effect of anticholinergic toxicity. - It is more commonly associated with drug use such as **cocaine**, or certain medications like **5-fluorouracil**. *Increased bronchial secretions* - Anticholinergic agents **decrease bronchial secretions** by blocking muscarinic receptors in the airway smooth muscle and glands. - Increased bronchial secretions are characteristic of **cholinergic overdose**.

Question 160: A 71-year-old male is admitted to the hospital with a Staphylococcal aureus infection of his decubitus ulcers. He is diabetic and has a body mass index of 45. His temperature is 37°C (98.6°F), respirations are 15/min, pulse is 67/min and blood pressure is 122/98 mm Hg. The nurse is monitoring his blood glucose and records it as 63 mg/dL. She then asks the resident on call if the patient should receive glargine insulin as ordered seeing his glucose levels. Which of the following would be the most appropriate response by the resident?

A. No, due to his S. aureus infection he is more likely to have low blood glucose and glargine insulin should be held until he has recovered.
B. No, glargine insulin was probably ordered in error as it is not recommended in type 2 diabetes.
C. No, glargine insulin should be stopped and replaced with lispro insulin until his blood glucose increases.
D. Yes, glargine insulin is a long-acting insulin and should still be given to control his blood glucose over the next 24 hours.
E. No, glargine insulin should not be given during an episode of hypoglycemia as it will further lower blood glucose. (Correct Answer)

Explanation: ***No, glargine insulin should not be given during an episode of hypoglycemia as it will further lower blood glucose.*** - The patient's blood glucose is **63 mg/dL**, which is **hypoglycemic** (typically defined as <70 mg/dL). Administering additional long-acting insulin like glargine would further decrease blood glucose and potentially cause serious harm. - **Glargine insulin** is a **long-acting basal insulin** designed to provide a steady release of insulin over 24 hours. While crucial for long-term glucose control, it should be held during acute hypoglycemic episodes to prevent severe glucose drops. *No, due to his S. aureus infection he is more likely to have low blood glucose and glargine insulin should be held until he has recovered.* - Infections, especially severe ones, cause **physiological stress** and typically lead to **increased blood glucose levels** due to elevated counter-regulatory hormones, not lower levels. - While insulin should be held during a hypoglycemic episode, the reasoning given here regarding infection causing low blood glucose is generally incorrect; infections usually cause hyperglycemia. *No, glargine insulin was probably ordered in error as it is not recommended in type 2 diabetes.* - **Glargine insulin** is a commonly used and **effective basal insulin** for managing type 2 diabetes, especially when oral agents or other shorter-acting insulins are insufficient. - Basal insulin, like glargine, is a cornerstone in the treatment of many patients with **type 2 diabetes** to maintain stable glucose levels overnight and between meals. *No, glargine insulin should be stopped and replaced with lispro insulin until his blood glucose increases.* - **Lispro insulin** is a **rapid-acting insulin** used to cover meals or correct acute hyperglycemia; it is not a direct replacement for basal insulin like glargine, particularly in a hypoglycemic state. - **Stopping glargine** during hypoglycemia is correct, but replacing it with another insulin, especially rapid-acting, without addressing the hypoglycemia and understanding the cause would be inappropriate and potentially dangerous. *Yes, glargine insulin is a long-acting insulin and should still be given to control his blood glucose over the next 24 hours.* - While glargine is a long-acting insulin, administering it during an active state of **hypoglycemia (63 mg/dL)** is not appropriate, as it would worsen the low blood sugar. - The immediate priority in hypoglycemia is to **safely raise blood glucose**, not to administer more insulin, regardless of its duration of action.

Question 161: A 53-year-old woman presented to her PCP with one week of difficulty falling asleep, despite having good sleep hygiene. She denies changes in her mood, weight loss, and anhedonia. She has had difficulty concentrating and feels tired throughout the day. Recently, she was fired from her previous job. What medication would be most helpful for this patient?

A. Citalopram
B. Diphenhydramine
C. Quetiapine
D. Diazepam
E. Zolpidem (Correct Answer)

Explanation: ***Zolpidem*** - This patient presents with **insomnia** characterized by **difficulty falling asleep**, which is the primary indication for zolpidem. - Zolpidem is a **non-benzodiazepine GABA-A receptor agonist** that acts quickly to induce sleep, making it effective for sleep onset insomnia. *Citalopram* - **Citalopram** is an **SSRI** primarily used for treating depression and anxiety disorders, which are not explicitly indicated as primary issues for this patient. - While it can sometimes help with sleep in depressed patients, its **onset of action is slow** (weeks), and it is not a first-line agent for acute insomnia. *Diphenhydramine* - **Diphenhydramine** is an **antihistamine** with sedative properties, often used for occasional insomnia, but it can lead to significant **daytime sedation, anticholinergic side effects**, and is generally not recommended for chronic use. - The patient's presentation suggests a need for more targeted and potentially long-term management beyond an over-the-counter antihistamine. *Quetiapine* - **Quetiapine** is an **antipsychotic** medication that is sometimes used off-label for insomnia due to its sedative effects, but it carries significant **side effects** like metabolic syndrome, orthostatic hypotension, and tardive dyskinesia. - It is generally **not recommended as a first-line treatment for insomnia** without co-occurring psychiatric conditions like bipolar disorder or schizophrenia. *Diazepam* - **Diazepam** is a **benzodiazepine** that can be used for insomnia, but it has a **long half-life** leading to daytime sedation and a **high potential for dependence and abuse**. - Its use should be limited to short-term treatment of severe insomnia and is generally avoided in patients who deny mood changes and anhedonia, suggesting a less complex underlying issue.

Question 162: A 54-year-old man comes to the emergency department because of burning oral mucosal pain, chest pain, and shortness of breath that started one hour ago. He reports that the pain is worse when swallowing. Two years ago, he was diagnosed with major depressive disorder but does not adhere to his medication regimen. He lives alone and works as a farmer. He smokes 1 pack of cigarettes and drinks 6 oz of homemade vodka daily. The patient is oriented to person, place, and time. His pulse is 95/min, respirations are 18/min, and blood pressure is 130/85 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Examination of the oropharynx shows profuse salivation with mild erythema of the buccal mucosa, tongue, and epiglottis area. This patient has most likely sustained poisoning by which of the following substances?

A. Morphine
B. Amitriptyline
C. Parathion
D. Potassium hydroxide (Correct Answer)
E. Ethylene glycol

Explanation: ***Potassium hydroxide*** - The patient's symptoms of **burning oral mucosal pain**, worse with swallowing, along with **profuse salivation** and **erythema of the oropharynx**, are highly suggestive of a **caustic injury**. - **Potassium hydroxide** is a strong alkali that causes liquefactive necrosis, leading to deep penetrating injuries of the esophageal and gastric mucosa. *Morphine* - **Morphine** is an opioid that typically causes **central nervous system depression**, pinpoint pupils, and respiratory depression. - It does not cause localized burning pain or mucosal irritation as described. *Amitriptyline* - **Amitriptyline** is a tricyclic antidepressant; an overdose would likely present with anticholinergic effects like **tachycardia**, **mydriasis**, **dry mouth**, and potential cardiac arrhythmias. - It would not cause burning oral pain and erythema. *Parathion* - **Parathion** is an organophosphate insecticide that causes cholinergic crisis with symptoms such as **salivation**, lacrimation, urination, defecation, gastrointestinal upset, and emesis (**SLUDGE** syndrome). - While salivation is present, the absence of other prominent cholinergic signs (e.g., miosis, muscle fasciculations, bradycardia) and the highly localized burning pain make it less likely than a caustic injury. *Ethylene glycol* - **Ethylene glycol** poisoning typically presents with **metabolic acidosis**, renal failure, and CNS depression. - Immediate symptoms are often related to CNS effects (e.g., inebriation) and cardiopulmonary symptoms, not acute oral mucosal burning.

Question 163: A 43-year-old man is brought to the emergency department 45 minutes after his wife found him on the floor sweating profusely. On arrival, he is lethargic and unable to provide a history. He vomited multiple times on the way to the hospital. His temperature is 37.3°C (99.1°F), pulse is 55/min, respirations are 22/min, and blood pressure is 98/65 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 80%. Examination shows profuse diaphoresis and excessive salivation. He withdraws his extremities sluggishly to pain. The pupils are constricted and reactive. Scattered expiratory wheezing and rhonchi are heard throughout both lung fields. Cardiac examination shows no abnormalities. There are fine fasciculations in the lower extremities bilaterally. Muscle strength is reduced and deep tendon reflexes are 1+ bilaterally. His clothes are soaked with urine and feces. Which of the following is the mechanism of action of the most appropriate initial pharmacotherapy?

A. Non-selective α-adrenergic antagonism
B. Competitive antagonism of mACh receptors (Correct Answer)
C. Alkaloid emesis-induction
D. Enteral binding
E. Urine alkalization

Explanation: ***Competitive antagonism of mACh receptors*** - The patient's symptoms, including **profuse sweating, salivation, constricted pupils, wheezing, bradycardia, hypotension, fasciculations**, and incontinence, are classic signs of **cholinergic crisis** due to **organophosphate poisoning**. - **Atropine**, a competitive antagonist of muscarinic acetylcholine (mACh) receptors, is the primary initial pharmacotherapy for organophosphate poisoning, counteracting the excessive parasympathetic stimulation. *Non-selective α-adrenergic antagonism* - This mechanism would typically be used to treat conditions involving **excessive alpha-adrenergic activity**, such as a pheochromocytoma or severe hypertension. - It would **worsen the hypotension** already present in this patient and does not address the underlying cholinergic overstimulation. *Alkaloid emesis-induction* - While vomiting occurred, inducing further emesis with an alkaloid is **contraindicated** in cases of organophosphate poisoning due to the risk of **aspiration pneumonitis** and the patient's altered mental status. - Furthermore, modern management of poisoning rarely recommends routine emesis induction. *Enteral binding* - **Activated charcoal** acts by enteral binding to prevent absorption of toxins from the gastrointestinal tract. - While it may be considered in some poisonings, the rapid onset of severe symptoms and the potential for aspiration in a lethargic patient makes **airway protection** and **antidote administration** the immediate priorities. *Urine alkalization* - Urine alkalization is a technique used to enhance the renal excretion of certain acidic drugs by increasing their ionization in the urine, preventing reabsorption. - It is **not relevant** for the initial management of organophosphate poisoning, which primarily requires anticholinergic agents and cholinesterase reactivators.

Question 164: A 22-year-old man, accompanied by his brother, presents to the emergency department with palpitations for the past 30 minutes and nausea for the past hour. When the patient meets the physician, he says, “Doctor, I am the happiest person in the world because I have the best brain possible. It’s just that my heart is saying something, so I came to check with you to see what it is”. The brother says the patient was diagnosed with attention-deficit/hyperactivity disorder (ADHD) 5 years ago. When the doctor asks the patient about his ADHD treatment, he replies, “Doctor, the medicine is wonderful, and I love it very much. I often take one or two tablets extra!” He has no history of a known cardiovascular disorder, alcohol abuse, or smoking. The patient’s temperature is 99.2ºF (37.3ºC), heart rate is 116/minute, respiratory rate is 18/minute, and blood pressure is 138/94 mm Hg. Generalized perspiration is present. Which of the following signs is most likely to be present on ocular examination?

A. Bilateral optic disc edema
B. Conjunctival injection
C. Bilateral foveal yellow spots
D. Rotatory nystagmus
E. Dilated pupils (Correct Answer)

Explanation: ***Dilated pupils*** - This patient presents with symptoms such as **palpitations, nausea, hypertension, tachycardia, and generalized perspiration** following an overdose of his ADHD medication. This strongly suggests **sympathomimetic toxicity**, likely due to stimulant overdose. - **Stimulants** like those used for ADHD (e.g., methylphenidate, amphetamines) characteristically cause **mydriasis (dilated pupils)** due to their sympathomimetic effects on the autonomic nervous system. *Bilateral optic disc edema* - **Bilateral optic disc edema** is typically associated with **increased intracranial pressure**, not directly with sympathomimetic stimulant overdose. - While hypertension is present, it's usually **severe and prolonged hypertension** that can lead to hypertensive retinopathy and disc edema, which is not the primary ocular sign of acute stimulant toxicity. *Conjunctival injection* - **Conjunctival injection (red eyes)** is often seen in conditions like **allergic conjunctivitis, viral conjunctivitis, bacterial conjunctivitis, or glaucoma**, and is also a common sign of **cannabis use**. - It is **not a typical finding in sympathomimetic stimulant overdose**, which primarily affects adrenergic receptors leading to pupillary dilation. *Bilateral foveal yellow spots* - **Bilateral foveal yellow spots** can be a non-specific finding or associated with conditions like **macular degeneration**, certain **retinal dystrophies**, or **tamoxifen retinopathy**. - This finding is **not characteristic of acute stimulant toxicity** or its cardiovascular effects. *Rotatory nystagmus* - **Rotatory nystagmus** is an involuntary eye movement typically associated with **vestibular dysfunction, cerebellar lesions, or certain drug toxicities (e.g., phencyclidine, anticonvulsants)**. - While some drug intoxications can cause nystagmus, **stimulant overdose typically does not produce rotatory nystagmus** as a primary ocular sign, rather it affects pupillary size.

Question 165: A 46-year-old female with estrogen receptor positive invasive ductal carcinoma is prescribed tamoxifen. Which of the following is the MOST concerning side effect that requires patient counseling regarding potentially life-threatening complications?

A. Increased risk of deep vein thrombosis (Correct Answer)
B. Hot flashes and menopausal symptoms
C. Improved bone density in postmenopausal women
D. Increased risk of endometrial cancer
E. Increased risk of hypertension

Explanation: ***Increased risk of deep vein thrombosis*** - Tamoxifen, a **selective estrogen receptor modulator (SERM)**, has estrogen receptor agonist effects in some tissues, including the coagulation system. - This can lead to an increased risk of **thromboembolic events**, such as **deep vein thrombosis (DVT)** and **pulmonary embolism (PE)**, which are potentially life-threatening cardiovascular/hematologic complications. *Hot flashes and menopausal symptoms* - While tamoxifen commonly causes **hot flashes**, night sweats, and vaginal dryness due to its anti-estrogenic effects in the hypothalamus and vaginal tissue, these are generally a quality-of-life issue and not the **most concerning cardiovascular/hematologic side effect** requiring immediate intervention or counseling regarding life-threatening complications. - These symptoms are usually manageable and anticipated but do not pose the same acute danger as a thromboembolic event. *Improved bone density in postmenopausal women* - Tamoxifen has **estrogen-agonist effects on bone**, leading to improved bone mineral density in postmenopausal women. - This is generally considered a **beneficial side effect** rather than a concerning one, especially in women at risk for osteoporosis. *Increased risk of hypertension* - While cardiovascular side effects can occur with tamoxifen, a significantly increased risk of **hypertension** is not one of its primary or most concerning cardiovascular/hematologic complications. - Blood pressure needs to be monitored, but DVT/PE risk is a far greater concern. *Increased risk of endometrial cancer* - Tamoxifen has **estrogen-agonist effects on the endometrium**, increasing the risk of **endometrial hyperplasia** and **endometrial cancer**. - While this is a serious and well-known side effect that requires patient counseling and monitoring, it is an oncologic complication, not a cardiovascular or hematologic one.

Question 166: A 34-year-old male presents to clinic today complaining that his medication has stopped working. He states despite being able to manage the side effects, a voice has returned again telling him to hurt his Mother. You prescribe him a drug which has shown improved efficacy in treating his disorder but requires frequent followup visits. One week later he returns with the following lab results: WBC : 2500 cells/mcL, Neutrophils : 55% and, Bands : 1%. What drug was this patient prescribed?

A. Clozapine (Correct Answer)
B. Lurasidone
C. Olanzapine
D. Chlorpromazine
E. Haloperidol

Explanation: ***Clozapine*** - **Clozapine** is an atypical antipsychotic known for its superior efficacy in **treatment-resistant schizophrenia**, which fits the patient's presentation of a recurrence of symptoms despite prior medication. - The given lab results (WBC 2500 cells/mcL, Neutrophils 55%, Bands 1%) show signs of **neutropenia**, a severe side effect of clozapine that necessitates frequent monitoring of complete blood counts (CBCs). *Lurasidone* - **Lurasidone** is an atypical antipsychotic, but it is not typically considered a first-line treatment for treatment-resistant cases and does not carry the same risk of agranulocytosis requiring frequent CBC monitoring as clozapine. - It would not explain the **observed neutropenia** and the need for frequent follow-up for blood work. *Olanzapine* - While **olanzapine** is an effective atypical antipsychotic, it is not uniquely indicated for treatment-resistant cases in the same way clozapine is, nor does it typically require the intensive hematological monitoring. - Its main severe side effects are metabolic (e.g., weight gain, dyslipidemia), not **neutropenia** that would manifest in these lab results. *Chlorpromazine* - **Chlorpromazine** is a first-generation antipsychotic and, while effective, is not known for superior efficacy in treatment-resistant cases compared to clozapine and has a different side effect profile. - It can cause **agranulocytosis** but is not the drug of choice for treatment-resistant schizophrenia and its side effect profile does not align. *Haloperidol* - **Haloperidol** is a potent first-generation antipsychotic, effective for acute psychosis, but less effective for negative symptoms and carries a high risk of extrapyramidal side effects. - It is not typically chosen for treatment-resistant cases and does not cause the specific hematological issues seen in the lab results that would necessitate weekly follow-up for blood counts.

Question 167: A 60-year-old woman and her son are visited at her home by a health aid. He is her caregiver but has difficulty getting her out of the house. Her son is concerned about continuous and repetitive mouth and tongue movements that started about 2 weeks ago and have become more evident ever since. She is non-verbal at baseline and can complete most activities of daily living. She suffers from an unspecified psychiatric disorder. Her medications include fluphenazine. Today, her heart rate is 90/min, respiratory rate is 17/min, blood pressure is 125/87 mm Hg, and temperature is 37.0°C (98.6°F). On physical exam, she appears gaunt and anxious. She is drooling and her mouth is making a chewing motion that is occasionally disrupted by wagging her tongue back and forth. She seems to be performing these motions absentmindedly. Her heart has a regular rate and rhythm and her lungs are clear to auscultation bilaterally. CMP, CBC, and TSH are normal. A urine toxicology test is negative. What is the next best step in her management?

A. Reduce the dosage
B. Stop the medication (Correct Answer)
C. Start clozapine
D. Switch to chlorpromazine
E. Expectant management

Explanation: ***Stop the medication*** - The patient is presenting with symptoms of **tardive dyskinesia**, characterized by **involuntary, repetitive movements**, often involving the face (e.g., lip smacking, tongue protrusion, chewing motions), which are a known side effect of long-term use of **first-generation antipsychotics** like fluphenazine. - The recommended management for drug-induced tardive dyskinesia is to discontinue the offending medication if possible, especially given the severity and recent onset of symptoms. *Reduce the dosage* - While dosage reduction might be considered in some side effects, for established **tardive dyskinesia**, simply reducing the dose of the causative agent often does not halt the progression or alleviate symptoms effectively and may even worsen them in some cases. - The goal is to remove the underlying cause to prevent further neurological damage and potentially reverse the symptoms. *Start clozapine* - **Clozapine** is an atypical (second-generation) antipsychotic that is sometimes used in the management of severe tardive dyskinesia because it has a **lower risk of causing extrapyramidal symptoms** and can sometimes ameliorate existing ones. - However, the initial step should be to remove the offending agent (fluphenazine) before introducing a new medication, especially one with its own significant side effect profile like agranulocytosis. *Switch to chlorpromazine* - **Chlorpromazine** is also a **first-generation antipsychotic** and carries a significant risk of causing **extrapyramidal symptoms and tardive dyskinesia**, similar to fluphenazine. - Switching to another first-generation antipsychotic would not address the root cause of the tardive dyskinesia and would likely continue or worsen the symptoms. *Expectant management* - **Expectant management** (watching and waiting) is inappropriate for tardive dyskinesia because the condition can be **permanent** and worsen over time if the causative medication is continued. - Prompt intervention by discontinuing the culprit drug is crucial to prevent irreversible symptoms and improve the patient's quality of life.

Question 168: A 40-year-old woman comes to the physician because of a 2 week history of anorexia and a feeling of dryness in the mouth; she has had a 5.8-kg (12.8-lb) weight loss during this period. She also complains of fatigue and inability to carry out daily chores. One year ago, she was diagnosed with advanced cervical carcinoma, metastatic to the pancreas, and is being treated with combination chemotherapy. She is 157 cm (5 ft 2 in) tall and weighs 47 kg (103.6 lb); BMI is 19.1 kg/m2. She appears thin and pale. Her temperature is 37.7°C (99.8°F), blood pressure is 110/68 mm Hg, pulse is 105/min, and respirations are 28/min. There is generalized weakness and atrophy of the skeletal muscles. Which of the following is the most appropriate next step in management?

A. Cognitive behavioral therapy
B. Megestrol acetate (Correct Answer)
C. Mirtazapine
D. Cyproheptadine
E. Dronabinol

Explanation: ***Megestrol acetate*** - This patient exhibits signs of **cachexia** (anorexia, significant weight loss, fatigue, muscle atrophy) secondary to advanced cancer and chemotherapy. **Megestrol acetate** is a synthetic progestin that acts as an appetite stimulant and antigonadotropin, making it effective for treating **cancer-related anorexia-cachexia syndrome**. - It works by stimulating appetite and promoting weight gain, primarily by increasing fat mass, and is a **first-line agent** for this condition. *Cognitive behavioral therapy* - While beneficial for psychological stress or depression that might accompany cancer, **CBT** does not directly address the underlying physiological mechanisms of **cancer cachexia** or significantly improve appetite and weight loss. - Its primary role is in managing anxiety, mood disorders, and coping strategies, not as a primary treatment for **anorexia-cachexia syndrome**. *Mirtazapine* - **Mirtazapine** is an antidepressant that can cause **weight gain** as a side effect by increasing appetite, but its primary indication is for depression. - It is not the most appropriate first-line choice for severe cancer-related **anorexia-cachexia syndrome** compared to more potent appetite stimulants like megestrol acetate. *Cyproheptadine* - **Cyproheptadine** is a **first-generation antihistamine** with **serotonin antagonist** properties that can stimulate appetite, often used in cases of **failure to thrive** in children or in specific rare conditions. - However, it is generally considered less effective than megestrol acetate for treating **cancer-related cachexia** in adults and is associated with more sedative side effects. *Dronabinol* - **Dronabinol** is a **cannabinoid receptor agonist** that stimulates appetite and is primarily indicated for AIDS-related anorexia or chemotherapy-induced **nausea and vomiting**. - While it can improve appetite, **megestrol acetate** has demonstrated superior efficacy for weight gain and appetite stimulation in **cancer-related cachexia**, making it the preferred initial treatment.

Question 169: A 38-year-old woman presents to her primary care physician for evaluation of 3 months of increasing fatigue. She states that she feels normal in the morning, but that her fatigue gets worse throughout the day. Specifically, she says that her head drops when trying to perform overhead tasks. She also says that she experiences double vision when watching television or reading a book. On physical exam, there is right-sided ptosis after sustaining upward gaze for a 2 minutes. Which of the following treatments may be effective in treating this patient's diagnosis?

A. Chemotherapy
B. Vaccination
C. Thymectomy (Correct Answer)
D. Antitoxin
E. Riluzole

Explanation: ***Thymectomy*** - This patient's symptoms (fatigue worsening throughout the day, ptosis, diplopia, and head drop with overhead tasks) are classic for **myasthenia gravis (MG)**. Thymectomy is a definitive treatment option, especially for patients with a **thymoma** or generalized MG. - Approximately 10-15% of MG patients have a thymoma, and many others have thymic hyperplasia. **Thymectomy** can lead to remission or improvement in a significant number of patients by reducing the production of abnormal antibodies. *Chemotherapy* - Chemotherapy is primarily used for treating cancers and is not a first-line treatment for autoimmune diseases like **myasthenia gravis**. - While some immunosuppressants used in cancer may also be used in MG, chemotherapy, in its primary role, is not indicated for this condition. *Vaccination* - Vaccination is a preventive measure against infectious diseases and plays no role in the direct treatment of **myasthenia gravis**, which is an autoimmune disorder. - While MG patients should receive recommended vaccinations, these do not treat the underlying disease. *Antitoxin* - Antitoxins are used to neutralize toxins produced by bacteria, such as in **botulism** or **tetanus**. - Myasthenia gravis is an autoimmune disease involving antibodies against acetylcholine receptors, not a bacterial toxin. *Riluzole* - **Riluzole** is a medication approved for the treatment of **amyotrophic lateral sclerosis (ALS)**, a progressive neurodegenerative disease. - It works by reducing glutamate-mediated excitotoxicity and has no role in the pathophysiology or treatment of **myasthenia gravis**.

Question 170: An investigator is developing a drug that selectively inhibits the retrograde axonal transport of rabies virus towards the central nervous system. To achieve this effect, this drug must target which of the following?

A. Dynein (Correct Answer)
B. Tubulin
C. Nidogen
D. Kinesin
E. Acetylcholine

Explanation: ***Dynein*** - **Dynein** is a microtubule-dependent motor protein responsible for **retrograde axonal transport**, moving cargo (like rabies virus) away from the axon terminals towards the cell body and ultimately the central nervous system. - Inhibiting dynein would therefore prevent the **rabies virus** from traveling from the site of infection (e.g., muscle cell) to the central nervous system. *Tubulin* - **Tubulin** is the primary protein subunit that polymerizes to form **microtubules**, which serve as the tracks for axonal transport. - Inhibiting tubulin polymerization would disrupt both **anterograde** and **retrograde transport** nonspecifically, leading to severe neurotoxicity rather than selective inhibition of rabies virus transport. *Nidogen* - **Nidogen** (also known as entactin) is a glycoprotein component of the **basal lamina**, an extracellular matrix structure. - It plays a role in cell adhesion and tissue organization but is not directly involved in the intracellular motor processes of axonal transport. *Kinesin* - **Kinesin** is a microtubule-dependent motor protein primarily responsible for **anterograde axonal transport**, moving cargo from the cell body towards the axon terminals. - Inhibiting kinesin would disrupt the outward movement of vesicles and organelles, but would not prevent the **inward retrograde transport** of the rabies virus. *Acetylcholine* - **Acetylcholine** is a neurotransmitter that plays a role in synaptic transmission in both the peripheral and central nervous systems. - While rabies virus can affect neuronal function, acetylcholine itself is not a motor protein or a structural component directly involved in the physical process of **axonal transport**.

Question 171: A 63-year-old man comes to the physician for blurry vision and increased difficulty walking over the past month. He feels very fatigued after watering his garden but feels better after taking a nap. He has not had any recent illness. He has smoked one pack of cigarettes daily for 35 years. Examination shows drooping of the upper eyelids bilaterally and diminished motor strength in the upper extremities. Sensation to light touch and deep tendon reflexes are intact. An x-ray of the chest shows low lung volumes bilaterally. A drug with which of the following mechanisms of action is most appropriate for this patient?

A. Inhibition of acetylcholinesterase (Correct Answer)
B. Stimulation of D2 receptors
C. Regeneration of acetylcholinesterase
D. Inhibition of muscarinic ACh receptor
E. Stimulation of β2 adrenergic receptors

Explanation: ***Inhibition of acetylcholinesterase*** - The patient's symptoms (blurry vision, difficulty walking, fatigue improving with rest, ptosis, and proximal muscle weakness) are classic for **Lambert-Eaton myasthenic syndrome (LEMS)**, strongly associated with **small cell lung cancer** given his heavy smoking history and chest X-ray findings. - LEMS is caused by **autoantibodies against presynaptic voltage-gated calcium channels** at the neuromuscular junction, which **reduce acetylcholine release**. - While **3,4-diaminopyridine** (a potassium channel blocker that increases ACh release) is the preferred treatment for LEMS, it is not among the options; **acetylcholinesterase inhibitors** (e.g., pyridostigmine) can provide symptomatic benefit by increasing acetylcholine availability in the synaptic cleft, making this the best available option. - Note: Acetylcholinesterase inhibitors are more effective in **myasthenia gravis** than in LEMS, but may still provide modest improvement. *Incorrect: Stimulation of D2 receptors* - **D2 receptor agonists** (e.g., pramipexole, ropinirole) are used to treat **Parkinson's disease**, which presents with **resting tremor, rigidity, bradykinesia, and postural instability**. - The patient's fatigable weakness, ptosis, and improvement with rest are characteristic of a neuromuscular junction disorder, not a basal ganglia disorder. *Incorrect: Regeneration of acetylcholinesterase* - **Acetylcholinesterase reactivators** like **pralidoxime** are used to treat **organophosphate poisoning**, where acetylcholinesterase is irreversibly phosphorylated. - This patient has no history of pesticide exposure or cholinergic crisis symptoms (salivation, lacrimation, miosis, bronchospasm). *Incorrect: Inhibition of muscarinic ACh receptor* - **Muscarinic antagonists** (e.g., atropine, scopolamine) block parasympathetic effects and would **worsen neuromuscular transmission** by reducing cholinergic activity. - Blocking acetylcholine receptors would exacerbate the patient's muscle weakness and ptosis. *Incorrect: Stimulation of β2 adrenergic receptors* - **Beta-2 agonists** (e.g., albuterol, salmeterol) are bronchodilators used for **asthma and COPD**. - While the patient has a significant smoking history, his presentation is dominated by neuromuscular symptoms, not respiratory distress or bronchospasm.

Question 172: A 37-year-old woman presents with a 3-day history of fever. Past medical history is significant for chronic schizophrenia, managed with an antipsychotic medication. The patient has a low-grade fever and is slightly tachycardic. Physical examination is significant for the presence of tonsillar exudates. A CBC shows a markedly decreased WBC count. The patient’s antipsychotic medication is immediately discontinued. Which of the following is the antipsychotic medication that could have caused this problem?

A. Haloperidol
B. Risperidone
C. Olanzapine
D. Quetiapine
E. Clozapine (Correct Answer)

Explanation: ***Clozapine*** - **Clozapine** is well-known for its rare but severe side effect of **agranulocytosis**, characterized by a marked decrease in the white blood cell count, particularly neutrophils. - The patient's symptoms of fever, tonsillar exudates (indicating infection), and significantly decreased WBC count strongly suggest **agranulocytosis** induced by clozapine. *Haloperidol* - **Haloperidol** is a typical antipsychotic and is generally not associated with a high risk of agranulocytosis. - Its primary side effects often include **extrapyramidal symptoms** and QT prolongation. *Risperidone* - **Risperidone** is an atypical antipsychotic with a low association with agranulocytosis. - Common side effects include **sedation**, weight gain, and hyperprolactinemia. *Olanzapine* - While **olanzapine** is an atypical antipsychotic, it is not primarily associated with agranulocytosis, although it can cause other hematologic abnormalities rarely. - It is more commonly linked to **metabolic syndrome**, significant weight gain, and sedation. *Quetiapine* - **Quetiapine** is another atypical antipsychotic with a very low incidence of agranulocytosis. - Its frequent side effects include **sedation**, orthostatic hypotension, and weight gain.

Question 173: A 75-year-old woman with metastatic colon cancer comes to the physician requesting assistance in ending her life. She states: “I just can't take it anymore; the pain is unbearable. Please help me die.” Current medications include 10 mg oral hydrocodone every 12 hours. Her cancer has progressed despite chemotherapy and she is very frail. She lives alone and has no close family. Which of the following is the most appropriate initial action by the physician?

A. Consult with the local ethics committee
B. Submit a referral to psychiatry
C. Submit a referral to hospice care
D. Increase her pain medication dose (Correct Answer)
E. Initiate authorization of physician-assisted suicide

Explanation: ***Increase her pain medication dose*** - The patient's request to end her life is directly linked to "unbearable pain" and her current pain regimen (10 mg hydrocodone every 12 hours) is **sub-therapeutic** for metastatic cancer, indicating inadequate pain control. - Addressing the **underlying cause** of her distress, which is severe pain, with appropriate analgesia is the immediate and most ethical first step in palliative care. *Consult with the local ethics committee* - While ethical considerations are paramount in end-of-life care, this is not the **initial action** as the patient's pain, a modifiable factor, needs to be addressed first. - An ethics committee consultation would be more appropriate if adequate pain control has been attempted and the patient's request persists or if there are complex ethical dilemmas beyond immediate symptom management. *Submit a referral to psychiatry* - Although patients with severe illness may experience depression, the primary stated reason for her request is **unbearable pain**, which is a physical symptom requiring immediate medical attention. - A psychiatric referral might be warranted if, after adequate pain management, the patient continues to express persistent desires for death or exhibits symptoms of a treatable mood disorder, but it is not the *initial* step. *Submit a referral to hospice care* - This is an appropriate step for a patient with metastatic colon cancer and frailty, as hospice provides **comprehensive palliative care**. - However, the **immediate priority** is addressing her acute and inadequately treated pain, which is the stated reason for her distress and request for assistance in dying. *Initiate authorization of physician-assisted suicide* - Physician-assisted suicide is **illegal** in most jurisdictions and ethically controversial, and palliative care principles prioritize relieving suffering rather than ending life. - The patient's request stems from **unmanaged pain**, which is a treatable condition, making physician-assisted suicide an inappropriate and premature consideration.

Question 174: A 34-year-old woman comes to the physician with fever and malaise. For the past 2 days, she has felt fatigued and weak and has had chills. Last night, she had a temperature of 40.8°C (104.2°F). She has also had difficulty swallowing since this morning. The patient was recently diagnosed with Graves disease and started on methimazole. She appears uncomfortable. Her temperature is 38.3°C (100.9°F), pulse is 95/min, and blood pressure is 134/74 mm Hg. The oropharynx is erythematous without exudate. The lungs are clear to auscultation. Laboratory studies show: Hematocrit 42% Hemoglobin 13.4 g/dL Leukocyte count 3,200/mm3 Segmented neutrophils 9% Basophils < 1% Eosinophils < 1% Lymphocytes 79% Monocytes 11% Platelet count 230,000/mm3 Which of the following is the most appropriate next step in management?

A. Decrease methimazole dose
B. Discontinue methimazole (Correct Answer)
C. Switch to propylthiouracil
D. Test for EBV, HIV, and CMV
E. Bone marrow biopsy

Explanation: ***Discontinue methimazole*** - The patient's symptoms (fever, chills, sore throat, malaise) and laboratory findings (**leukopenia with severe neutropenia**, specifically only 9% segmented neutrophils leading to an absolute neutrophil count of 288/mm³) are highly concerning for **agranulocytosis**, a rare but serious side effect of methimazole. - **Agranulocytosis** is a life-threatening condition requiring immediate cessation of the offending drug to prevent severe infection and sepsis. *Decrease methimazole dose* - Reducing the dose is insufficient when **agranulocytosis** is suspected, as this condition warrants complete and immediate withdrawal of the drug. - Even low doses of methimazole can trigger or sustain **agranulocytosis** in susceptible individuals. *Switch to propylthiouracil* - Propylthiouracil (PTU) is another **thionamide** and carries a similar risk of inducing **agranulocytosis**, albeit potentially at a lower rate than methimazole. - Switching to another drug from the same class would not mitigate the risk and could exacerbate the current critical condition. *Test for EBV, HIV, and CMV* - While these viral infections can cause leukopenia, the acute onset of severe neutropenia in a patient recently started on **methimazole** makes drug-induced agranulocytosis the primary concern. - Investigating these viral causes would delay critical intervention for a more immediate and life-threatening drug reaction. *Bone marrow biopsy* - A bone marrow biopsy might confirm the diagnosis of **agranulocytosis** by showing myeloid hypoplasia or aplasia, but it is not the *most appropriate initial step*. - The immediate priority is to remove the suspected causative agent (methimazole) due to the high risk of infection associated with profound neutropenia.

Question 175: A 24-year-old man is taken to the emergency department by local law enforcement after they witnessed him physically assaulting a complete stranger. The officers report that they saw his eyes “moving back and forth quickly” and noted that he was very red-faced. The patient has no significant past medical or psychiatric history. His vital signs include: temperature 38.0°C (100.4°F), blood pressure 110/70 mm Hg, pulse 102/min, and respiratory rate 25/min. On physical examination, the patient is belligerent and refuses to cooperate during the examination. Rotary nystagmus is noted. Which of the following drugs would most likely be present in a urine toxicology screen from this patient?

A. Cocaine
B. Methamphetamine
C. Phencyclidine hydrochloride (PCP) (Correct Answer)
D. Lysergic acid diethylamide (LSD)
E. Marijuana

Explanation: ***Phencyclidine hydrochloride (PCP)*** - The patient's presentation with **belligerence**, **aggressiveness**, abnormal vital signs (tachycardia, tachypnea), and especially **rotary nystagmus** are classic signs of PCP intoxication. - PCP is known to cause severe behavioral disturbances, including unprovoked violence, along with characteristic neurological signs like nystagmus. *Cocaine* - While cocaine can cause **agitation**, **tachycardia**, and **hypertension**, it is less commonly associated with the severe **belligerence** and **rotary nystagmus** seen in this patient. - Cocaine intoxication typically presents with mydriasis, paranoia, and increased energy, but not typically the specific eye movements observed. *Methamphetamine* - Methamphetamine causes significant **sympathetic activation** leading to paranoia, **psychosis**, and agitation, similar to cocaine. - However, the presence of **rotary nystagmus** is not a characteristic feature of methamphetamine intoxication. *Lysergic acid diethylamide (LSD)* - LSD primarily causes **hallucinations**, perceptual distortions, and altered thought processes, often leading to **panic attacks** or a "bad trip." - It does not typically induce the severe **belligerence**, aggression, and **rotary nystagmus** described. *Marijuana* - Marijuana typically causes **euphoria**, relaxation, altered perception of time, and impaired motor coordination. - It does not cause the profound agitation, **belligerence**, or **rotary nystagmus** seen in this clinical scenario.

Question 176: You are called to the bedside of a 75-year-old woman, who is post-op day 4 from a right total hip replacement. The patient appears agitated; she is trying to pull out her IV, and for the past 4 hours she has been accusing the nursing staff of trying to poison her. Her family notes that this behavior is completely different from her baseline; she has not shown any signs of memory loss or behavioral changes at home prior to the surgery. You note that she still has an indwelling catheter. She continues on an opioid-based pain regimen. All of the following are potential contributors to the patient’s presentation EXCEPT:

A. Volume depletion
B. Infection
C. Electrolyte abnormalities
D. Amyloid accumulation (Correct Answer)
E. Polypharmacy

Explanation: ***Amyloid accumulation*** - **Amyloid accumulation** is associated with **Alzheimer's disease** and other forms of **dementia**, which are chronic neurodegenerative conditions. - The patient's acute onset of confusion and agitation, despite no prior history of cognitive decline, makes **amyloid accumulation** an unlikely immediate contributor to her current presentation. *Volume depletion* - **Dehydration** or **hypovolemia** can lead to reduced cerebral perfusion, altered mental status, and delirium in elderly patients. - Post-operative patients, especially those with pain and limited mobility, are at increased risk for **volume depletion** if fluid intake is inadequate or fluid losses are excessive. *Infection* - **Urinary tract infections (UTIs)** are common in elderly patients, particularly those with indwelling catheters, and can present as acute delirium or altered mental status without typical fever or dysuria. - The presence of an **indwelling catheter** makes a UTI a strong possibility for precipitating delirium in this patient. *Electrolyte abnormalities* - Disturbances in **electrolytes**, such as **hyponatremia** or **hypernatremia**, **hypokalemia**, or **hypercalcemia**, can profoundly affect brain function and lead to acute confusion, agitation, and delirium. - Post-operative fluid shifts, medication effects, and underlying medical conditions can predispose elderly patients to **electrolyte imbalances**. *Polypharmacy* - The use of multiple medications, particularly sedatives, analgesics (like **opioids**), and anticholinergics, is a significant risk factor for **delirium** in older adults. - Her current **opioid-based pain regimen** contributes to **polypharmacy** and poses a risk for drug-induced delirium.

Question 177: A 19-year-old woman comes to the physician because of increased sweating for the past 6 months. She experiences severe sweating that is triggered by stressful situations and speaking in public. She is failing one of her university classes because of her avoidance of public speaking. She has not had any fevers, chills, weight loss, or night sweats. Her temperature is 36.6°C (98°F). Physical examination shows moist skin in the axillae and on the palms, soles, and face. Which of the following drugs is most likely to be effective for this patient's condition?

A. Glycopyrrolate (Correct Answer)
B. Oxytocin
C. Physostigmine
D. Phenylephrine
E. Pilocarpine

Explanation: ***Glycopyrrolate*** - This patient presents with **primary focal hyperhidrosis**, characterized by excessive sweating without an underlying secondary cause, triggered by stress. - **Eccrine sweat glands** are under **cholinergic (muscarinic) control** via sympathetic postganglionic fibers that release acetylcholine. - **Glycopyrrolate** is an **anticholinergic drug** that works by blocking muscarinic receptors on sweat glands, thereby reducing sweat production. - It is particularly effective for **focal hyperhidrosis** affecting palms, soles, and axillae. *Oxytocin* - **Oxytocin** is a hormone primarily involved in **social bonding**, labor induction, and milk ejection. - It has no direct role in the regulation of sweat production or the treatment of hyperhidrosis. *Physostigmine* - **Physostigmine** is an **acetylcholinesterase inhibitor** that increases acetylcholine levels. - This would exacerbate sweating, as acetylcholine stimulates muscarinic receptors on sweat glands, leading to increased perspiration. *Phenylephrine* - **Phenylephrine** is an **α1-adrenergic agonist** primarily used as a vasoconstrictor and decongestant. - It acts on adrenergic receptors and does not directly affect the cholinergic pathways that control sweat gland activity. *Pilocarpine* - **Pilocarpine** is a **muscarinic agonist** that directly stimulates muscarinic receptors. - This would significantly increase sweating and salivation, making it unsuitable for treating hyperhidrosis.

Question 178: A 9-year-old girl is brought to the emergency room by her parents with severe shortness of breath, cough, and wheezing after playing with her friends in the garden. She has a history of bronchial asthma. Her vital signs are as follows: respiratory rate 39/min, pulse 121/min, blood pressure 129/67 mm Hg, and temperature 37.2°C (99°F). On physical exam, she looks confused and has bilateral diffuse wheezes on chest auscultation. Which of the following is the most appropriate drug to rapidly reverse her respiratory distress?

A. Inhaled cromolyn
B. Inhaled beclomethasone
C. Oral montelukast
D. Inhaled albuterol (Correct Answer)
E. Intravenous propranolol

Explanation: ***Inhaled albuterol*** - **Albuterol** is a **short-acting beta-2 adrenergic agonist (SABA)**, which provides rapid **bronchodilation** by relaxing the smooth muscles of the airways. - It is the **first-line treatment** for acute asthma exacerbations, effectively relieving **shortness of breath**, **cough**, and **wheezing**. *Inhaled cromolyn* - **Cromolyn** is a **mast cell stabilizer** used for **prophylactic** treatment of asthma, preventing the release of inflammatory mediators. - It has **no role** in the acute reversal of severe respiratory distress due to its delayed onset of action. *Inhaled beclomethasone* - **Beclomethasone** is an **inhaled corticosteroid (ICS)** used as a **controller medication** for long-term asthma management to reduce airway inflammation. - It is not indicated for acute symptom relief because its **anti-inflammatory effects** take several hours or days to manifest. *Oral montelukast* - **Montelukast** is a **leukotriene receptor antagonist** used for asthma prevention and treatment of **exercise-induced bronchoconstriction**. - Its onset of action is **too slow** to provide immediate relief for an acute and severe asthma exacerbation. *Intravenous propranolol* - **Propranolol** is a **non-selective beta-blocker**, which can cause **bronchoconstriction** and worsen asthma symptoms. - It is **contraindicated** in patients with asthma and would be dangerous to administer in this situation.

Question 179: Which of the following correctly pairs a neurotransmitter with its location of synthesis?

A. Serotonin -- Raphe nucleus (Correct Answer)
B. Acetylcholine -- Nucleus accumbens
C. GABA -- Ventral tegmentum
D. Norepinephrine -- Caudate nucleus
E. Dopamine -- Locus coeruleus

Explanation: ***Serotonin -- Raphe nucleus*** - The **raphe nuclei** are a group of serotonin-producing neurons located in the **brainstem**, crucial for mood, sleep, and appetite regulation. - **Serotonin** (5-HT) is synthesized from the amino acid **tryptophan** within these neurons. *Acetylcholine -- Nucleus accumbens* - **Acetylcholine** is primarily synthesized in the **basal forebrain (e.g., nucleus basalis of Meynert)** and the pontomesencephalic tegmental complex, not the nucleus accumbens. - The **nucleus accumbens** is a key structure in the reward pathway, receiving dopaminergic input from the ventral tegmental area. *GABA -- Ventral tegmentum* - **GABA** (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the brain, widely distributed and synthesized from **glutamate** by glutamic acid decarboxylase (GAD) in GABAergic neurons. - The **ventral tegmental area (VTA)** is primarily associated with **dopamine** synthesis and its release to the nucleus accumbens and prefrontal cortex. *Norepinephrine -- Caudate nucleus* - **Norepinephrine** is primarily synthesized in the **locus coeruleus**, a nucleus located in the pons, playing a role in arousal and attention. - The **caudate nucleus** is part of the basal ganglia, involved in motor control, learning, and memory, and is rich in **dopamine** receptors. *Dopamine -- Locus ceruleus* - **Dopamine** is mainly synthesized in the **substantia nigra** and the **ventral tegmental area (VTA)**, which project to various brain regions involved in motor control, reward, and motivation. - The **locus coeruleus** is the primary site for the synthesis of **norepinephrine**, not dopamine.

Question 180: A 49-year-old man presents to his primary care provider complaining of weakness and fatigue. He reports that he has started moving slower than normal and has noticed difficulty buttoning up his pants or tying his tie. He is accompanied by his wife who reports that he has started to move more slowly over the past 2 years. He has also become increasingly irritable and has had trouble sleeping. His past medical history is notable for hypertension, diabetes mellitus, and obesity. He takes enalapril and metformin. His family history is notable for multiple strokes in his mother and father. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 90/min, and respirations are 17/min. On exam, strength is 4+/5 bilaterally in his upper extremities and 4/5 in his lower extremities. Some muscle atrophy is noted in his legs and feet. Patellar reflexes are 3+ bilaterally. He has a tremor in his right hand that diminishes when he is instructed to hold a pen in his hand. He is oriented to person, place and time. He states that he feels depressed but denies suicidal ideation. His physician prescribes multiple medications including a drug that is also indicated in the treatment of prolactinomas. Which of the following is the mechanism of action of this medication?

A. Activate dopamine receptors (Correct Answer)
B. Inhibit dopamine receptors
C. Prevent dopamine degradation into 3-O-methyldopa
D. Prevent dopamine degradation into 3,4-dihydroxyphenylacetic acid
E. Increase dopamine release

Explanation: ***Activate dopamine receptors*** - The patient's symptoms (tremor, slowness of movement, difficulty with fine motor tasks, fatigue, irritability, sleep trouble) along with the physician prescribing a medication concurrently used for **prolactinomas** strongly suggest **Parkinson's disease**, which is characterized by **dopamine deficiency**. - Medications for Parkinson's disease that also treat prolactinomas (e.g., **bromocriptine**, **cabergoline**) are **dopamine agonists** that directly activate dopamine receptors. *Inhibit dopamine receptors* - Inhibiting dopamine receptors would worsen the symptoms of **Parkinson's disease**, as the disease is caused by a **deficiency in dopamine**. - Antipsychotic medications, which inhibit dopamine receptors, are typically contraindicated in Parkinson's patients due to their potential to exacerbate motor symptoms. *Prevent dopamine degradation into 3-O-methyldopa* - This mechanism describes the action of **catechol-O-methyltransferase (COMT) inhibitors**, which prevent the breakdown of levodopa (a dopamine precursor) into 3-O-methyldopa. - While used in Parkinson's disease, COMT inhibitors do not directly activate dopamine receptors and are not typically indicated for **prolactinomas**. *Prevent dopamine degradation into 3,4-dihydroxyphenylacetic acid* - This mechanism describes the action of **monoamine oxidase-B (MAO-B) inhibitors** (e.g., selegiline, rasagiline), which prevent the breakdown of dopamine into 3,4-dihydroxyphenylacetic acid (DOPAC). - While MAO-B inhibitors are used in Parkinson's disease, they are not indicated for the treatment of **prolactinomas**. *Increase dopamine release* - While some drugs can increase dopamine release (e.g., **amantadine**), this is not the primary mechanism of medications used for both **Parkinson's disease** and **prolactinomas**. - The most direct action relevant to treating both conditions is the direct activation of **dopamine receptors** by agonists.

Question 181: A 21-year-old woman comes to the physician because of a 4-month history of fatigue. She admits to binge eating several times per month, after which she usually induces vomiting for compensation. She exercises daily in an effort to lose weight. She is 168 cm (5 ft 6 in) tall and weighs 60 kg (132 lb); BMI is 21.3 kg/m2. Physical examination shows calluses on the knuckles and bilateral parotid gland enlargement. Oropharyngeal examination shows eroded dental enamel and decalcified teeth. Which of the following is the most appropriate pharmacotherapy for this patient's condition?

A. Venlafaxine
B. Orlistat
C. Mirtazapine
D. Buspirone
E. Fluoxetine (Correct Answer)

Explanation: ***Fluoxetine*** - **Fluoxetine** is the **first-line antidepressant** approved for the treatment of **bulimia nervosa**, especially at higher doses (e.g., 60 mg/day). - It helps reduce the frequency of **binge eating** and **purging behaviors** and can also address co-occurring mood symptoms. *Venlafaxine* - **Venlafaxine** is an SNRI (serotonin-norepinephrine reuptake inhibitor) primarily used for **major depression** and **generalized anxiety disorder**. - While effective for depression, it is not specifically recommended as first-line pharmacotherapy for **bulimia nervosa**. *Orlistat* - **Orlistat** is a **lipase inhibitor** used for weight loss by reducing dietary fat absorption. - It is not indicated for the treatment of **bulimia nervosa** and could potentially worsen the patient's anxiety about weight and body image. *Mirtazapine* - **Mirtazapine** is an antidepressant that works by blocking alpha-2 adrenergic receptors and serotonin receptors, often used for **depression** and difficulties with **insomnia** or **poor appetite**. - It is not the primary pharmacotherapeutic choice for **bulimia nervosa**, and its weight-gain side effect might be counterproductive in this context. *Buspirone* - **Buspirone** is an **anxiolytic** agent used to treat **generalized anxiety disorder**. - It does not have established efficacy for core **bulimic symptoms** (binge eating, purging) or depression, making it less appropriate as a primary treatment.

Question 182: A 40-year-old woman comes to the physician for a preoperative examination before undergoing a planned elective cholecystectomy. She has a history of myasthenia gravis, for which she takes oral pyridostigmine. She has had occasional episodes of muscle weakness, blurred vision, and slurred speech recently. Physical examination shows mild ptosis bilaterally. The pupils are normal in size and reactive bilaterally. Muscle strength is 3/5 at the hips and shoulders. Sensory examination shows no abnormalities. After the administration of 10 mg of edrophonium, her ptosis resolves, and her proximal muscle strength improves to 5/5. This patient is most likely to benefit from which of the following interventions?

A. Initiate treatment with intravenous atropine
B. Increase the dose of pyridostigmine (Correct Answer)
C. Add glycopyrrolate as needed
D. Administer timed doses of edrophonium
E. Discontinue treatment with pyridostigmine

Explanation: ***Increase the dose of pyridostigmine*** - The rapid improvement in symptoms (ptosis resolution, improved muscle strength) after **edrophonium** administration indicates a **myasthenic crisis** or under-dosing of pyridostigmine. - Edrophonium is a short-acting **acetylcholinesterase inhibitor**, and its positive effect suggests that the patient needs more acetylcholine at the neuromuscular junction, which can be achieved by increasing the dose of the long-acting acetylcholinesterase inhibitor, pyridostigmine. *Initiate treatment with intravenous atropine* - **Atropine** is an **anticholinergic** agent used to treat cholinergic crisis, which presents paradoxically with increased weakness but also severe muscarinic side effects (e.g., salivation, bradycardia, diarrhea). - The positive response to edrophonium rules out cholinergic crisis; administering atropine would worsen the myasthenic symptoms. *Add glycopyrrolate as needed* - **Glycopyrrolate** is another **anticholinergic** agent, similar to atropine, often used to reduce muscarinic side effects associated with acetylcholinesterase inhibitors. - While it may help with side effects, it would not address the underlying muscle weakness due to insufficient acetylcholine in myasthenia gravis and could exacerbate it. *Administer timed doses of edrophonium* - **Edrophonium** is a **very short-acting** drug with a half-life of only a few minutes, making it unsuitable for long-term therapeutic management of myasthenia gravis. - Its primary use is diagnostic (Tensilon test) or to differentiate between myasthenic and cholinergic crises, not for chronic treatment. *Discontinue treatment with pyridostigmine* - **Pyridostigmine** is the mainstay treatment for myasthenia gravis, improving muscle strength by increasing acetylcholine at the neuromuscular junction. - Discontinuing it would inevitably lead to a severe worsening of myasthenic symptoms, as the patient is clearly under-treated, not over-treated.

Question 183: A 12-year-old girl is brought to the pediatrician by her father who is concerned about the child’s ability to sit in a moving vehicle. She frequently develops nausea and dizziness when riding in a car for more than 10 minutes. The child has vomited twice over the past month while riding in the car. Her symptoms are significantly impairing her ability to make it to school on time without having to stop and get out of the car. The child does well in school and has several close friends. On examination, the child is well-appearing and appropriately interactive. Dix-Hallpike maneuver is negative. Her gait is normal. Strength and range of motion are full and symmetric bilaterally in the upper and lower extremities. The father would like to know if there is anything his daughter can take to be able to sit in a moving vehicle without feeling ill. A medication with which of the following mechanisms of action is indicated to manage this patient’s symptoms?

A. Muscarinic acetylcholine receptor antagonist (Correct Answer)
B. Beta-1 adrenergic receptor agonist
C. Nicotinic acetylcholine receptor agonist
D. Alpha-2 adrenergic receptor agonist
E. Dopamine receptor antagonist

Explanation: ***Muscarinic acetylcholine receptor antagonist*** - The patient's symptoms are consistent with **motion sickness**, which is primarily mediated by the **vestibular system** and involves **acetylcholine** and **histamine** pathways. - **Anticholinergic drugs**, such as **scopolamine**, block muscarinic acetylcholine receptors, effectively reducing nausea and vomiting associated with motion sickness. - Scopolamine is considered one of the most effective medications for motion sickness prophylaxis. *Beta-1 adrenergic receptor agonist* - **Beta-1 adrenergic receptor agonists** (e.g., dobutamine) increase heart rate and myocardial contractility and are used for conditions like **heart failure** or **cardiogenic shock**. - They do not have a role in treating motion sickness or its associated nausea and dizziness. *Nicotinic acetylcholine receptor agonist* - **Nicotinic acetylcholine receptor agonists** (e.g., nicotine) act on autonomic ganglia and the neuromuscular junction. - These agents are not indicated for motion sickness and could potentially worsen symptoms or cause other adverse effects. *Alpha-2 adrenergic receptor agonist* - **Alpha-2 adrenergic receptor agonists** (e.g., clonidine) are used to treat **hypertension** and **ADHD** due to their central sympatholytic effects. - They are not effective for motion sickness and would not alleviate the described symptoms. *Dopamine receptor antagonist* - While some **dopamine receptor antagonists** (e.g., promethazine, metoclopramide) have antiemetic properties, their efficacy in motion sickness is primarily due to **antihistamine activity** (H1 receptor blockade) rather than dopamine antagonism. - **Anticholinergics** (muscarinic antagonists) are more direct and effective for motion sickness as they specifically target the vestibular-acetylcholine pathway that mediates motion-induced nausea. - Pure dopamine antagonists without antihistamine effects would not be the primary choice for this condition.

Question 184: A 67-year-old farmer presents to the emergency department with a chief complaint of unusual behavior. His wife states that since this morning he has experienced dryness and flushing of his skin while working outside. As the day went on, the patient found it exceedingly difficult to urinate and had to create significant abdominal pressure for a weak stream of urine to be produced. Currently, the patient seems confused and responds incoherently. The patient has a past medical history of Parkinson's disease, alcohol abuse, irritable bowel syndrome, anxiety, diabetes mellitus, hypertension, constipation and a suicide attempt when he was 23 years old. He is currently taking lisinopril, hydrochlorothiazide, metformin, insulin, benztropine, levodopa/carbidopa, and vitamin C. The only other notable symptoms this patient has experienced are recent severe seasonal allergies. On physical exam you note dry, flushed skin, and a confused gentleman. His temperature is 99.5°F (37.5°C), pulse is 112/min, blood pressure is 130/90 mmHg, respirations are 18/min, and oxygen saturation is 96% on room air. Lab values are ordered. Which of the following is the most likely cause of this patient's presentation?

A. Medication (Correct Answer)
B. Heat stroke
C. Alcohol
D. Infection
E. Insecticide exposure

Explanation: ***Medication*** - The patient's symptoms (dry skin, flushed skin, confusion, urinary retention, tachycardia) are consistent with **anticholinergic toxicity**, which can result from an overdose or accumulation of anticholinergic medications. - The patient is taking **benztropine**, an anticholinergic used for Parkinson's disease, and experiencing severe seasonal allergies, suggesting he might have started taking an **over-the-counter antihistamine** (many of which have anticholinergic effects) which in combination with benztropine, could lead to toxicity. *Heat stroke* - While **flushed, dry skin** and **confusion** can occur in heat stroke, the patient's temperature (99.5°F) is not elevated enough to suggest heat stroke. - The patient's significant **urinary retention** is not a primary or typical symptom of heat stroke. *Alcohol* - The patient has a history of alcohol abuse, but the described symptoms are not typical of acute alcohol intoxication or withdrawal, especially the prominent **dry skin**, **flushing**, and **urinary retention**. - There is no mention of recent alcohol consumption or specific withdrawal symptoms like tremors or seizures. *Infection* - While **confusion** can be a symptom of infection, especially in the elderly, the constellation of other symptoms (**dry skin, flushed skin, urinary retention, tachycardia**) does not specifically point to a common infection. - The patient's temperature is only mildly elevated, not strongly indicative of a severe infection. *Insecticide exposure* - Exposure to **organophosphate insecticides** would typically cause **cholinergic crisis**, characterized by symptoms like increased salivation, lacrimation, urination, defecation, gastrointestinal upset, and emesis (SLUDGE syndrome), which are the opposite of the patient's anticholinergic symptoms. - There is no information suggesting exposure to insecticides, and the clinical picture does not align with cholinergic toxicity.

Question 185: A 70-year-old woman is brought to her physician by her daughter who reports that the patient has been increasingly confused and forgetful over the past year. The daughter reports that the patient has difficulty finding words, remembering names, and maintaining a conversation. She has gotten lost twice while driving. Her past medical history is known for obesity, diabetes, and atrial fibrillation. She takes metformin, glyburide, and warfarin. She drinks socially and has a 30 pack-year smoking history. Her family history is notable for Parkinson’s disease in her father and stroke in her mother. A head CT demonstrates sulcal widening and narrowing of the gyri. The physician decides to start the patient on a medication known to inhibit a cell surface glutamate receptor. Which of the following is a downstream effect of this medication?

A. Increased intracellular sodium
B. Decreased intracellular acetylcholine
C. Increased intracellular acetylcholine
D. Increased intracellular calcium
E. Decreased intracellular calcium (Correct Answer)

Explanation: ***Decreased intracellular calcium*** - The patient's symptoms (confusion, forgetfulness, difficulty finding words, getting lost while driving) and imaging findings (sulcal widening, gyral narrowing) are consistent with **Alzheimer's disease**. - The medication described, which inhibits a **cell surface glutamate receptor**, is likely **memantine**. Memantine is an **NMDA receptor antagonist**, which works by blocking the excessive influx of **calcium** into neurons and thus preventing **excitotoxicity**. *Increased intracellular sodium* - While **NMDA receptor activation** does lead to an influx of **sodium** (and calcium), memantine's primary mechanism of action targets the prevention of excessive **calcium influx** to mitigate excitotoxicity. Blocking the NMDA receptor might lead to a slight decrease in sodium influx, but the most clinically relevant target of memantine for preventing neuronal damage is calcium. - Ion channels like the **NMDA receptor** allow the passage of multiple ions, but specific therapeutic interventions often focus on the ion whose dysregulation is most detrimental in the disease state. *Decreased intracellular acetylcholine* - Alzheimer's disease is characterized by a **deficiency in acetylcholine**, and many medications (like cholinesterase inhibitors) aim to *increase* acetylcholine levels. - Memantine's mechanism of action does not directly involve the modulation of **acetylcholine** levels; it primarily affects the glutamatergic system. *Increased intracellular acetylcholine* - While therapies for Alzheimer's disease often aim to **increase acetylcholine** (e.g., donepezil, rivastigmine), this is not the mechanism of action of the medication described (a glutamate receptor inhibitor). - Memantine targets the **glutamatergic system**, specifically the NMDA receptor, rather than cholinergic pathways. *Increased intracellular calcium* - In Alzheimer's disease, **excessive intracellular calcium** influx through NMDA receptors is a key contributor to **excitotoxicity** and neuronal damage. - The described medication (memantine) works by *blocking* these receptors, thereby *reducing* the influx of calcium, not increasing it.

Question 186: A healthy mother gives birth to a child at 40 weeks of gestation. On examination, the child has ambiguous genitalia. A karyotype analysis reveals the presence of a Y chromosome. Additional workup reveals the presence of testes and a normal level of serum luteinizing hormone (LH) and testosterone. Which of the following is the most likely cause of this patient’s condition?

A. Failed migration of neurons producing gonadotropin releasing hormone (GnRH)
B. Androgen receptor deficiency
C. 5-alpha reductase deficiency (Correct Answer)
D. Aromatase deficiency
E. Presence of two X chromosomes

Explanation: ***5-alpha reductase deficiency*** - This condition involves the inability to convert **testosterone** to the more potent **dihydrotestosterone (DHT)**, which is essential for external male genital development. - The presence of **testes**, Y chromosome, and normal testosterone levels indicate proper testicular function but impaired peripheral androgen action on external genitalia, leading to **ambiguous genitalia**. *Failed migration of neurons producing gonadotropin releasing hormone (GnRH)* - This describes **Kallmann syndrome**, which typically presents with **hypogonadotropic hypogonadism** (low LH and testosterone), as well as anosmia. - The patient's normal LH and testosterone levels rule out this condition. *Androgen receptor deficiency* - This would result in **androgen insensitivity syndrome (AIS)**, where cells cannot respond to androgen, despite normal or high levels of testosterone. - Patients with complete AIS typically present with female external genitalia, blind vaginal pouch, absent uterus, and develop testes. However, the presence of ambiguous genitalia points more towards a partial effect, which can also be seen in AIS, but 5-alpha reductase deficiency more specifically captures the scenario of impaired external masculinization with normal internal male structures. *Aromatase deficiency* - This would typically lead to impaired conversion of androgens to estrogens, resulting in **virilization** in affected individuals (e.g., males presenting with tall stature and osteoporosis, females with virilization and primary amenorrhea). - It would not cause ambiguous genitalia with normal testosterone and LH levels. *Presence of two X chromosomes* - A karyotype showing a Y chromosome has already ruled out the presence of two X chromosomes, which is characteristic of biological females. - If a Y chromosome is present along with two X chromosomes (e.g., **Klinefelter syndrome**, XXY), it typically results in male appearance with **hypogonadism** and **gynecomastia**, but not ambiguous genitalia from birth if all sex-determining genes are functional.

Question 187: A 55-year-old college professor with a long-standing history of neuropathic pain presents to a medical clinic with weight loss and early morning awakening for the past several months. She feels as if she has no energy to go about her work. She complains that she is not as focused at work or home as she used to be and finds both her life and work unfulfilling. She has had these symptoms for the past 2 months. She was started on antidepressants in the past, but the antidepressants did not provide any significant improvement. She eventually improved and has been in remission for almost 1 year now. She would really like a simple treatment option to address both her neuropathic pain and her depression, and she is started on a tricyclic antidepressant. What safety advice is most important for this patient’s treatment plan?

A. The medication has a very short half-life.
B. The medication can cause agranulocytosis.
C. The medication can lower the seizure threshold.
D. This medication can be lethal at high doses. (Correct Answer)
E. The medication can cause serotonin syndrome.

Explanation: ***This medication can be lethal at high doses.*** - **Tricyclic antidepressants (TCAs)** have a narrow therapeutic index, meaning the difference between a therapeutic dose and a toxic dose is small, making them particularly dangerous in overdose. - Due to their effects on cardiac ion channels, **overdoses can cause fatal arrhythmias** such as ventricular tachycardia and fibrillation, as well as seizures and coma. *The medication has a very short half-life.* - **TCAs typically have long half-lives**, often requiring once-daily dosing, which contradicts the statement that they have a very short half-life. - A short half-life would mean the drug is quickly eliminated, not a primary safety concern for accidental or intentional overdose with TCAs. *The medication can cause agranulocytosis.* - **Agranulocytosis is a rare but severe side effect more commonly associated with antipsychotics** (e.g., clozapine) or certain antiepileptic drugs, not a typical or prominent side effect of TCAs. - While all medications carry some risk of hematologic abnormalities, agranulocytosis is not a primary safety warning for TCAs. *The medication can lower the seizure threshold.* - While TCAs can indeed **lower the seizure threshold**, especially at higher doses or in susceptible individuals, the most critical safety concern leading to lethality in overdose is their cardiotoxicity. - Seizures are a serious side effect, but **fatal cardiac arrhythmias** are the leading cause of death in TCA overdose. *The medication can cause serotonin syndrome.* - **Serotonin syndrome is a risk when TCAs are combined with other serotonergic agents** (e.g., SSRIs, MAOIs) due to additive effects on serotonin levels. - However, in the context of a single TCA prescription, the most immediate and profound safety concern, especially regarding potential lethality at high doses, is not serotonin syndrome but rather cardiotoxicity.

Question 188: A high-throughput screen to identify new sympathomimetic compounds was developed such that a transgenic line of cells was created that contained the alpha-1 (red), alpha-2 (yellow), beta-1 (green) and beta-2 (blue) receptors. When each of the receptors was activated a different fluorescent protein was expressed and new compounds with different properties could be identified by the fluorescence that they induced. Compound 7583 selectively induced the expression of the blue fluorescent protein. Which of the following known sympathomimetic medications if administered would similarly result in expression of only the blue fluorescent protein?

A. Albuterol (Correct Answer)
B. Fenoldopam
C. Epinephrine
D. Isoproterenol
E. Midodrine

Explanation: ***Albuterol*** - The blue fluorescent protein is expressed upon activation of the **beta-2 receptor**. Albuterol is a **selective beta-2 adrenergic agonist**. - Its primary clinical use is as a **bronchodilator** in asthma and COPD, acting by relaxing bronchial smooth muscle via beta-2 receptor activation. *Fenoldopam* - Fenoldopam is a **D1 dopamine receptor agonist** used as a rapid-acting vasodilator. - It has **no significant direct activity** at adrenergic alpha or beta receptors. *Epinephrine* - Epinephrine is a **non-selective adrenergic agonist** that activates alpha-1, alpha-2, beta-1, and beta-2 receptors. - It would induce the expression of **all four fluorescent proteins** (red, yellow, green, and blue). *Isoproterenol* - Isoproterenol is a **non-selective beta-adrenergic agonist**, activating both beta-1 and beta-2 receptors. - It would induce the expression of **green and blue fluorescent proteins**, but not exclusively blue. *Midodrine* - Midodrine is a **selective alpha-1 adrenergic agonist** and would induce the expression of the **red fluorescent protein**. - It is primarily used to treat **orthostatic hypotension** by causing vasoconstriction.

Question 189: A 53-year-old man is brought by his daughter to the clinic. She lives a town away but visits often. She reports that on recent visits, his mood has been volatile, ranging from aggressive at some moments to depressed at others. She has noticed some new jerky movements which she has never seen before and has been quite forgetful. She is concerned that he might be abusing alcohol and drugs. What changes would you expect in the brain of this patient?

A. Decreased GABA at the caudate (Correct Answer)
B. Increased acetylcholine at the caudate
C. Decreased dopamine at the ventral tegmentum and substantia nigra pars compacta
D. Increased norepinephrine at the locus ceruleus
E. Decreased serotonin at the raphe nucleus

Explanation: ***Decreased GABA at the caudate*** - The patient's symptoms of **mood volatility**, **jerky movements (chorea)**, and **forgetfulness** are classic signs of Huntington's disease. - Huntington's disease is characterized by the degeneration of **GABAergic neurons** in the **caudate nucleus** and putamen, leading to reduced inhibitory neurotransmission. *Increased acetylcholine at the caudate* - Huntington's disease is associated with **selective neuronal loss**, primarily of GABAergic neurons, not an increase in acetylcholine. - While acetylcholine plays a role in movement, its increase in the caudate is not the primary pathology seen in Huntington's disease. *Decreased dopamine at the ventral tegmentum and substantia nigra pars compacta* - This description is characteristic of **Parkinson's disease**, where there is degeneration of dopaminergic neurons in the substantia nigra pars compacta. - Parkinson's typically presents with **bradykinesia**, **rigidity**, and **tremor**, which are distinct from the patient's choreiform movements. *Increased norepinephrine at the locus ceruleus* - The locus ceruleus is a primary source of **norepinephrine** in the brain, playing a role in attention, arousal, and mood. - Conditions involving altered norepinephrine levels in the locus ceruleus are not typically associated with the chorea and specific cognitive decline seen in this patient. *Decreased serotonin at the raphe nucleus* - The raphe nuclei are the main source of **serotonin** in the brain, involved in mood regulation, sleep, and appetite. - While mood disturbances are present, decreased serotonin from the raphe nucleus is more typically associated with conditions like **depression**, and does not explain the characteristic chorea.

Question 190: A 61-year-old man with Alzheimer disease is brought to the emergency department 20 minutes after ingesting an unknown amount of his medications in a suicide attempt. He reports abdominal cramps, diarrhea, diaphoresis, and muscular weakness and spasms in his extremities. His temperature is 38.4°C (101.1°F), pulse is 51/min, respirations are 12/min and labored, and blood pressure is 88/56 mm Hg. Physical examination shows excessive salivation and tearing, and small pupils bilaterally. Treatment with atropine is initiated. Shortly after, most of his symptoms have resolved, but he continues to have muscular spasms. Administration of which of the following is the most appropriate next step in management of this patient?

A. Carbachol
B. Pancuronium
C. Benztropine
D. Physostigmine
E. Pralidoxime (Correct Answer)

Explanation: ***Pralidoxime*** - The patient's symptoms (abdominal cramps, diarrhea, diaphoresis, muscular weakness and spasms, bradycardia, hypotension, salivation, tearing, miosis) are consistent with **cholinergic toxicity** from overdose of cholinesterase inhibitor medications used for Alzheimer disease (e.g., donepezil, rivastigmine, galantamine). While atropine blocks muscarinic receptors and resolves many symptoms (salivation, diarrhea, bradycardia), it does not reverse the **nicotinic effects** (muscular spasms, weakness). - Pralidoxime is a **cholinesterase reactivator** that works by detaching the inhibitor from acetylcholinesterase, restoring its function and reversing both muscarinic and nicotinic effects, especially the persistent muscular spasms. *Carbachol* - Carbachol is a **direct cholinergic agonist** that acts on both muscarinic and nicotinic receptors. Administering carbachol would worsen the existing cholinergic toxicity. - It is used for conditions like glaucoma or postoperative urinary retention, not for treating cholinergic poisoning. *Pancuronium* - Pancuronium is a **nondepolarizing neuromuscular blocker** that prevents acetylcholine from binding to nicotinic receptors at the neuromuscular junction, causing muscle paralysis. - While it would stop muscular spasms by inducing paralysis, it would not address the underlying cholinergic excess and would necessitate ventilatory support while the patient is already experiencing labored breathing. This is an inappropriate primary treatment for cholinesterase inhibitor overdose. *Benztropine* - Benztropine is an **anticholinergic agent** primarily used to treat Parkinson's disease and drug-induced extrapyramidal symptoms. - While it has anticholinergic effects, its primary action is not potent enough to reverse severe cholinergic crisis, particularly the muscarinic effects already treated by atropine or the nicotinic effects causing spasms. *Physostigmine* - Physostigmine is a **reversible cholinesterase inhibitor** that increases acetylcholine levels at the synapse. - This medication would exacerbate the patient's severe cholinergic poisoning, leading to a worsening of symptoms, and is contraindicated in this scenario.

Question 191: A 32-year-old man comes to the physician with involuntary lip smacking and hand and leg movements for the past two weeks. The movements are causing him difficulty walking and functioning at work. He has bipolar disorder treated with fluphenazine. Three months ago, he was hospitalized because of a manic episode, and his dosage was adjusted. Since then, he has not experienced a depressed mood, increased energy, irritability, or a change in his eating or sleeping patterns. He does not have suicidal or homicidal ideation. His temperature is 37.2°C (99°F), pulse is 75/min, and blood pressure is 126/78 mmHg. Examination shows repetitive lip smacking and dance-like hand and leg movements. His speech is not pressured, and his affect is appropriate. He is switched from fluphenazine to risperidone and his symptoms improve. Which of the following mechanisms explains this patient's improvement?

A. Weaker acetylcholine antagonism
B. Weaker serotonin antagonism
C. Weaker dopamine antagonism (Correct Answer)
D. Weaker acetylcholine agonism
E. Weaker histamine antagonism

Explanation: ***Weaker dopamine antagonism*** - The patient's symptoms (involuntary lip smacking, dance-like hand and leg movements) are consistent with **tardive dyskinesia**, a side effect of **long-term antipsychotic use**, particularly **first-generation antipsychotics** like fluphenazine. - Tardive dyskinesia is thought to be caused by **hypersensitivity of dopamine receptors** in the basal ganglia due to prolonged dopamine receptor blockade. Switching to a **second-generation antipsychotic** like risperidone, which has weaker D2 antagonism, reduces this effect and can improve symptoms. *Weaker acetylcholine antagonism* - While fluphenazine has some anticholinergic effects, **acetylcholine antagonism** is primarily associated with side effects such as dry mouth, constipation, and blurred vision, not tardive dyskinesia. - Stronger acetylcholine antagonism by antipsychotics can sometimes reduce **extrapyramidal symptoms (EPS)**, but tardive dyskinesia involves dopamine receptor changes. *Weaker serotonin antagonism* - Many antipsychotics, especially second-generation ones like risperidone, have **serotonin (5-HT2A) antagonism**, which is thought to contribute to their lower risk of EPS and better efficacy for negative symptoms. - However, serotonin antagonism is not the primary mechanism by which risperidone improves tardive dyskinesia induced by potent D2 antagonism. *Weaker acetylcholine agonism* - **Acetylcholine agonism** is not a primary mechanism of action for typical or atypical antipsychotics. - Medications that increase cholinergic activity might worsen some extrapyramidal symptoms, but this is not relevant to the improvement in tardive dyskinesia from switching to risperidone. *Weaker histamine antagonism* - Some antipsychotics, like olanzapine or quetiapine, have significant **histamine (H1) antagonism**, leading to side effects such as sedation and weight gain. - However, histamine antagonism is not directly linked to the pathogenesis or improvement of tardive dyskinesia.

Question 192: A 28-year-old man is brought to the emergency department after his girlfriend found him twitching and jerking in the yard while gardening. Shortly after he became obtunded, emergency medical services reported 1 episode of emesis during transport. His blood pressure is 85/50 mmHg, pulse is 55/min, and respirations are irregular. Physical examination demonstrates marks on his left forearm, pinpoint pupils, diaphoresis, and fasciculations of his left calf. Following initial stabilization and respiratory support, what is the best next step?

A. Atropine
B. Naltrexone
C. Atropine and pralidoxime (Correct Answer)
D. Lamotrigine
E. Naloxone

Explanation: ***Atropine and pralidoxime*** * This patient presents with a classic picture of **organophosphate poisoning**, characterized by profuse secretions, bradycardia, hypotension, pinpoint pupils, and fasciculations. * **Atropine** is given to block the muscarinic effects, and **pralidoxime** (2-PAM) is used to reactivate acetylcholinesterase, reversing both muscarinic and nicotinic effects. * *Atropine* * While essential for managing the **muscarinic effects** like bradycardia and profuse secretions, atropine alone does not address the nicotinic effects, such as muscle fasciculations and weakness. * Without pralidoxime, the underlying cause of acetylcholinesterase inhibition is not treated, potentially leading to continued nicotinic toxicity. * *Naltrexone* * **Naltrexone** is an opioid receptor antagonist used for opioid dependence and alcohol use disorder. * It has no role in the management of organophosphate poisoning, which involves cholinergic overstimulation. * *Lamotrigine* * **Lamotrigine** is an anticonvulsant medication used to treat epilepsy and bipolar disorder. * The patient's seizures are secondary to organophosphate poisoning and would not be primarily managed with lamotrigine. * *Naloxone* * **Naloxone** is an opioid antagonist used to reverse opioid overdose. * The patient's symptoms are inconsistent with opioid overdose and point strongly towards cholinergic crisis.

Question 193: A 72-year-old man comes to the physician with his son for a follow-up examination. The son reports that his father's mental status has declined since the previous visit when he was diagnosed with Alzheimer dementia. The patient often begins tasks and forgets what he was doing. He has increased trouble remembering events that occurred the day before and sometimes forgets names of common household objects. He has hypertension and hyperlipidemia. His current medications include lisinopril, hydrochlorothiazide, atorvastatin, and donepezil. He is confused and oriented only to person. He is unable to count serial sevens backward from 100. He is able to register 3 items but unable to recall them 5 minutes later. Which of the following is the most appropriate pharmacotherapy?

A. Memantine (Correct Answer)
B. Ginkgo biloba
C. Risperidone
D. Citalopram
E. Vitamin E

Explanation: ***Memantine*** - The patient exhibits features of **moderate to severe Alzheimer's disease**, as evidenced by significant cognitive decline and inability to recall items. Donepezil (an acetylcholinesterase inhibitor) is already being used; **memantine**, an **NMDA receptor antagonist**, is often added for moderate to severe stages to reduce excitotoxicity. - Memantine helps by **modulating glutamate activity**, which is often dysregulated in Alzheimer's disease, thereby potentially improving cognitive function and behavioral symptoms or at least slowing decline. *Ginkgo biloba* - **Ginkgo biloba** is an herbal supplement sometimes touted for cognitive enhancement, but its efficacy in treating or slowing the progression of Alzheimer's disease is **not well-supported by robust clinical evidence**. - It is **not a pharmacologically proven treatment** for established Alzheimer's dementia and would not be considered the most appropriate intervention for a patient with progressive decline already on a standard medication. *Risperidone* - **Risperidone** is an **antipsychotic medication** used to manage severe behavioral symptoms in dementia, such as psychosis, agitation, or severe aggression. - While agitation might be present in dementia, the primary issue described is cognitive decline, and there's no mention of severe behavioral disturbances that would warrant the use of an antipsychotic, which carries significant **side effects** in elderly patients. *Citalopram* - **Citalopram** is a **selective serotonin reuptake inhibitor (SSRI)** primarily used to treat depression and anxiety. - Although depression can coexist with Alzheimer's disease, the patient's symptoms are focused on cognitive decline and memory deficits, with no specific mention of depressive symptoms that would indicate citalopram as the most appropriate treatment for his current presentation. *Vitamin E* - **Vitamin E (alpha-tocopherol)** is an antioxidant that has been investigated for its potential neuroprotective effects in Alzheimer's disease. - While high doses of vitamin E *might* offer a small benefit in slowing functional decline in some patients, its effect is **modest at best**, and it is not considered as effective or as primary a pharmacological intervention as memantine for moderate to severe Alzheimer's.

Question 194: A 45-year-old woman comes to the physician for the evaluation of persistent headaches for the last 2 months. The symptoms started insidiously. Menses had previously occurred at regular 28-day intervals with moderate flow. Her last menstrual period was 12 weeks ago. She is sexually active with her husband but reports decreased interest in sexual intercourse over the past few months. The patient does not smoke or drink alcohol. She is 168 cm (5 ft 6 in) tall and weighs 68 kg (150 lb); BMI is 24 kg/m2. She appears uncomfortable. Vital signs are within normal limits. A urine pregnancy test is negative. A pelvic ultrasound shows atrophic endometrium. A cranial MRI with contrast shows a 2-cm intrasellar mass. A hormone assay is performed and is positive. Which of the following is the most appropriate next step in the management?

A. Temozolomide therapy
B. Observation and outpatient follow-up
C. Cabergoline therapy (Correct Answer)
D. Radiotherapy
E. Biopsy of intrasellar mass

Explanation: ***Cabergoline therapy*** - The patient's symptoms (amenorrhea, decreased libido, headaches) and imaging findings (intrasellar mass) are highly suggestive of a **prolactinoma**. A positive hormone assay further strengthens this diagnosis. - **Cabergoline** is a dopamine agonist and the first-line treatment for prolactinomas, effectively reducing prolactin levels and tumor size in most cases. *Temozolomide therapy* - **Temozolomide** is an oral alkylating agent used primarily for certain aggressive brain tumors like glioblastoma, or for recurrent/refractory pituitary adenomas that are not prolactinomas or have failed other treatments. - It is not the initial treatment of choice for a newly diagnosed prolactinoma, which typically responds well to dopamine agonists. *Observation and outpatient follow-up* - Given the presence of symptomatic features (headaches, amenorrhea, decreased libido) and a 2-cm intrasellar mass, active management to reduce tumor size and prolactin levels is warranted. - **Observation** is usually reserved for asymptomatic, small microprolactinomas (<10 mm) or those with minimal symptoms. *Radiotherapy* - **Radiotherapy** is generally reserved for prolactinomas that are resistant to medical therapy (dopamine agonists) or after surgical failure, and when conventional treatments have failed to control tumor growth or hormone secretion. - It carries risks of side effects like hypopituitarism and optic nerve damage, making it unsuitable as a first-line treatment. *Biopsy of intrasellar mass* - A definitive diagnosis of prolactinoma can often be made based on elevated **prolactin levels** and characteristic imaging findings (intrasellar mass), making biopsy unnecessary in most cases. - Pituitary biopsies are associated with morbidity and are typically reserved for atypical presentations or suspicion of malignancy.

Question 195: A 27-year-old woman comes to the physician for the evaluation of infertility. She has been unable to conceive for the past 2 years. Menses occur at 45 to 80-day intervals. She is 168 cm (5 ft 6 in) tall and weighs 77 kg (170 lb); BMI is 27.4 kg/m2. Physical examination shows facial acne and pigmented hair on the upper lip. Serum studies show elevated levels of testosterone and an LH:FSH ratio of 4:1. Treatment with the appropriate drug for this patient's infertility is begun. Which of the following is the primary mechanism of action of this drug?

A. Activation of pituitary dopamine receptors
B. Activation of granulosa cell aromatase
C. Activation of ovarian luteinizing hormone receptors
D. Inhibition of hypothalamic estrogen receptors (Correct Answer)
E. Inhibition of endometrial progesterone receptors

Explanation: ***Inhibition of hypothalamic estrogen receptors*** - The patient presents with classic symptoms of **polycystic ovarian syndrome (PCOS)**, including **oligomenorrhea** (menses every 45-80 days), **hirsutism**, **acne**, **elevated BMI**, **elevated testosterone**, and an **elevated LH:FSH ratio (4:1)**. - **Clomiphene citrate** is the first-line drug for ovulation induction in PCOS patients with infertility. - Clomiphene is a **selective estrogen receptor modulator (SERM)** that acts as a **competitive antagonist at estrogen receptors in the hypothalamus**. - By blocking estrogen receptors, clomiphene prevents normal **negative feedback inhibition** of GnRH release. - This results in increased **GnRH pulsatility**, leading to increased **FSH and LH secretion** from the anterior pituitary, which promotes **follicular development and ovulation**. *Activation of pituitary dopamine receptors* - This mechanism is characteristic of **dopamine agonists** (e.g., **bromocriptine**, **cabergoline**), which are used to treat infertility due to **hyperprolactinemia**. - These agents activate D2 receptors in lactotroph cells, inhibiting prolactin secretion. - The patient shows no signs of hyperprolactinemia (e.g., galactorrhea, amenorrhea from elevated prolactin). *Activation of granulosa cell aromatase* - Aromatase converts androgens to estrogens in granulosa cells. - While aromatase activity is important in follicular development, **activating aromatase is not a mechanism of any standard ovulation-inducing drug**. - In PCOS, there is often relative aromatase insufficiency, but drugs do not directly activate this enzyme for fertility treatment. *Activation of ovarian luteinizing hormone receptors* - While **exogenous LH or hCG** (which acts on LH receptors) may be used in assisted reproductive technology, this is not the mechanism of **first-line ovulation induction** in PCOS. - Clomiphene works by increasing endogenous LH/FSH release, not by directly activating ovarian receptors. *Inhibition of endometrial progesterone receptors* - This is the mechanism of **mifepristone** (RU-486), an antiprogestin used for medical abortion and occasionally for **endometriosis** or **uterine fibroids**. - Inhibiting progesterone receptors would **prevent implantation** or disrupt pregnancy, which is opposite to the goal of fertility treatment.

Question 196: A 64-year-old man is brought to the emergency department by his wife with a 2-hour history of diarrhea and vomiting. He says that he felt fine in the morning, but noticed that he was salivating, sweating, and feeling nauseated on the way home from his work as a landscaper. The diarrhea and vomiting then started about 10 minutes after he got home. His past medical history is significant for depression and drug abuse. His wife says that he has also been more confused lately and is afraid he may have ingested something unusual. Physical exam reveals miosis, rhinorrhea, wheezing, and tongue fasciculations. Which of the following treatments would most likely be effective for this patient?

A. Sodium bicarbonate
B. Naloxone
C. Atropine (Correct Answer)
D. Fomepizole
E. Ammonium chloride

Explanation: ***Atropine*** - This patient displays classic signs of **organophosphate poisoning**, characterized by **cholinergic crisis** (salivation, sweating, nausea, vomiting, diarrhea, miosis, rhinorrhea, wheezing, fasciculations). **Atropine** is a competitive antagonist of acetylcholine at muscarinic receptors and is the primary antidote, reversing most of these symptoms. - The patient's profession as a **landscaper** increases his exposure risk, and the acute onset of symptoms supports a toxic exposure rather than an infection. *Sodium bicarbonate* - **Sodium bicarbonate** is primarily used to treat **metabolic acidosis**, such as in aspirin overdose or tricyclic antidepressant poisoning, or to alkalinize urine in certain toxic exposures. - While metabolic acidosis can occur in severe organophosphate poisoning, it is not the primary treatment for the **cholinergic symptoms** themselves. *Naloxone* - **Naloxone** is an opioid antagonist used to reverse the effects of **opioid overdose**, characterized by respiratory depression, miosis, and central nervous system depression. - The patient's symptoms of excessive secretions, gastrointestinal distress, and muscle fasciculations are inconsistent with opioid overdose. *Fomepizole* - **Fomepizole** is an alcohol dehydrogenase inhibitor used to treat **methanol and ethylene glycol poisoning**. - These poisonings present with severe metabolic acidosis, visual disturbances (methanol), or renal failure (ethylene glycol), which are not the primary features described in this patient. *Ammonium chloride* - **Ammonium chloride** is an acidifying agent used to treat severe **metabolic alkalosis** or to increase the excretion of basic drugs. - It is not indicated for the treatment of organophosphate poisoning and would likely exacerbate any existing acidosis.

Question 197: A 65-year-old male who is being treated for depression visits your emergency room complaining of being unable to urinate. In addition, the patient complains of tachycardia and dry mouth. He has no history of benign prostatic hyperplasia and reports of only being on one psychiatric medication. What type of psychiatric medication would cause such a side effect profile?

A. Tricyclic antidepressant (Correct Answer)
B. Serotonin norepinephrine reuptake inhibitor
C. Monoamine oxidase inhibitor
D. Selective serotonin reuptake inhibitor
E. Aminoketone

Explanation: ***Tricyclic antidepressant*** - The patient's symptoms of **urinary retention**, dry mouth, and tachycardia are characteristic **anticholinergic side effects**, frequently seen with TCAs. - TCAs block muscarinic acetylcholine receptors, leading to these peripheral effects. *Serotonin norepinephrine reuptake inhibitor* - SNRIs primarily affect serotonin and norepinephrine reuptake and are less likely to cause severe anticholinergic effects like urinary retention. - While they can cause some dry mouth or tachycardia due to noradrenergic effects, the combination with significant urinary retention points away from SNRIs. *Monoamine oxidase inhibitor* - MAOIs are generally associated with side effects such as **hypertensive crisis** (with tyramine-rich foods), orthostatic hypotension, and insomnia. - They do not typically cause the prominent anticholinergic syndrome described. *Selective serotonin reuptake inhibitor* - SSRIs primarily affect serotonin reuptake and are known for side effects such as **gastrointestinal upset**, sexual dysfunction, and anxiety. - They have a low affinity for muscarinic receptors and are less likely to cause significant anticholinergic effects like urinary retention. *Aminoketone* - Aminoketones (e.g., bupropion) typically act by inhibiting the reuptake of dopamine and norepinephrine. - Common side effects include **insomnia**, agitation, and **seizure risk** at high doses; they do not typically produce the anticholinergic profile seen here.

Question 198: A 69-year-old man comes to the physician because of a 3-month history of urinary urgency, nocturia, and progressive pain in his lower back. The pain is worse at night and does not respond to ibuprofen. Rectal examination shows an enlarged, asymmetric prostate with a nodular surface. Prostate-specific antigen concentration is 11 ng/ml (N < 4). A biopsy of the prostate shows a high-grade adenocarcinoma. A CT scan of the pelvis shows multiple osteoblastic lesions of the lumbar spine. The patient is started on a drug that competes with androgens for interaction with the testosterone receptors. Treatment with which of the following drugs was most likely initiated in this patient?

A. Docetaxel
B. Flutamide (Correct Answer)
C. Finasteride
D. Degarelix
E. Leuprolide

Explanation: ***Flutamide*** - The patient has **metastatic prostate cancer** with osteoblastic lesions, indicating a need for **androgen-deprivation therapy**. Flutamide is an **androgen receptor antagonist** that competes with androgens for binding to testosterone receptors. - It is often used in combination with **GnRH agonists** (like leuprolide) to prevent **tumor flare** caused by the initial surge in testosterone, or as monotherapy in some cases. *Docetaxel* - **Docetaxel** is a **chemotherapeutic agent** (a taxane) used primarily for patients with **castration-resistant prostate cancer** or when hormonal therapies are no longer effective. - It works by stabilizing microtubules, preventing cell division, and does not compete with androgens for testosterone receptors. *Finasteride* - **Finasteride** is a **5-alpha reductase inhibitor** that blocks the conversion of testosterone to **dihydrotestosterone (DHT)**, which is the more potent androgen in the prostate. - It is used for **benign prostatic hyperplasia (BPH)** and **androgenic alopecia**, but not typically for metastatic prostate cancer as the primary treatment mechanism described. *Degarelix* - **Degarelix** is a **GnRH receptor antagonist** that directly suppresses the release of LH and FSH, leading to a rapid and sustained reduction in testosterone levels without an initial flare. - While it causes androgen deprivation, it does not directly compete with androgens for binding to the testosterone receptors on cancer cells; its action is upstream. *Leuprolide* - **Leuprolide** is a **GnRH agonist** that initially causes a surge in LH and FSH, followed by downregulation and desensitization of the GnRH receptors, leading to reduced testosterone production. - Like degarelix, it causes androgen deprivation, but it does not directly compete with androgens at the receptor level; its action is also upstream.

Question 199: A 16-year-old boy presents with shortness of breath after prolonged exposure to cold air during a recent hike with his friends. Past medical history is significant for asthma, untreated because he doesn't like using medications. The patient says he is a non-smoker and occasionally drinks alcohol. On physical examination, his temperature is 37.0°C (98.6°F), pulse rate is 120/min, blood pressure is 114/76 mm Hg, and respiratory rate is 32/min. Auscultation of the chest reveals bilateral wheezing. Nebulized ipratropium bromide results in significant clinical improvement. Which of the following second messenger systems is affected by this drug?

A. Tyrosine kinase system
B. Phosphoinositol system (Correct Answer)
C. Arachidonic acid system
D. Cyclic guanosine monophosphate (cGMP) system
E. Cyclic adenosine monophosphate (cAMP) system

Explanation: ***Phosphoinositol system*** - **Ipratropium bromide** is an **anticholinergic drug** that blocks **muscarinic M3 receptors** on bronchial smooth muscle. - M3 receptors are **Gq protein-coupled receptors** that activate the **phosphoinositol (PIP2) pathway**. - When activated, Gq proteins stimulate **phospholipase C (PLC)**, which cleaves **PIP2** into **IP3** (inositol trisphosphate) and **DAG** (diacylglycerol). - IP3 increases **intracellular calcium**, causing **bronchoconstriction**; ipratropium **blocks this pathway**, resulting in **bronchodilation**. - This is the primary second messenger system affected by ipratropium. *Cyclic adenosine monophosphate (cAMP) system* - The **cAMP system** is associated with **β2-adrenergic receptors** (Gs-coupled), not muscarinic M3 receptors. - **Beta-agonists** like albuterol work through cAMP to cause bronchodilation, but ipratropium does not directly affect this pathway. - While there may be indirect effects, M3 receptors primarily signal through the phosphoinositol system, not cAMP. *Tyrosine kinase system* - The **tyrosine kinase system** is activated by **growth factors** (e.g., insulin, EGF, PDGF) through receptor tyrosine kinases. - This pathway involves autophosphorylation and activation of downstream signaling cascades like **MAPK** and **PI3K/Akt**. - Muscarinic receptors are **G protein-coupled receptors (GPCRs)**, not tyrosine kinase receptors. *Arachidonic acid system* - The **arachidonic acid pathway** produces **prostaglandins, leukotrienes**, and **thromboxanes** via **cyclooxygenase** and **lipoxygenase** enzymes. - This system is targeted by **NSAIDs** (block COX) and **leukotriene modifiers** (e.g., montelukast), not by anticholinergics. - While inflammation plays a role in asthma, ipratropium's mechanism does not primarily involve this pathway. *Cyclic guanosine monophosphate (cGMP) system* - The **cGMP system** is primarily associated with **nitric oxide (NO) signaling** and **atrial natriuretic peptide (ANP)**. - NO activates **guanylyl cyclase**, increasing cGMP levels and causing **smooth muscle relaxation** and **vasodilation**. - M3 muscarinic receptors do not primarily signal through the cGMP pathway.

Question 200: A 23-year-old man presents to the physician with nausea, vomiting, constipation, and abdominal pain for the past 24 hours. He has also developed difficulty in swallowing and blurring of vision. He also complains of significant dryness of his mouth and throat. When asked about his diet, he reports that he has been saving money by eating dented and old canned goods. On physical examination, his vital signs are stable. His neurologic examination reveals bilateral fixed dilated pupils, weakness of extraocular muscles, and weak gag reflex, while sensations and gait are normal. Laboratory evaluation of his stool isolates a toxin produced by gram-positive, anaerobic, spore-forming bacilli. Which of the following mechanisms best explains the action of the toxin?

A. Prolonged depolarization of NM receptors
B. Blockade of release of acetylcholine at neuromuscular junctions (Correct Answer)
C. Competitive antagonism of acetylcholine at postsynaptic receptors
D. Blockade of voltage-gated fast sodium channels in motor neurons
E. Inactivation of acetylcholinesterase at neuromuscular junctions

Explanation: ***Blockade of release of acetylcholine at neuromuscular junctions*** - The clinical presentation, including the consumption of **dented canned goods**, **fixed dilated pupils**, **extraocular muscle weakness**, and **weak gag reflex**, is classic for **botulism**. - The botulinum toxin, produced by *Clostridium botulinum*, acts by **preventing the release of acetylcholine** from presynaptic terminals at neuromuscular junctions, leading to **flaccid paralysis**. *Prolonged depolarization of NM receptors* - This mechanism is associated with **depolarizing neuromuscular blockers** (e.g., succinylcholine) which initially cause fasciculations followed by paralysis due to persistent receptor activation, not seen in botulism. - Such agents lead to initial muscle contraction before paralysis, unlike the direct weakness caused by botulinum toxin. *Competitive antagonism of acetylcholine at postsynaptic receptors* - This mechanism is characteristic of **nondepolarizing neuromuscular blockers** (e.g., rocuronium), which compete with acetylcholine for binding sites on the postsynaptic membrane. - While this also causes muscle weakness, it is not the action of botulinum toxin, which acts presynaptically. *Blockade of voltage-gated fast sodium channels in motor neurons* - Toxins that block **voltage-gated sodium channels** (e.g., tetrodotoxin, saxitoxin) prevent nerve impulse generation, leading to paralysis by inhibiting action potential propagation. - This mechanism would affect nerve conduction upstream of neurotransmitter release, which is distinct from botulinum toxin's action. *Inactivation of acetylcholinesterase at neuromuscular junctions* - Inactivation of **acetylcholinesterase** (e.g., by organophosphates) leads to an accumulation of acetylcholine in the synaptic cleft, causing **cholinergic crisis** with symptoms like excessive salivation, lacrimation, urination, and defecation, which are the opposite of the dry mouth and constipation seen here. - This mechanism would cause overstimulation rather than paralysis from neurotransmitter deficiency at the synapse.

Question 201: A 65-year-old woman returns to the outpatient oncology clinic to follow up on her recently diagnosed breast cancer. A few months ago, she noticed a lump during a breast self-exam that was shown to be breast cancer. A lumpectomy revealed invasive ductal carcinoma that was estrogen- and progesterone receptor-positive with nodal metastases. She is following up to discuss treatment options. She had her last menstrual period 10 years ago and has not had any spotting since that time. Her mother had breast cancer and she remembered her taking chemotherapy and had a poor quality of life, thus she asks not to be treated similarly. Which of the following is the mechanism of action of the best treatment option for this patient?

A. Cell cycle arrest
B. Estrogen receptors downregulation in the breast
C. Inhibit peripheral conversion of androgens to estrogen (Correct Answer)
D. Antagonist for estrogen receptors in the breast
E. Antagonist for estrogen receptors in the hypothalamus

Explanation: ***Inhibit peripheral conversion of androgens to estrogen*** - The patient has **estrogen and progesterone receptor-positive breast cancer** and is **postmenopausal**. Aromatase inhibitors (e.g., anastrozole, letrozole, exemestane) are the best treatment option for postmenopausal women with hormone-sensitive breast cancer. - Aromatase inhibitors work by blocking the **aromatase enzyme**, which is responsible for the peripheral conversion of androgens to estrogens, thereby reducing estrogen levels in postmenopausal women and inhibiting cancer growth. *Cell cycle arrest* - While many chemotherapeutic agents induce cell cycle arrest, this patient's preference for avoiding chemotherapy and the **hormone-sensitive nature of her cancer** suggest a less aggressive, targeted hormonal therapy is more appropriate. - Cell cycle arrest is a general mechanism for many cancer treatments, but it's not the primary, specific mechanism for the best treatment for this particular patient given her clinicopathological features and preferences. *Estrogen receptors downregulation in the breast* - This mechanism is characteristic of **selective estrogen receptor degraders (SERDs)** like fluvestrant, which destroy estrogen receptors. - While an effective treatment for hormone-sensitive breast cancer, especially in later lines, aromatase inhibitors are generally preferred as initial adjuvant therapy in postmenopausal women with positive nodal disease. *Antagonist for estrogen receptors in the breast* - This describes the mechanism of **selective estrogen receptor modulators (SERMs)** such as tamoxifen, which act as antagonists in breast tissue and agonists in other tissues like bone. - Tamoxifen is primarily used in premenopausal women or in high-risk postmenopausal women who cannot tolerate aromatase inhibitors or for other specific indications; aromatase inhibitors are generally preferred for postmenopausal women with nodal involvement. *Antagonist for estrogen receptors in the hypothalamus* - Antagonism of estrogen receptors in the hypothalamus could theoretically impact the **hypothalamic-pituitary-gonadal axis**, but this is not the direct or primary therapeutic mechanism for treating hormone-sensitive breast cancer. - Drugs like **clomiphene citrate**, which induce ovulation, act at the hypothalamus but are not used for breast cancer treatment.

Question 202: A 30-year-old man presents to his primary care doctor for a 2 month follow-up appointment. He had recently separated from his male partner of 10 years and has been struggling to maintain his weight and the rigors of work in a new start-up company. At his initial visit, he was prescribed escitalopram. 2 weeks later, the patient was instructed to continue taking the medication despite feeling more depressed. After expressing increased desire to carry out suicidal thoughts, he was hospitalized for a brief course. During this visit, he reports that he is feeling much better, but he has an elective inguinal hernia repair scheduled for the end of the week. "The surgeon said to not take anything before the surgery. Besides, I'm feeling better and don't feel like taking escitalopram everyday." What is the most appropriate response?

A. Continue escitalopram on day of surgery and continue afterwards for 4 more months (Correct Answer)
B. Hold escitalopram the day of surgery and continue afterwards for 4 more months
C. Continue escitalopram until surgery and discontinue afterwards
D. Discontinue escitalopram
E. Hold escitalopram the day before surgery and continue afterwards for 4 more months

Explanation: ***Continue escitalopram on day of surgery and continue afterwards for 4 more months*** - For patients on **antidepressants** prior to surgery, it is generally recommended to continue the medication throughout the perioperative period to avoid **withdrawal symptoms** and potential relapse of depressive symptoms. - Continuing escitalopram for at least **4-9 months** after symptom resolution is recommended to reduce the risk of relapse for a first episode of depression. *Hold escitalopram the day of surgery and continue afterwards for 4 more months* - Holding escitalopram on the day of surgery increases the risk of **serotonin withdrawal syndrome**, which can manifest as dizziness, nausea, headaches, and flu-like symptoms. - There is generally **no medical reason** to discontinue SSRIs like escitalopram perioperatively as they do not significantly increase the risk of bleeding or anesthesia complications. *Continue escitalopram until surgery and discontinue afterwards* - Discontinuing escitalopram immediately after surgery, especially given the patient's recent hospitalization for suicidal ideation, poses a high risk of **relapse of depression** and potential re-emergence of suicidal thoughts. - The patient's statement "feeling better" should be interpreted cautiously; it might reflect a **partial response** to treatment rather than full remission, and abrupt discontinuation can destabilize his mental health. *Discontinue escitalopram* - Abrupt discontinuation of escitalopram, particularly given the patient's past history of **severe depression** and recent suicidal ideation, is highly inadvisable and significantly increases the risk of **relapse** and withdrawal symptoms. - This approach fails to address the underlying depression and the need for continued treatment to maintain mental stability. *Hold escitalopram the day before surgery and continue afterwards for 4 more months* - Similar to holding on the day of surgery, holding escitalopram the day before can initiate **withdrawal symptoms** and destabilize the patient's mood, potentially complicating the perioperative period. - There is no clinical indication for a pre-operative hold of escitalopram, as its continuation is generally considered safe and beneficial.

Question 203: A medical examiner was called to investigate the death of a 75-year-old type 1 diabetic Caucasian male who was a retired physician. His caretaker discovered his body in the bedroom with an empty syringe and a small bottle of lispro lying on the nightstand. She explains that his wife of 50 years passed away six months ago and that he had no children or family. He had become extremely depressed and did not want to live anymore. Which of the following would be most consistent with his blood chemistry if a blood sample were taken?

A. Glucose: 95 mg/dL, high insulin and C-peptide levels
B. Glucose: 25 mg/dL, high insulin and absent C-peptide levels (Correct Answer)
C. Glucose: 95 mg/dL, low insulin and low C-peptide levels
D. Glucose: 25 mg/dL, high insulin and high C-peptide levels
E. Glucose: 25 mg/dL, high insulin and normal C-peptide levels

Explanation: **Glucose: 25 mg/dL, high insulin and absent C-peptide levels** - The presence of an empty syringe and a bottle of **lispro**, a **rapid-acting insulin**, indicates a likely insulin overdose. This would lead to profound **hypoglycemia** (glucose: 25 mg/dL) and **high insulin levels**. - As the patient has **Type 1 diabetes**, his pancreas does not produce insulin, resulting in **absent C-peptide levels**. Administered exogenous insulin (lispro) does not contain C-peptide, so C-peptide levels would remain absent even with high exogenous insulin. *Glucose: 95 mg/dL, high insulin and C-peptide levels* - A glucose level of 95 mg/dL is within the normal range and inconsistent with a fatal insulin overdose scenario, which typically causes severe **hypoglycemia**. - High insulin with high C-peptide levels would typically suggest conditions like an **insulinoma** or an overdose of a sulfonylurea, which stimulates endogenous insulin production, not an overdose of exogenous insulin in a Type 1 diabetic. *Glucose: 95 mg/dL, low insulin and low C-peptide levels* - Glucose at 95 mg/dL is normal to low-normal, which would not typically be seen in a fatal insulin overdose. - Low insulin and low C-peptide levels are characteristic of controlled or untreated **Type 1 diabetes** or other forms of insulin deficiency, not an acute insulin overdose. *Glucose: 25 mg/dL, high insulin and high C-peptide levels* - While a glucose level of 25 mg/dL and high insulin are consistent with an insulin overdose, **high C-peptide levels** in a Type 1 diabetic are contradictory. Type 1 diabetics produce little to no C-peptide. - High C-peptide levels would suggest endogenous insulin production, which is absent in Type 1 diabetes and not introduced by exogenous lispro. *Glucose: 25 mg/dL, high insulin and normal C-peptide levels* - Although **hypoglycemia** and **high insulin** are consistent with an overdose, "normal" C-peptide levels are unlikely in a Type 1 diabetic who has received exogenous insulin. - In Type 1 diabetes, C-peptide is typically very low or undetectable, reflecting minimal to no endogenous insulin production.

Question 204: A 53-year-old woman with type 2 diabetes mellitus is admitted for evaluation of recurrent episodes of nausea, tremors, and excessive sweating. She works as a nurse and reports self-measured blood glucose levels below 50 mg/dL on several occasions. Her family history is positive for borderline personality disorder. The only medication listed in her history is metformin. Which of the following is the most appropriate next step in management?

A. Measure serum C-peptide concentration
B. Ask the patient if she is taking any medications other than metformin (Correct Answer)
C. Search the patient's belongings for insulin
D. Measure glycated hemoglobin concentration
E. Report the patient to her employer

Explanation: ***Ask the patient if she is taking any medications other than metformin*** - The patient's presentation with recurrent **hypoglycemic symptoms** (nausea, tremors, sweating) and documented low blood glucose, while only being prescribed metformin (which does not cause hypoglycemia), strongly suggests **exogenous insulin or sulfonylurea use**. - A direct question about other medications is a crucial initial step to ascertain the cause of her hypoglycemia and to rule out **factitious hypoglycemia**, especially given her profession as a nurse and a family history that might suggest psychological vulnerabilities, although not a direct diagnosis for the patient. *Measure serum C-peptide concentration* - While **low C-peptide** in the presence of hypoglycemia would suggest exogenous insulin administration, and high C-peptide might point to an insulinoma, this test should be done *after* ruling out common causes like the undisclosed use of other medications. - This is a more invasive and less direct initial step compared to simply asking the patient about medication use, especially when a readily reversible cause (undisclosed medication) is possible. *Search the patient's belongings for insulin* - Searching a patient's belongings without their consent is a serious ethical breach and a violation of privacy. - This action should only be considered as a last resort in extreme circumstances and with appropriate legal and ethical oversight, not as an initial diagnostic step. *Measure glycated hemoglobin concentration* - **Glycated hemoglobin (HbA1c)** reflects average blood glucose levels over the past 2-3 months and is used to monitor long-term glycemic control in diabetic patients. - While useful for diabetes management, it will not directly identify the acute cause of recurrent hypoglycemic episodes or distinguish between endogenous and exogenous insulin sources. *Report the patient to her employer* - Reporting the patient to her employer prematurely, without a definitive diagnosis or understanding the full context of her condition, is unethical and unprofessional. - The immediate priority is to diagnose and manage the patient's medical condition, ensuring her safety and well-being, before considering professional implications.

Question 205: A 22-year-old man presents to the emergency department with a 2-day history of fever and altered mentation. He reports fever without chills and rigors and denies sore throat, abdominal pain, headache, loose stool, burning micturition, or seizures. He has a history of tics and is currently on a low dose of haloperidol. At the hospital, his temperature is 39.6°C (103.2°F); the blood pressure is 126/66 mm Hg, and the pulse is 116/min. He is profusely sweating and generalized rigidity is present. He is confused and disoriented. He is able to move all his limbs. Normal deep tendon reflexes are present with bilateral downgoing plantar responses. A brain MRI is unremarkable. Urine toxicology is negative. The white blood cell count is 14,700/mm3. Creatine kinase is 5600 U/L. Lumbar puncture is performed and cerebrospinal fluid (CSF) studies show: CSF opening pressure 22 cm H20 CSF white blood cells 4 cells/mm3 CSF red blood cells 0 cells/mm3 CSF glucose 64 mg/dL CSF protein 48 mg/dL Serum glucose 96 mg/dL What is the most likely diagnosis?

A. Cerebral venous sinus thrombosis
B. Acute disseminated encephalomyelitis
C. Encephalitis
D. Neuroleptic malignant syndrome (Correct Answer)
E. Meningitis

Explanation: ***Neuroleptic malignant syndrome*** - The patient's presentation with **fever, altered mentation, muscle rigidity, profuse sweating, elevated creatine kinase**, and a history of **haloperidol** use is highly consistent with Neuroleptic Malignant Syndrome (NMS). - **Haloperidol** is a dopamine antagonist, and its use is a well-known risk factor for NMS, which is characterized by a severe idiosyncratic reaction to neuroleptic medications. *Cerebral venous sinus thrombosis* - This condition typically presents with **severe headaches, focal neurological deficits, and seizures**, often seen on MRI or CT venography. - The patient's normal MRI and generalized symptoms without focal deficits make this diagnosis less likely. *Acute disseminated encephalomyelitis* - ADEM is an **autoimmune demyelinating disease** often following an infection or vaccination, typically presenting with multifocal neurological deficits. - The patient's presentation, particularly the muscle rigidity and elevated CK, is not typical for ADEM, and the MRI is unremarkable. *Encephalitis* - Encephalitis involves **brain inflammation**, manifesting as fever, altered mental status, and seizures, with CSF usually showing **lymphocytic pleocytosis**. - The CSF in this patient is largely normal (minimal pleocytosis), and the prominent **muscle rigidity and very high CK** point away from uncomplicated encephalitis. *Meningitis* - Meningitis primarily involves **inflammation of the meninges**, characterized by fever, headache, nuchal rigidity, and photophobia, with CSF showing pleocytosis and abnormal protein/glucose. - While the patient has fever and altered mentation, **nuchal rigidity is absent**, and the CSF findings (especially the normal cell count and glucose) do not support a diagnosis of meningitis.

Question 206: A 64-year-old man presents to his primary care physician because of a tremor that he has developed over the last several months. He says that the tremor is worst when he is resting but becomes better when he engages in movements such as picking up the remote for his TV. His wife also says that his movements have become slower over the last few months. Physical exam reveals increased resistance to passive motion of his extremities. Gait exam also shows trouble with starting movement and short, shuffling steps. The most likely cause of this patient's symptoms involve the degeneration of a certain subset of neurons. When the substance released by these neurons interact with a G-alpha-s coupled receptor, which of the following effects occurs?

A. Stimulation of the subthalamic nucleus
B. Inhibition of the globus pallidus internus (Correct Answer)
C. Inhibition of the globus pallidus externus
D. Stimulation of the globus pallidus externus
E. Stimulation of the globus pallidus internus

Explanation: ***Inhibition of the globus pallidus internus*** - This patient's symptoms are highly suggestive of **Parkinson's disease**, characterized by **resting tremor**, **bradykinesia** (slow movements), **rigidity** (increased resistance to passive motion), and **gait abnormalities**. - Parkinson's disease results from the degeneration of **dopaminergic neurons** in the **substantia nigra pars compacta**. Dopamine released by these neurons acts on **D1 receptors (Gαs-coupled)** in the striatum, which are part of the **direct pathway** of the basal ganglia. - D1 receptor activation **excites striatal neurons** in the direct pathway, which then send **GABAergic (inhibitory) projections** to the **globus pallidus internus (GPi)**, resulting in **inhibition of the GPi** and ultimately **facilitating movement**. *Stimulation of the subthalamic nucleus* - The subthalamic nucleus (STN) is **stimulated by the indirect pathway**, which is relatively overactive in Parkinson's disease due to dopamine deficiency. - Stimulation of the STN leads to **increased excitation of the GPi**, thus suppressing movement. - D1 (Gαs-coupled) receptors do **not** directly stimulate the STN; they act on the direct pathway through the striatum. *Inhibition of the globus pallidus externus* - In the indirect pathway, dopamine acts through **D2 (Gαi-coupled) receptors**, not D1 (Gαs-coupled) receptors. - D2 activation **inhibits striatal neurons** in the indirect pathway, reducing their inhibitory output to the **globus pallidus externus (GPe)**, which leads to disinhibition of the GPe. - This is **not** the effect of D1 (Gαs-coupled) receptor activation. *Stimulation of the globus pallidus externus* - The **GPe is not stimulated by D1 receptor activation**. - D1 receptors act primarily on the **direct pathway** (striatum → GPi), not the indirect pathway involving the GPe. - The GPe is influenced by D2 receptor activity in the indirect pathway, not D1 receptors. *Stimulation of the globus pallidus internus* - D1 receptor activation in the direct pathway leads to **inhibition, not stimulation**, of the GPi. - The GPi is **excited by the subthalamic nucleus** in the indirect pathway, but this is not mediated by D1 (Gαs-coupled) receptors. - **Inhibition of the GPi** (via excited striatal neurons) is the correct effect of D1 receptor activation, facilitating movement.

Question 207: A 28-year-old female is brought to the emergency department after being found unconscious outside of a local night club by her friends. On arrival the patient is stuporous. Her temperature is 35°C (95°F), blood pressure is 105/75 mm Hg, pulse is 55/min, and respirations are 10/min. Examination shows dry mucous membranes. The pupils are small and react sluggishly to light. She does not respond to any commands, and painful stimuli cause her to withdraw all extremities. No injection marks can be found on her extremities. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of her symptoms?

A. Heroin (Correct Answer)
B. Cannabis
C. Phencyclidine
D. MDMA
E. Amitriptyline

Explanation: ***Heroin*** - The patient's **depressed mental status** (**stupor**, **unconscious**), **miotic (small) pupils**, **bradycardia**, **bradypnea**, and **hypothermia** are all classic signs of **opioid overdose**. - Although no injection marks were found, heroin can be **snorted** or **smoked**, and the combination of symptoms strongly points towards opioid toxicity. - The **dry mucous membranes** are somewhat atypical for pure opioid toxicity (more consistent with anticholinergic effects) but may be secondary to **dehydration** or environmental exposure; the overwhelming clinical presentation of **opioid toxidrome** (miosis, respiratory depression, CNS depression) takes precedence. *Cannabis* - While cannabis can cause **somnolence** and **impaired coordination**, it typically does not lead to severe **respiratory depression**, **pinpoint pupils**, or **unconsciousness** to this degree. - The vital signs are not consistent with typical cannabis intoxication, which might include **tachycardia** and **conjunctival injection**. *Phencyclidine* - **Phencyclidine (PCP)** intoxication is usually characterized by **agitation**, **hallucinations**, **nystagmus**, and sometimes **hypertension** and **tachycardia**, which contradict this patient's presentation. - While it can cause altered mental status, the **miosis**, **bradycardia**, and **respiratory depression** are not typical. *MDMA* - **MDMA (Ecstasy)** typically causes **sympathomimetic effects** such as **tachycardia**, **hypertension**, **hyperthermia**, **mydriasis (dilated pupils)**, and **agitation**, which are all opposite to the patient's symptoms. - It does not induce significant **respiratory depression** or **miosis**. *Amitriptyline* - **Amitriptyline**, a tricyclic antidepressant (TCA), overdose can cause significant central nervous system depression, but it is typically associated with **anticholinergic effects** such as **mydriasis (dilated pupils)**, **tachycardia**, **dry mucous membranes**, **urinary retention**, and potentially **seizures** or **arrhythmias**. - The **pinpoint pupils** and **bradycardia** are inconsistent with TCA overdose, making this diagnosis unlikely despite the presence of dry mucous membranes.

Question 208: A 28-year-old woman presents with weight gain and a milky-white discharge from her breasts. Patient says she noticed herself gaining weight and a milky white discharge from her breasts. Past medical history is significant for schizophrenia, recently diagnosed and treated with risperidone. No history of headache, nausea, and vomiting. No other current medications. Her last menstrual period was 2 months ago. Review of systems is significant for decreased libido. Patient is afebrile and vital signs are within normal limits. On physical examination, patient had a weight gain of 3 kg (6.6 lb) over the past month. There is bilateral breast tenderness present. A urine pregnancy test is negative. Which of the following is the most likely etiology of this patient’s symptoms?

A. Increase in dopamine activity in mesolimbic pathway
B. Decrease in dopamine activity in mesolimbic pathway
C. Decrease in dopamine activity in tuberoinfundibular pathway (Correct Answer)
D. Decrease in dopamine activity in nigrostriatal pathway
E. Increase in dopamine activity in tuberoinfundibular pathway

Explanation: ***Decrease in dopamine activity in tuberoinfundibular pathway*** - The patient is taking **risperidone**, an antipsychotic that blocks **dopamine D2 receptors**. This blockade in the **tuberoinfundibular pathway** leads to increased prolactin secretion. - Elevated **prolactin** levels cause **galactorrhea** (milky discharge), **amenorrhea** (missed periods), **weight gain**, and **decreased libido**. *Increase in dopamine activity in mesolimbic pathway* - An **increase in dopamine activity** in the **mesolimbic pathway** is associated with the positive symptoms of **schizophrenia** (e.g., hallucinations, delusions). - Antipsychotics like risperidone aim to decrease this activity, not increase it, and this pathway is not directly involved in prolactin regulation. *Decrease in dopamine activity in mesolimbic pathway* - A **decrease in dopamine activity** in the **mesolimbic pathway** is the desired therapeutic effect of antipsychotics like risperidone, reducing psychotic symptoms. - While it explains the treatment of schizophrenia, it does not explain the specific side effects of hyperprolactinemia. *Decrease in dopamine activity in nigrostriatal pathway* - A **decrease in dopamine activity** in the **nigrostriatal pathway** is responsible for **extrapyramidal symptoms** (EPS) such as parkinsonism (tremor, rigidity), akathisia, and dystonia. - While antipsychotics can cause EPS, these are not the predominant symptoms (galactorrhea, weight gain, amenorrhea) described in the patient. *Increase in dopamine activity in tuberoinfundibular pathway* - An **increase in dopamine activity** in the **tuberoinfundibular pathway** would lead to a decrease in prolactin secretion, as dopamine is a **prolactin-inhibiting hormone**. - This would result in symptoms opposite to what the patient is experiencing, such as no galactorrhea or even hypoprolactinemia.

Question 209: A 26-year-old man is brought to the emergency department by his friends because of blurred vision and slurred speech for the past 6 hours. He had some difficulty swallowing his food during lunch and has weakness in both arms. Two weeks ago, he had an upper respiratory infection that resolved spontaneously. He lives independently and returned from his grandparents' farm 2 days ago. He commonly consumes canned vegetables and fruits. He is alert and oriented to person, place, and time. His temperature is 37°C (98.6°F), pulse is 88/min, respirations are 10/min and labored, and blood pressure is 110/70 mm Hg. Examination shows bilateral nystagmus and ptosis. The pupils are dilated and not reactive to light. Muscle strength of the facial muscles and bilateral upper extremities is decreased. Upper extremity deep tendon reflexes are 1+ bilaterally. Cardiopulmonary examination shows no abnormalities. Which of the following is the most likely cause for this patient's symptoms?

A. Autoantibodies against myelin
B. Chemical that inhibits acetylcholinesterase
C. Autoantibodies against ACh receptors
D. Toxin that inhibits ACh release (Correct Answer)
E. Cell-mediated focal demyelination

Explanation: **Toxin that inhibits ACh release** - The patient's symptoms, including **blurred vision, ptosis, fixed dilated pupils, slurred speech, dysphagia, and descending flaccid paralysis** (weakness in arms before legs, with reduced reflexes), are highly characteristic of **botulism**. - **Clostridium botulinum toxin** inhibits the release of **acetylcholine (ACh)** at the neuromuscular junction and parasympathetic synapses, leading to these symptoms. The history of consuming **canned foods** and returning from a farm suggests a potential exposure source. *Autoantibodies against myelin* - This mechanism describes **Guillain-Barré syndrome (GBS)**, which typically presents with **ascending paralysis** and areflexia, often following an infection. - While GBS can cause some cranial nerve involvement, the prominent **fixed dilated pupils (pupil-sparing paralysis is typical in GBS)** and the **descending pattern of weakness** in this patient are inconsistent with GBS. *Chemical that inhibits acetylcholinesterase* - This mechanism is associated with **organophosphate poisoning**, which presents with a **cholinergic crisis**. - Symptoms include **miosis**, increased salivation, lacrimation, urination, defecation, gastrointestinal upset, emesis (**SLUDGE** syndrome), bradycardia, and muscle fasciculations, none of which are noted in this patient. *Autoantibodies against ACh receptors* - This is the underlying mechanism of **myasthenia gravis**, an autoimmune disorder characterized by **fluctuating muscle weakness** that worsens with activity and improves with rest. - Key features often include **ptosis and diplopia**, but pupils are typically **spared**. The weakness in myasthenia gravis is not typically descending with fixed dilated pupils, and it does not usually present acutely with such severe widespread involvement. *Cell-mediated focal demyelination* - This describes the pathology of **multiple sclerosis (MS)**, a chronic inflammatory demyelinating disease of the central nervous system. - MS typically presents with **diverse neurological symptoms** that can be relapsing-remitting or progressive, often including sensory disturbances, motor weakness, visual changes (e.g., optic neuritis), and bladder dysfunction. It does not typically cause acute, rapidly progressive flaccid paralysis with fixed dilated pupils and bulbar symptoms as seen here.

Question 210: A 17-year-old boy presents to the office with allergic rhinitis. He reports symptoms of sneezing, nasal congestion, itching, and postnasal drainage every September at the start of the school year. He has a family history of childhood asthma and eczema. He has not tried any medications for his allergies. Which of the following medications is the most appropriate next step to manage the patient's symptoms?

A. Intranasal cromolyn sodium
B. Intranasal decongestants
C. Oral antihistamines
D. Intranasal antihistamines
E. Intranasal corticosteroids (Correct Answer)

Explanation: ***Intranasal corticosteroids*** - Are considered **first-line treatment** for persistent allergic rhinitis due to their broad anti-inflammatory effects, effectively reducing sneezing, congestion, itching, and postnasal drip. - They provide **superior symptom control** compared to other medications for moderate-to-severe symptoms, which this patient appears to have based on the regular occurrence and multiple symptoms. *Intranasal cromolyn sodium* - This is a **mast cell stabilizer** that prevents the release of inflammatory mediators, but it is less potent than corticosteroids. - It requires **frequent dosing** (3-4 times daily) and is generally reserved for patients with mild, intermittent symptoms or as an adjunct therapy. *Intranasal decongestants* - Provide temporary relief for **nasal congestion** but do not address other symptoms like sneezing or itching. - Long-term use (more than 3-5 days) can lead to **rhinitis medicamentosa** (rebound congestion), making them unsuitable for chronic seasonal allergies. *Oral antihistamines* - Are effective for sneezing, itching, and rhinorrhea but are generally **less effective for nasal congestion** and postnasal drip compared to intranasal corticosteroids. - Second-generation oral antihistamines (e.g., loratadine, fexofenadine) are preferred over first-generation due to **less sedation**. *Intranasal antihistamines* - Provide rapid relief for sneezing, itching, and rhinorrhea and can be more effective than oral antihistamines for nasal symptoms. - However, they are **less effective for nasal congestion** and postnasal drip compared to intranasal corticosteroids, which address the wider inflammatory response.

Question 211: A 41-year-old woman with subclinical hypothyroidism comes to the physician because of a 6-month history of progressively worsening headaches and irregular menses. Her menses had previously occurred at regular 30-day intervals with moderate flow, but her last menstrual period was 12 weeks ago. She also reports that her interest in sexual intercourse has recently decreased. Her serum prolactin level is elevated. Which of the following is the most appropriate pharmacotherapy for this patient?

A. Methyldopa
B. Estrogen
C. L-thyroxine
D. Bromocriptine (Correct Answer)
E. Metoclopramide

Explanation: ***Bromocriptine*** - The patient's symptoms (headaches, irregular menses, decreased libido) coupled with an **elevated serum prolactin level** are indicative of **hyperprolactinemia**, likely due to a pituitary adenoma (prolactinoma). - **Bromocriptine** is a **dopamine agonist** that effectively reduces prolactin secretion by stimulating dopamine D2 receptors in the pituitary, leading to resolution of symptoms and potential shrinkage of prolactinomas. - This is the **first-line pharmacotherapy** for prolactinomas. *Methyldopa* - **Methyldopa** is an **antihypertensive medication** that works by stimulating central alpha-2 adrenergic receptors. - It is not indicated for the treatment of hyperprolactinemia; in fact, **methyldopa can cause hyperprolactinemia** as a side effect. *Estrogen* - **Estrogen** therapy is sometimes used in women with irregular menses, but it would not address the underlying hyperprolactinemia. - In fact, **estrogen can stimulate prolactin secretion**, potentially worsening the condition and should be avoided in patients with prolactinomas. *L-thyroxine* - **L-thyroxine** is used to treat **hypothyroidism**, which the patient has (subclinical), but it will not directly address the symptoms related to hyperprolactinemia (headaches, irregular menses, elevated prolactin). - While severe primary hypothyroidism can sometimes cause secondary hyperprolactinemia via TRH stimulation, this patient's **subclinical hypothyroidism** is unlikely to be the primary cause of her significantly elevated prolactin and symptoms. - The **most appropriate therapy** targets the hyperprolactinemia directly. *Metoclopramide* - **Metoclopramide** is a **dopamine antagonist** used as an antiemetic and prokinetic agent. - It **increases prolactin secretion** by blocking dopamine D2 receptors in the pituitary, which would significantly exacerbate the patient's hyperprolactinemia.

Question 212: A 4-year-old boy with a history of cerebral palsy is brought to the neurology clinic by his mother with progressive tightness in the lower extremities. Although the patient has been intermittently undergoing physiotherapy for the past 2 years at a specialized center, the patient’s mother is concerned he cannot yet climb the stairs. The neurologist recommends a different treatment, which involves multiple intramuscular injections of a drug in the muscles of the lower extremities to relieve tightness. The neurologist says this treatment approach is also often used to relieve headaches and reduce facial wrinkles. Which of the following is most likely the mechanism of action of this drug?

A. Interferes with the 60s ribosomal subunit
B. Blocks the release of acetylcholine (Correct Answer)
C. Reduces neurotransmitter GABA
D. Acts as a superantigen
E. Stimulates adenylate cyclase

Explanation: ***Blocks the release of acetylcholine*** - The scenario describes **botulinum toxin**, which is used to treat **spasticity** in cerebral palsy, as well as for cosmetic purposes (reducing facial wrinkles) and chronic migraine prophylaxis - Botulinum toxin works by **cleaving SNARE proteins** (synaptobrevin, syntaxin, SNAP-25) necessary for fusion of acetylcholine-containing vesicles with the presynaptic membrane - This prevents **acetylcholine release** at the neuromuscular junction, causing localized muscle paralysis and relieving spasticity - The drug is administered via **multiple intramuscular injections** directly into affected muscles *Interferes with the 60s ribosomal subunit* - This mechanism is associated with certain **antibiotics** like macrolides (erythromycin) or clindamycin, which inhibit bacterial protein synthesis - Not relevant to muscle spasticity treatment or the described clinical uses *Reduces neurotransmitter GABA* - Drugs that reduce **GABAergic signaling** would increase neuronal excitability and potentially worsen muscle tone - This would **exacerbate spasticity**, not relieve it - Examples include flumazenil (GABA antagonist) *Acts as a superantigen* - **Superantigens** are bacterial toxins (e.g., from Staphylococcus aureus, Streptococcus pyogenes) that stimulate massive, non-specific T-cell activation - Lead to conditions like toxic shock syndrome - Completely unrelated to the mechanism for treating muscle spasticity *Stimulates adenylate cyclase* - Stimulation of **adenylate cyclase** increases intracellular cAMP levels - This is the mechanism of various drugs including beta-adrenergic agonists and certain hormones - Not associated with the localized muscle relaxation achieved by botulinum toxin

Question 213: A 63-year-old woman presents to her primary care doctor with increased urinary frequency. She has noticed that over the past 6 months, she has had to urinate more often than usual. Several times per day, she develops a rapid-onset need to urinate and has occasionally been unable to reach the restroom. These symptoms have caused her a lot of distress and impacted her work as a grocery store clerk. She has tried pelvic floor exercises, decreasing her caffeine consumption, and has intentionally lost 20 pounds in an effort to alleviate her symptoms. She denies urinary hesitancy or hematuria. Her past medical history is notable for rheumatoid arthritis for which she takes methotrexate. She does not smoke or drink alcohol. Her temperature is 98.8°F (37.1°C), blood pressure is 124/68 mmHg, pulse is 89/min, and respirations are 19/min. She is well-appearing and in no acute distress. Which of the following interventions would be most appropriate in this patient?

A. Intermittent catheterization
B. Tamsulosin
C. Topical estrogen
D. Pessary placement
E. Oxybutynin (Correct Answer)

Explanation: ***Oxybutynin*** - The patient presents with classic symptoms of **overactive bladder**, including increased urinary frequency, urgency, and urge incontinence, which have not responded to behavioral modifications. Oxybutynin is an **antimuscarinic medication** that relaxes the detrusor muscle, reducing bladder spasms and urgency. - This medication is a **first-line pharmacological treatment** for overactive bladder syndrome after conservative therapies have failed, making it the most appropriate intervention given her symptoms and history. *Intermittent catheterization* - This intervention is primarily used for **urinary retention** or significant **post-void residual volume**, which are not indicated by the patient's symptoms (she denies urinary hesitancy). - Her symptoms are consistent with bladder overactivity, not an inability to empty her bladder, so catheterization would be inappropriate and potentially harmful. *Tamsulosin* - Tamsulosin is an **alpha-1 adrenergic blocker** typically used to treat symptoms of **benign prostatic hyperplasia (BPH)** in men by relaxing smooth muscle in the prostate and bladder neck. - It is not indicated for overactive bladder in women and would not address her primary symptoms of frequency and urgency. *Topical estrogen* - Topical estrogen can be beneficial for **urogenital atrophy** in postmenopausal women, which can contribute to urinary symptoms, particularly stress incontinence or dysuria. - While she is a 63-year-old woman, her symptoms are clearly indicative of **urge incontinence** and overactive bladder, which are less likely to be solely improved by estrogen, especially given the severity and associated urgency. *Pessary placement* - Pessaries are used for **pelvic organ prolapse** or **stress urinary incontinence** to provide structural support or compress the urethra. - The patient's primary complaint is **urge incontinence** and overactive bladder symptoms, not prolapse or stress incontinence, making a pessary an unsuitable intervention.

Question 214: A 25-year-old man is brought to the emergency department 3 hours after rescuing babies and puppies from a burning daycare center. He complains of headache and nausea, which he attributes to running. He is breathing comfortably. What is another likely finding in this patient?

A. Oxygen saturation of 86% on pulse oximetry
B. Low blood lactate levels
C. Arterial oxygen partial pressure of 20 mmHg
D. Oxygen saturation of 99% on pulse oximetry
E. Cherry red facial appearance (Correct Answer)

Explanation: ***Cherry red facial appearance*** - The patient's presentation after being in a burning building strongly suggests **carbon monoxide (CO) poisoning**. CO binds to hemoglobin with higher affinity than oxygen, forming **carboxyhemoglobin**, which gives the skin and mucous membranes a characteristic **cherry-red (plethoric) appearance**, though this is often only seen in severe cases or post-mortem. - Other symptoms like **headache and nausea** are classic for CO poisoning, often mistaken for other mild ailments or exertion. *Oxygen saturation of 86% on pulse oximetry* - While a low oxygen saturation is concerning, **pulse oximetry readings are unreliable in carbon monoxide poisoning** because standard pulse oximeters cannot differentiate between oxyhemoglobin and carboxyhemoglobin. - A patient with significant CO poisoning can have a high pulse oximetry reading even with severe hypoxemia at the tissue level, making this an unlikely and misleading finding. *Low blood lactate levels* - **Carbon monoxide poisoning** leads to **tissue hypoxia**, which switches cellular metabolism from aerobic to anaerobic glycolysis. - This results in the overproduction of **lactate**, leading to **elevated blood lactate levels**, not low levels. *Arterial oxygen partial pressure of 20 mmHg* - A **PaO2 of 20 mmHg** is severely low and would indicate extreme hypoxemia, which would likely present with significant respiratory distress or altered mental status, and a pulse oximetry reading would be reflective of this severe hypoxemia. - In **carbon monoxide poisoning**, the PaO2 is typically normal because oxygen can still dissolve in the plasma, but its transport and offloading are impaired by carboxyhemoglobin. *Oxygen saturation of 99% on pulse oximetry* - A pulse oximeter measures the percentage of hemoglobin saturated with oxygen. However, it cannot distinguish between **oxyhemoglobin** and **carboxyhemoglobin**. - Therefore, in CO poisoning, pulse oximetry may give a **falsely high or normal reading (e.g., 99%)**, even when the patient is severely hypoxic due to CO.

Question 215: A 7-year-old boy is brought to the physician because of spells of unresponsiveness and upward rolling of the eyes for 2 months. The episodes start abruptly and last a few seconds. During that time he does not hear anyone’s voice or make any purposeful movements. When the episodes end, he continues what he was doing before the spell. He does not lose his posture or fall to the ground. Episodes occur multiple times during the day. Physical examination shows no abnormal findings. An EEG following hyperventilation shows 3 Hz spike-and-slow-wave discharges. Which of the following is the most appropriate pharmacotherapy at this time?

A. No pharmacotherapy at this time
B. Ethosuximide (Correct Answer)
C. Sodium valproate
D. Oxcarbazepine
E. Lamotrigine

Explanation: ***Ethosuximide*** - The described clinical picture (brief unresponsiveness, eye-rolling, continuing activity afterward, frequent daily episodes, normal physical exam, and 3-Hz spike-and-slow-wave discharges on EEG during hyperventilation) is classic for **childhood absence epilepsy**. - **Ethosuximide** is the first-line and most effective treatment specifically for absence seizures due to its selective action on T-type calcium channels in the thalamus, which are implicated in the generation of absence seizures. *No pharmacotherapy at this time* - Leaving childhood absence epilepsy untreated can lead to significant impairments in learning, attention, and cognitive development due to the frequent, brief interruptions in consciousness. - Given the clear diagnostic criteria including characteristic EEG findings and frequent episodes, initiating appropriate pharmacotherapy is medically indicated and crucial for the child's well-being. *Sodium valproate* - While **sodium valproate** is effective against absence seizures and has a broader spectrum of action against other seizure types, it is often considered a second-line agent for absence epilepsy due to potential side effects. - Its use may be preferred if there are co-occurring generalized tonic-clonic seizures or if ethosuximide is not tolerated or effective, but for isolated absence seizures, ethosuximide has a better side effect profile. *Oxcarbazepine* - **Oxcarbazepine** is a sodium channel blocker primarily used for focal (partial onset) seizures and secondarily generalized tonic-clonic seizures. - It is generally ineffective and can sometimes *worsen* absence seizures, making it an inappropriate choice for this diagnosis. *Lamotrigine* - **Lamotrigine** is a broad-spectrum antiepileptic drug effective for various seizure types, including focal, generalized tonic-clonic, and some forms of atypical absence seizures. - While it can be used for absence seizures, it is generally considered a second-line or add-on therapy, especially when ethosuximide or valproate are ineffective or not tolerated, or if there are co-existing seizure types. It is not the most appropriate first-line choice for classic childhood absence epilepsy.

Question 216: A 34-year-old man presents to the outpatient clinic with a complaint of right-sided jaw pain. The onset of pain was approx. 1 month ago and he is experiencing symptoms 2–3 times a day. Each episode of pain lasts for about 30 seconds. He describes the pain as severe (9 out of 10) with an electric and sharp quality. He denies having tear production or conjunctival injection on the affected side during attacks. What is the mechanism of action for the drug that will best treat this patient’s condition?

A. Increase the time of Cl- channel opening
B. Prevention of Na+ influx (Correct Answer)
C. Decrease the excitatory effects of glutamic acid
D. Decrease in the Ca2+ influx
E. Increase the frequency of Cl- channel opening

Explanation: ***Prevention of Na+ influx*** - The patient's symptoms (right-sided jaw pain, severe, electric, sharp quality, short duration, triggered by daily activities like chewing/talking) are highly consistent with **trigeminal neuralgia**. - **Carbamazepine**, a sodium channel blocker, is the first-line treatment for trigeminal neuralgia, and its mechanism of action involves **preventing Na+ influx** in neural membranes, thus stabilizing the excited nerve. *Increase the time of Cl- channel opening* - This mechanism is associated with **benzodiazepines**, which act on GABA-A receptors to enhance the inhibitory effects of GABA by **increasing the duration of Cl- channel opening**. - While benzodiazepines can have anticonvulsant properties, they are not the primary treatment for trigeminal neuralgia because **carbamazepine is more effective** at specifically targeting the hyperexcitability of the trigeminal nerve. *Decrease the excitatory effects of glutamic acid* - This mechanism is characteristic of drugs like **memantine** (used in Alzheimer's disease) or some antiglutamatergic agents in epilepsy. - While glutamatergic overactivity can contribute to pain, **inhibiting glutamate receptors** is not the primary or most effective strategy for the acute symptomatic relief in trigeminal neuralgia. *Decrease in the Ca2+ influx* - This mechanism is seen with **calcium channel blockers** like gabapentin and pregabalin, which can be used as second-line treatments for neuropathic pain including trigeminal neuralgia. - However, **sodium channel blockade** (e.g., carbamazepine) is considered more direct and effective for the high-frequency firing characteristic of trigeminal neuralgia. *Increase the frequency of Cl- channel opening* - This mechanism also involves **GABA-A receptor agonists** like benzodiazepines, but specifically some agents might increase the frequency of chloride channel opening rather than duration or both. - Similar to increasing the time of Cl- channel opening, this mechanism aims to enhance GABAergic inhibition but is **not the primary mechanism of action** for the most effective drug in trigeminal neuralgia.

Question 217: A new drug is designed to treat asthma by inhibiting bronchoconstriction. Experimental assays show that treated animals had markedly reduced acetylcholine binding to muscarinic receptors relative to untreated controls. The drug is most similar to which of the following:

A. Theophylline
B. Cromolyn
C. Zafirlukast
D. Prednisone
E. Ipratropium (Correct Answer)

Explanation: ***Ipratropium*** - This drug works as a **muscarinic acetylcholine receptor antagonist**, blocking the bronchoconstrictive effects of acetylcholine release in the airways. - The experimental assay showing reduced **acetylcholine binding to muscarinic receptors** directly mimics the mechanism of action of ipratropium. *Theophylline* - Theophylline is a **phosphodiesterase inhibitor**, leading to increased cyclic AMP and bronchodilation, but it does not directly interfere with acetylcholine binding to muscarinic receptors. - Its mechanism also involves adenosine receptor antagonism. *Cromolyn* - Cromolyn is a **mast cell stabilizer** that prevents the release of inflammatory mediators like histamine, thereby preventing bronchoconstriction. - It does not act on muscarinic receptors. *Zafirlukast* - Zafirlukast is a **leukotriene receptor antagonist**, blocking the actions of leukotrienes which are potent bronchoconstrictors and pro-inflammatory mediators. - Its mechanism is distinct from muscarinic receptor antagonism. *Prednisone* - Prednisone is a **corticosteroid** that reduces inflammation by inhibiting the synthesis of inflammatory mediators and altering gene expression. - It does not directly affect acetylcholine binding at muscarinic receptors.

Question 218: In patients with chronic obstructive pulmonary disease, stimulation of muscarinic acetylcholine receptors results in an increase in mucus secretion, smooth muscle contraction and bronchoconstriction. The end result is an increase in airway resistance. Which of the following pharmacologic agents interferes directly with this pathway?

A. Epinephrine
B. Albuterol
C. Theophylline
D. Ipratropium (Correct Answer)
E. Metoprolol

Explanation: ***Ipratropium*** - **Ipratropium** is an **anticholinergic** agent that blocks muscarinic acetylcholine receptors. - By blocking these receptors, it **reduces bronchoconstriction**, mucus secretion, and smooth muscle contraction, thus decreasing airway resistance. *Epinephrine* - **Epinephrine** is a non-selective **adrenergic agonist** that stimulates both alpha and beta receptors. - Its effects in the airways are primarily mediated through **beta-2 agonism**, leading to bronchodilation, but it does not directly interfere with muscarinic pathways. *Albuterol* - **Albuterol** is a **short-acting beta-2 adrenergic agonist (SABA)**. - It primarily causes bronchodilation by stimulating beta-2 receptors on airway smooth muscle, independent of the muscarinic pathway. *Theophylline* - **Theophylline** is a **methylxanthine** that primarily acts as a non-selective phosphodiesterase inhibitor. - This leads to increased intracellular **cAMP** and bronchodilation, but it does not directly block muscarinic acetylcholine receptors. *Metoprolol* - **Metoprolol** is a **selective beta-1 adrenergic blocker** (beta-blocker). - Its primary action is on the heart; it has minimal effect on airway beta-2 receptors at therapeutic doses due to its selectivity, and it does not interfere with the muscarinic pathway.

Question 219: A 43-year-old man is brought to the emergency department by his wife because of a 1-hour history of confusion and strange behavior. She reports that he started behaving in an agitated manner shortly after eating some wild berries that they had picked during their camping trip. His temperature is 38.7°C (101.7°F). Physical examination shows warm, dry skin and dry mucous membranes. His pupils are dilated and minimally reactive to light. His bowel sounds are decreased. The patient is admitted and pharmacotherapy is initiated with a drug that eventually results in complete resolution of all of his symptoms. This patient was most likely administered which of the following drugs?

A. Rivastigmine
B. Atropine
C. Scopolamine
D. Physostigmine (Correct Answer)
E. Neostigmine

Explanation: ***Physostigmine*** - The patient's symptoms (confusion, agitation, dilated pupils, warm/dry skin, decreased bowel sounds, fever) are characteristic of **anticholinergic toxicity**, often caused by ingestion of plants like Jimson weed or deadly nightshade (containing atropine-like alkaloids). - **Physostigmine** is a **reversible acetylcholinesterase inhibitor** that can cross the **blood-brain barrier** and reverse both central (confusion, agitation) and peripheral (dilated pupils, dry skin, decreased bowel sounds) anticholinergic effects. *Rivastigmine* - **Rivastigmine** is an acetylcholinesterase inhibitor primarily used to treat **Alzheimer's disease** and Parkinson's disease dementia. - While it inhibits acetylcholinesterase, its primary clinical use and efficacy profile do not align with rapid reversal of acute, severe anticholinergic poisoning. *Atropine* - **Atropine** is a **muscarinic anticholinergic agent** that would *exacerbate* the patient's symptoms, as the presentation is consistent with anticholinergic poisoning. - It works by blocking acetylcholine receptors, leading to effects like dilated pupils, dry mouth, and decreased gastrointestinal motility. *Scopolamine* - **Scopolamine** is another potent **muscarinic anticholinergic agent** that causes similar symptoms to atropine, particularly confusion and delirium due to its central nervous system effects. - Administering scopolamine would worsen the patient's existing anticholinergic toxidrome. *Neostigmine* - **Neostigmine** is a **reversible acetylcholinesterase inhibitor** used for conditions like myasthenia gravis and reversal of neuromuscular blockade. - However, **neostigmine does not cross the blood-brain barrier** effectively, meaning it would not reverse the central nervous system symptoms (confusion, agitation) prominent in this anticholinergic poisoning case.

Question 220: A 24-year-old man is brought to the emergency department by his roommates for aggressive and unusual behavior. His roommates state that he has been under a lot of stress lately from his final exams and has been more reclusive. They state that this evening he was very irritable and was yelling at his computer prior to breaking it, followed by him spending several hours at the gym. His temperature is 101°F (38.3°C), blood pressure is 137/98 mmHg, pulse is 120/min, respirations are 23/min, and oxygen saturation is 99% on room air. Physical exam is notable for an irritable young man. Cardiopulmonary exam is notable for tachycardia and bilateral clear breath sounds. Neurological exam reveals dilated pupils. The patient is notably diaphoretic and speaks very rapidly during the physical exam and is aggressive. He is given haloperidol, diphenhydramine, and diazepam for sedation and placed in soft restraints. His symptoms resolved over the next 10 hours in the emergency department. Which of the following is the most likely diagnosis?

A. Cocaine intoxication (Correct Answer)
B. Phencyclidine intoxication
C. Schizophrenia
D. Caffeine intoxication
E. Lisdexamfetamine intoxication

Explanation: ***Cocaine intoxication*** - The patient's presentation with **agitation, aggression, dilated pupils, tachycardia, hypertension, diaphoresis, and rapid speech** is highly consistent with stimulant intoxication, especially **cocaine**. - The **rapid resolution of symptoms over 10 hours** supports cocaine intoxication, as cocaine has a short half-life (~1 hour) with effects typically resolving within a few hours after cessation. *Phencyclidine intoxication* - While PCP can cause aggression, agitation, and dilated pupils, it is classically associated with **nystagmus (horizontal or vertical)**, which is not mentioned here. - PCP intoxication often presents with **dissociative symptoms** and a severe level of unpredictable violence or bizarre behavior not fully described. *Schizophrenia* - The **acute onset of symptoms** in a previously functioning individual, particularly with a clear trigger (stress), is less typical for schizophrenia, which usually has a more insidious prodromal phase. - The **rapid and complete resolution** of symptoms within hours strongly argues against a primary psychotic disorder like schizophrenia, which requires longer-term treatment. *Caffeine intoxication* - While high doses of caffeine can cause **tachycardia, anxiety, and agitation**, it rarely leads to the severe **aggression and property damage** described in this case. - The degree of physical symptoms like **dilated pupils, hypertension, and significant diaphoresis** would be unusually severe for typical caffeine intoxication. *Lisdexamfetamine intoxication* - Lisdexamfetamine (Vyvanse) is an amphetamine prodrug that shares many symptoms with cocaine intoxication, including **agitation, aggression, dilated pupils, and sympathetic overdrive**. - However, amphetamines have a **much longer duration of action (8-12+ hours)** compared to cocaine, so complete symptom resolution within 10 hours would be less typical for amphetamine intoxication, which often requires longer observation periods.

Question 221: A 65-year-old man presents to the emergency department with confusion and a change in his behavior. The patient was in his usual state of health 3 days ago. He became more confused and agitated this morning thus prompting his presentation. The patient has a past medical history of depression, hypertension, diabetes, and Parkinson disease and is currently taking fluoxetine, lisinopril, insulin, metformin, and selegiline (recently added to his medication regimen for worsening Parkinson symptoms). He also takes oxycodone and clonazepam for pain and anxiety; however, he ran out of these medications last night. His temperature is 101°F (38.3°C), blood pressure is 111/78 mmHg, pulse is 117/min, respirations are 22/min, and oxygen saturation is 99% on room air. Physical exam is notable for an irritable, sweaty, and confused elderly man. Neurological exam reveals hyperreflexia of the lower extremities and clonus. Which of the following is the most likely etiology of this patient’s symptoms?

A. Electrolyte abnormality
B. Medication complication (Correct Answer)
C. Viral infection
D. Substance withdrawal
E. Bacterial infection

Explanation: ***Medication complication*** - The combination of **fluoxetine** and **selegiline** can precipitate **serotonin syndrome**, characterized by altered mental status, autonomic dysfunction (fever, tachycardia, sweating), and neuromuscular hyperactivity (hyperreflexia, clonus). - Both medications increase serotonin levels in the central nervous system; fluoxetine is a selective serotonin reuptake inhibitor (SSRI), and selegiline is a monoamine oxidase type B (MAO-B) inhibitor that, at higher doses, can also inhibit MAO-A, leading to increased serotonin. *Electrolyte abnormality* - While electrolyte imbalances can cause confusion and altered mental status, they typically do not present with the specific constellation of fever, tachycardia, sweating, hyperreflexia, and clonus seen here. - There is no specific information in the clinical presentation to suggest an electrolyte imbalance is the primary cause over a medication-induced syndrome. *Viral infection* - Viral infections can cause fever and confusion, but the rapid onset and the specific neurological findings of marked **hyperreflexia** and **clonus** are more indicative of a central nervous system (CNS) disturbance like serotonin syndrome rather than a typical viral encephalopathy or infection. - The absence of other common viral symptoms (e.g., cough, sore throat, GI symptoms) makes it less likely. *Substance withdrawal* - Withdrawal from **oxycodone** (opioid) or **clonazepam** (benzodiazepine) could cause agitation and autonomic symptoms. However, opioid withdrawal typically causes diarrhea, nausea, vomiting, and muscle aches, not hyperreflexia or fever, and benzodiazepine withdrawal usually presents with seizures, anxiety, and tremors, but the hyperreflexia and clonus point more strongly to serotonin syndrome, especially given the medication history. - The patient ran out of these medications the previous night, which could contribute to some symptoms but doesn't fully explain the specific neurological signs in the context of the recent medication change. *Bacterial infection* - A bacterial infection could cause fever and confusion, but typically less specific neurological signs like **hyperreflexia** and **clonus** are not characteristic. - While a CNS infection like meningitis could present with altered mental status and fever, it would usually involve neck stiffness and specific CSF findings, which are not mentioned.

Question 222: A 50-year-old woman presents with altered taste and a gritty sensation in her eyes for the last month. She mentions that she needs to drink water frequently and often feels that her mouth and throat are dry. On physical examination, she has bilateral enlargement of the parotid glands and dry conjunctivae. Her physical examination and laboratory findings suggest a diagnosis of sicca syndrome. In addition to non-pharmacological measures, a drug is prescribed to improve symptoms related to dryness of mouth by increasing salivation. Which of the following is the mechanism of action of the drug that most likely is being prescribed to this patient?

A. Selective M2 muscarinic receptor agonist
B. Selective M3 muscarinic receptor agonist (Correct Answer)
C. Selective M2 muscarinic receptor antagonist
D. Selective M3 muscarinic receptor antagonist
E. Selective M1 muscarinic receptor antagonist

Explanation: ***Selective M3 muscarinic receptor agonist*** - **Pilocarpine** or **cevimeline**, M3 muscarinic receptor agonists, are commonly used for **sicca symptoms** in Sjögren's syndrome. - Activation of **M3 receptors** on salivary and lacrimal glands directly stimulates increased **saliva** and **tear production**. *Selective M2 muscarinic receptor agonist* - **M2 receptors** are primarily found in the **heart**, and their activation would primarily affect **cardiac function** (e.g., bradycardia), not salivary secretion. - While M2 receptors are G protein-coupled, their role in exocrine gland secretion is minimal compared to M3. *Selective M2 muscarinic receptor antagonist* - An **M2 antagonist** would primarily cause an **increase in heart rate** by blocking parasympathetic input to the heart. - Such a drug would have no direct positive effect on saliva production and could worsen dry mouth by its indirect effects. *Selective M3 muscarinic receptor antagonist* - An **M3 antagonist** would **block salivary and tear production**, exacerbating the patient's dry mouth and gritty eyes. - These drugs are typically used to treat conditions like overactive bladder (e.g., darifenacin) or chronic obstructive pulmonary disease (e.g., tiotropium). *Selective M1 muscarinic receptor antagonist* - **M1 receptors** are predominantly found in the **cerebral cortex** and **gastric glands**. - An M1 antagonist would primarily affect cognitive function or gastric acid secretion, which is not the therapeutic goal here.

Question 223: A 19-year-old male presents to the ER with generalized tonic-clonic seizures. He does not have a prior history of seizures and has not taken any drugs except for his daily asthma medication. Which of the following is associated with seizures?

A. Albuterol
B. Prednisone
C. Cromolyn
D. Theophylline (Correct Answer)
E. Ipratropium

Explanation: ***Theophylline*** - **Theophylline** has a narrow therapeutic index, and its toxicity can manifest as **seizures** and cardiac arrhythmias, especially in a patient with no prior seizure history. - While used for asthma, uncontrolled or high doses can lead to systemic effects including neurological complications like **seizures**. *Albuterol* - **Albuterol** is a beta-2 agonist and is generally well-tolerated at therapeutic doses, with common side effects being **tremor** and **tachycardia**. - While overdose can cause cardiotoxicity, it is less commonly associated with **seizures** as a primary side effect compared to theophylline. *Prednisone* - **Prednisone**, a corticosteroid, can have psychiatric side effects like mood changes and psychosis, but **generalized tonic-clonic seizures** are a rare complication. - Seizures are more likely to be associated with steroid withdrawal or very high doses in susceptible individuals, which is not clearly indicated here. *Cromolyn* - **Cromolyn** is a mast cell stabilizer used for asthma prevention and is known for its excellent safety profile, with very few systemic side effects. - It is not associated with **seizures** or other severe neurological complications. *Ipratropium* - **Ipratropium** is an anticholinergic bronchodilator primarily used for asthma and COPD. Systemic absorption is minimal, so systemic side effects are rare. - While high doses can cause anticholinergic effects, **seizures** are not a typical or common adverse event associated with its use.

Question 224: A 36-year-old man is admitted to the hospital for treatment of burn wounds on his upper extremities. Analgesic therapy with an opioid drug is begun. Shortly after, the patient develops chills, diaphoresis, nausea, and abdominal pain. On further questioning, the patient reports that he has been smoking opium at home to help him ""deal with the depression and pain.” This patient was most likely given which of the following opioid drugs?

A. Butorphanol (Correct Answer)
B. Oxycodone
C. Morphine
D. Fentanyl
E. Hydrocodone

Explanation: ***Butorphanol*** - **Butorphanol** is a **mixed opioid agonist-antagonist** that acts as a **kappa (κ) receptor agonist** and **mu (μ) receptor antagonist/partial agonist**. - In opioid-dependent patients who use **mu receptor agonists** (like opium), butorphanol can precipitate **acute opioid withdrawal** by displacing full agonists from mu receptors and blocking their effects. - The patient's symptoms of chills, diaphoresis, nausea, and abdominal pain are classic signs of **acute opioid withdrawal syndrome**. *Oxycodone* - **Oxycodone** is a **full mu opioid receptor agonist** and would not precipitate withdrawal in an opioid-dependent patient. - Administering oxycodone would provide continued mu receptor stimulation, potentially alleviating withdrawal symptoms or maintaining the patient's opioid dependence. *Morphine* - **Morphine** is a **full mu opioid receptor agonist** and would not cause withdrawal in an opioid-dependent individual. - It would continue to stimulate mu opioid receptors, providing analgesia and preventing withdrawal symptoms. *Fentanyl* - **Fentanyl** is a potent **full mu opioid receptor agonist** and would provide continued opioid receptor stimulation. - Its administration would prevent withdrawal and provide effective analgesia in an opioid-tolerant patient. *Hydrocodone* - **Hydrocodone** is a **full mu opioid receptor agonist** and would not induce withdrawal symptoms. - Like other full agonists, it would continue mu receptor activation, providing analgesia without precipitating withdrawal.

Question 225: A 16 year-old female is being evaluated for shortness of breath. For the last year she has had shortness of breath and subjective wheezing with exercise and intermittent coughing at night. She reports waking up from sleep coughing 1-2 times per month. She now skips gym class because of her symptoms. She denies any coughing, chest tightness, or shortness of breath on the day of her visit. On exam, her lungs are clear to auscultation bilaterally, with normal inspiratory to expiratory duration ratio. Her pulmonary function tests (PFTs) show normal FEV1 and FVC based on her age, gender, and height. She is told to inhale a medication, and her PFTs are repeated, now showing a FEV1 79% of her previous reading. The patient is diagnosed with asthma. Which of the following medications was used to diagnose the patient?

A. Pilocarpine
B. Carbachol
C. Methacholine (Correct Answer)
D. Bethanechol
E. Physostigmine

Explanation: ***Methacholine*** - **Methacholine** is a muscarinic cholinergic agonist that, when inhaled, causes **bronchoconstriction** in susceptible individuals, leading to a decrease in FEV1. - A significant drop in FEV1 (typically 20% or more) after methacholine challenge is diagnostic for **asthma**, especially when baseline PFTs are normal. *Pilocarpine* - **Pilocarpine** is a muscarinic agonist primarily used to treat **glaucoma** (by causing miosis and reducing intraocular pressure) and **dry mouth/eyes**. - It is not used for the diagnosis of asthma through bronchial challenge testing. *Carbachol* - **Carbachol** is a cholinergic agonist with both muscarinic and nicotinic activity, used mainly in ophthalmology to induce **miosis** during surgery. - It is not a standard agent for bronchial provocation testing in asthma diagnosis. *Bethanechol* - **Bethanechol** is a muscarinic agonist used to treat **urinary retention** and reduce symptoms of **gastroesophageal reflux disease (GERD)**. - It is not used for asthma diagnosis. *Physostigmine* - **Physostigmine** is an acetylcholinesterase inhibitor that indirectly increases acetylcholine levels, used as an **antidote for anticholinergic poisoning**. - It is not used as a direct broncho-constrictor for asthma diagnosis.

Question 226: A 32-year-old man with a history of major depressive disorder is brought to the emergency department by his wife because of a sudden onset of restlessness and disorientation that developed 3 hours ago. The patient’s wife says that he suddenly started sweating, having tremors, and mumbling to himself. Yesterday, the patient visited his psychiatrist with worsening depression who added phenelzine to his current treatment regimen. No other significant past medical history. His temperature is 39.7°C (103.5°F), blood pressure is 145/90 mm Hg, and pulse is 115/min. On physical examination, the skin is flushed. Mucous membranes are dry, and pupils are dilated. There is pronounced clonus in the extremities bilaterally. Babinski sign is present bilaterally. All the patient’s medications are discontinued, and intravenous fluids are started. Which of the following drugs most likely interacted with phenelzine to cause this patient’s condition?

A. Sertraline (Correct Answer)
B. Olanzapine
C. Mirtazapine
D. Bupropion
E. Lithium

Explanation: ***Sertraline*** - The patient exhibits classic symptoms of **serotonin syndrome**, including **mental status changes (disorientation, mumbling), autonomic hyperactivity (sweating, fever, flushed skin, tachycardia, hypertension, dry mucous membranes, dilated pupils)**, and **neuromuscular abnormalities (tremors, clonus, Babinski sign)**. - **Sertraline** is an **SSRI** (selective serotonin reuptake inhibitor). The concurrent use of an **SSRI** with **phenelzine**, a **MAOI** (monoamine oxidase inhibitor), can lead to a dangerous overabundance of serotonin in the central nervous system, predictably causing **serotonin syndrome**. - This is a **classic, high-risk drug interaction** that is absolutely contraindicated. *Olanzapine* - **Olanzapine** is an **atypical antipsychotic** primarily used to treat schizophrenia and bipolar disorder, and it does not significantly impact serotonin levels in a way that would precipitate serotonin syndrome when combined with a MAOI. - Its main mechanisms involve antagonism at **dopamine D2 and serotonin 5-HT2A receptors**, and it generally does not elevate serotonin to toxic levels. *Mirtazapine* - **Mirtazapine** is an **alpha-2 adrenergic antagonist** and specific **serotonin receptor antagonist** (5-HT2 and 5-HT3). While it can theoretically interact with MAOIs, it enhances serotonergic transmission indirectly through increased norepinephrine release rather than directly blocking serotonin reuptake. - The risk of serotonin syndrome with mirtazapine + MAOI is **significantly lower than with SSRIs + MAOI**, though caution is still warranted. It would not be the **most likely** cause in this scenario. *Bupropion* - **Bupropion** is a **norepinephrine-dopamine reuptake inhibitor (NDRI)**; it does not significantly affect serotonin levels. - Therefore, it would not interact with **phenelzine** to cause serotonin syndrome. *Lithium* - **Lithium** is a **mood stabilizer** primarily used for bipolar disorder. It has no direct serotonergic mechanism that would interact with a **MAOI** to cause serotonin syndrome. - Its therapeutic effects are thought to be mediated through various intracellular signaling pathways.

Question 227: A neurophysiologist describes the mechanism of a specific type of synaptic transmission to his students. While illustrating this, he points out that when the action potential reaches the presynaptic terminal of a chemical synapse, the voltage-gated Ca2+ channels open. Ca2+ ions trigger the release of neurotransmitters from vesicles in the presynaptic terminal. In this type of synaptic transmission, increased cytosolic Ca2+ levels cause the release of a neurotransmitter from small vesicles with dense cores. Which of the following neurotransmitters is most likely to be the one that is released into the synaptic cleft in this type of synapse?

A. Epinephrine
B. Glutamate
C. Glycine
D. GABA (γ-amino butyric acid)
E. Norepinephrine (Correct Answer)

Explanation: ***Norepinephrine*** - **Norepinephrine** is the primary catecholamine neurotransmitter stored in **small vesicles with dense cores** (dense-core vesicles). - It is released from **sympathetic postganglionic neurons** and central nervous system neurons, particularly from the **locus coeruleus**. - Dense-core vesicles are the hallmark of catecholaminergic neurons, and norepinephrine is the most abundant neuronal catecholamine. - The description perfectly matches noradrenergic synaptic transmission. *Epinephrine* - While epinephrine is also a catecholamine stored in dense-core vesicles, it functions primarily as a **hormone** released from the **adrenal medulla** (not a neurotransmitter). - Only a **very small number** of CNS neurons use epinephrine as a neurotransmitter (mainly in medullary regions). - In the context of synaptic transmission, norepinephrine is far more common. *Glutamate* - **Glutamate** is the primary excitatory neurotransmitter in the CNS but is stored in **small, clear synaptic vesicles**, not dense-core vesicles. - It does not fit the description of dense-core vesicle storage. *Glycine* - **Glycine** is an inhibitory neurotransmitter stored in **small, clear synaptic vesicles**. - Found predominantly in the **spinal cord** and brainstem, not in dense-core vesicles. *GABA (γ-amino butyric acid)* - **GABA** is the main inhibitory neurotransmitter stored in **small, clear synaptic vesicles**. - Not associated with dense-core vesicle storage.

Question 228: A 51-year-old woman presents to your office with 2 weeks of fatigue and generalized weakness. She has a past medical history of diabetes, hypertension, and hyperlipidemia. She was recently diagnosed with rheumatoid arthritis and started on disease-modifying therapy. She states she has felt less able to do things she enjoys and feels guilty she can't play sports with her children. Review of systems is notable for the patient occasionally seeing a small amount of bright red blood on the toilet paper. Laboratory studies are ordered as seen below. Hemoglobin: 12 g/dL Hematocrit: 36% Leukocyte count: 7,700/mm^3 with normal differential Platelet count: 207,000/mm^3 MCV: 110 fL Which of the following is the most likely etiology of this patient's fatigue?

A. Depression
B. Gastrointestinal bleed
C. Iron deficiency
D. Medication side effect
E. Vitamin B12 deficiency (Correct Answer)

Explanation: ***Vitamin B12 deficiency*** - The elevated **MCV (110 fL)** indicates **macrocytic anemia**, which is often caused by a vitamin B12 deficiency, leading to fatigue and weakness. - While other causes of fatigue are present, the specific lab finding of macrocytosis points directly to vitamin B12 deficiency as the most likely cause of her current symptoms. *Depression* - While feelings of guilt, loss of enjoyment, and fatigue could be symptoms of **depression**, the clear **macrocytic anemia** in the lab results points to a distinct physical cause. - Depression is a common comorbidity, especially with chronic diseases like rheumatoid arthritis, but is less likely to be the primary cause of fatigue in the presence of such a dominant lab finding. *Gastrointestinal bleed* - Bright red blood on toilet paper suggests a **lower GI bleed** (e.g., hemorrhoids), but this type of bleed typically leads to **iron deficiency anemia** with a **microcytic MCV** (low MCV), not high MCV. - The patient's hemoglobin and hematocrit are not severely low, making an acute significant bleed less likely to be the sole cause of her profound fatigue and macrocytic anemia. *Iron deficiency* - **Iron deficiency** usually presents with **microcytic anemia** (low MCV), typically less than 80 fL, and often results from chronic blood loss, such as in this patient's reported rectal bleeding. - The presented elevated **MCV of 110 fL** directly contradicts iron deficiency as the primary cause of her fatigue and anemia. *Medication side effect* - While many medications can cause fatigue, there's no specific information provided about new medications that commonly lead to **macrocytic anemia** (e.g., methotrexate without folate supplementation). - Without details on her specific disease-modifying therapy for rheumatoid arthritis and in the presence of a clear finding for macrocytic anemia, medication side effect is a less direct explanation.

Question 229: A 67-year-old man presents to the emergency department with trouble urinating. The patient states that in general he has had difficulty urinating but recently, it has taken significant effort for him to initiate a urinary stream. He finds himself unable to completely void and states he has suprapubic tenderness as a result. These symptoms started suddenly 3 days ago. The patient has a history of benign prostatic hyperplasia, constipation, and diabetes mellitus. His current medications include finasteride, sodium docusate, and hydrochlorothiazide. He recently started taking phenylephrine for seasonal allergies. The patient’s last bowel movement was 2 days ago. His temperature is 99.0°F (37.2°C), blood pressure is 167/98 mmHg, pulse is 90/min, respirations are 14/min, and oxygen saturation is 100% on room air. Physical exam is notable for suprapubic tenderness, and an ultrasound reveals 750 mL of fluid in the bladder. Which of the following is the most likely etiology of this patient’s symptoms?

A. Prostatic adenocarcinoma
B. Medication-induced symptoms (Correct Answer)
C. Constipation
D. Urinary tract infection
E. Worsening benign prostatic hypertrophy

Explanation: ***Medication-induced symptoms*** - The patient recently started **phenylephrine**, an **alpha-1 adrenergic agonist**, which can cause **urethral constriction** and worsen urinary outflow obstruction, especially in patients with BPH. - The **sudden onset** of severe urinary retention, leading to suprapubic tenderness and a distended bladder (750 mL), is highly suggestive of a medication side effect given his existing BPH. *Prostatic adenocarcinoma* - While prostatic adenocarcinoma can cause urinary symptoms, these typically develop **gradually** and are less likely to present with such an acute, severe urinary retention episode. - There are no other features like **weight loss**, **bone pain**, or abnormal **PSA levels** mentioned to suggest malignancy. *Constipation* - Although **severe constipation** can sometimes exacerbate urinary symptoms by physical compression on the bladder, the patient's last bowel movement was 2 days ago, which is not severe enough to cause acute urinary retention of this magnitude. - The primary cause of his urinary symptoms is more likely related to bladder outflow obstruction rather than external compression from constipation. *Urinary tract infection* - A UTI typically presents with symptoms like **dysuria**, **frequency**, **urgency**, **fever**, and **chills**, none of which are prominent here. - While a UTI can cause some urinary difficulty, it's less likely to be the sole cause of such acute and severe urinary retention or a bladder volume of 750 mL without other infection signs. *Worsening benign prostatic hypertrophy* - Although the patient has BPH and is on finasteride, a **sudden dramatic worsening** over 3 days, leading to complete inability to void and a large bladder volume, is less typical for a gradual disease progression. - The acute change points more strongly to an **exacerbating factor**, such as a new medication, rather than a natural progression of BPH.

Question 230: A 62-year-old woman is referred to a tertiary care hospital with a history of diplopia and fatigue for the past 3 months. She has also noticed difficulty in climbing the stairs and combing her hair. She confirms a history of 2.3 kg (5.0 lb) weight loss in the past 6 weeks and constipation. Past medical history is significant for type 2 diabetes mellitus. She has a 50-pack-year cigarette smoking history. Physical examination reveals a blood pressure of 135/78 mm Hg supine and 112/65 while standing, a heart rate of 82/min supine and 81/min while standing, and a temperature of 37.0°C (98.6°F). She is oriented to time and space. Her right upper eyelid is slightly drooped. She has difficulty in abducting the right eye. Pupils are bilaterally equal and reactive to light with accommodation. The corneal reflex is intact. Muscle strength is reduced in the proximal muscles of all 4 limbs, and the lower limbs are affected more when compared to the upper limbs. Deep tendon reflexes are bilaterally absent. After 10 minutes of cycling, the reflexes become positive. Sensory examination is normal. Diffuse wheezes are heard on chest auscultation. Which of the following findings is expected?

A. Thymoma on CT scan of the chest
B. Incremental pattern on repetitive nerve conduction studies (Correct Answer)
C. Periventricular plaques on MRI of the brain
D. Antibodies against muscle-specific kinase
E. Elevated serum creatine kinase

Explanation: ***Incremental pattern on repetitive nerve conduction studies*** - The patient's symptoms (diplopia, fatigue, proximal muscle weakness, absent reflexes that normalize with exercise) are highly suggestive of **Lambert-Eaton myasthenic syndrome (LEMS)**. - LEMS is characterized by impaired acetylcholine release at the neuromuscular junction, which manifests as an **incremental response** (progressively larger muscle action potentials) during high-frequency repetitive nerve stimulation. *Thymoma on CT scan of the chest* - **Thymoma** is strongly associated with **myasthenia gravis**, which typically presents with fluctuating weakness that worsens with activity and improves with rest, unlike the LEMS presentation. - While LEMS can be paraneoplastic, it is most commonly associated with **small cell lung carcinoma**, not thymoma, making this finding less likely. *Periventricular plaques on MRI of the brain* - **Periventricular plaques** are characteristic findings in **multiple sclerosis**, a demyelinating disease of the central nervous system. - Multiple sclerosis presents with diverse neurological deficits, but not typically with this specific pattern of fluctuating muscle weakness and absent deep tendon reflexes that improve with exercise. *Antibodies against muscle-specific kinase* - **Anti-MuSK antibodies** are associated with a specific subtype of **myasthenia gravis**, often presenting with prominent bulbar and respiratory weakness. - While myasthenic syndromes share some features, the specific clinical picture (especially the improvement of reflexes with exercise) points away from standard myasthenia gravis and towards LEMS. *Elevated serum creatine kinase* - **Elevated creatine kinase** is typically seen in **myopathies** (e.g., inflammatory myopathies, muscular dystrophies) where there is direct muscle damage. - In LEMS, the primary defect is at the neuromuscular junction, not within the muscle itself, so creatine kinase levels are usually normal.

Question 231: A 42-year-old woman comes to the physician because of progressive weakness. She has noticed increasing difficulty performing household chores and walking her dog over the past month. Sometimes she feels too fatigued to cook dinner. She has noticed that she feels better after sleeping. She does not have chest pain, shortness of breath, or a history of recent illness. She has no personal history of serious illness and takes no medications. She has smoked two packs of cigarettes daily for 25 years. She appears fatigued. Her temperature is 37°C (98.8°F), pulse is 88/min, and blood pressure is 148/80 mm Hg. Pulse oximetry shows an oxygen saturation of 98% in room air. Bilateral expiratory wheezes are heard at both lung bases. Examination shows drooping of the upper eyelids. There is diminished motor strength in her upper extremities. Her sensation and reflexes are intact. A treatment with which of the following mechanisms of action is most likely to be effective?

A. Stimulation of β2 adrenergic receptors
B. Competitive blocking of the muscarinic receptor
C. Reactivation of acetylcholinesterase
D. Inhibition of acetylcholinesterase (Correct Answer)
E. Removing autoantibodies, immune complexes, and cytotoxic constituents from serum

Explanation: ***Inhibition of acetylcholinesterase*** - The patient's symptoms of **progressive weakness**, **fatigue that improves with rest** (improves after sleeping), **bilateral ptosis (drooping eyelids)**, and **diminished motor strength** are classic signs of **myasthenia gravis**. - **Myasthenia gravis** is an autoimmune disorder where antibodies block or destroy acetylcholine receptors at the neuromuscular junction; inhibiting **acetylcholinesterase** increases acetylcholine availability, improving muscle strength. *Stimulation of B2 adrenergic receptors* - This mechanism is primarily used to treat **bronchospasm** in conditions like **asthma** or **COPD**, corresponding to the expiratory wheezes, but would not address the systemic muscle weakness and ptosis. - While beta-agonists can alleviate respiratory symptoms, they do not target the underlying pathophysiology of **myasthenia gravis**. *Competitive blocking of the muscarinic receptor* - **Muscarinic receptor blockers** like **ipratropium** are used to treat bronchoconstriction, often in **COPD**, by preventing acetylcholine from binding to muscarinic receptors on smooth muscle in the airways. - This mechanism would not improve the skeletal muscle weakness and ptosis seen in **myasthenia gravis**, as these symptoms are related to nicotinic receptors at the neuromuscular junction, not muscarinic receptors. *Reactivation of acetylcholinesterase* - **Reactivation of acetylcholinesterase** would lead to a more rapid breakdown of acetylcholine, further *reducing* its availability at the neuromuscular junction. - This action would worsen the symptoms of **myasthenia gravis** by further impairing neuromuscular transmission. *Removing autoantibodies, immune complexes, and cytotoxic constituents from serum* - This describes **plasmapheresis** (plasma exchange), which is a rapid, temporary treatment for myasthenia gravis, particularly during myasthenic crisis or before surgery. - While effective in severe cases by reducing circulating antibodies, it's not the primary or initial mechanism of action for *pharmacological* therapy, which usually involves **acetylcholinesterase inhibitors** or immunotherapy.

Question 232: In an attempt to create other selective dopamine 1 (D1) agonists, a small pharmaceutical company created a cell-based chemical screen that involved three modified receptors - alpha 1 (A1), beta 1 (B1), and D1. In the presence of D1 stimulation, the cell would produce an mRNA that codes for a fluorescent protein; however, if the A1 or B1 receptors are also stimulated at the same time, the cells would degrade the mRNA of the fluorescent protein thereby preventing it from being produced. Which of the following would best serve as a positive control for this experiment?

A. Fenoldopam (Correct Answer)
B. Dobutamine
C. Epinephrine
D. Bromocriptine
E. Dopamine

Explanation: ***Fenoldopam*** - **Fenoldopam** is a selective **D1 dopamine receptor agonist** with minimal affinity for alpha-adrenergic receptors and no significant beta-adrenergic activity. - Its selectivity for D1 receptors means it would stimulate only D1, leading to **fluorescent protein mRNA production** without triggering degradation via A1 or B1 pathways, serving as an ideal positive control for D1 stimulation. *Dobutamine* - **Dobutamine** is a **beta-1 adrenergic receptor agonist**, primarily used to increase cardiac contractility. - Its strong B1 activity would lead to degradation of the fluorescent protein mRNA, making it unsuitable as a positive control for D1 stimulation. *Epinephrine* - **Epinephrine** (adrenaline) is a potent agonist at **alpha-1, alpha-2, beta-1, and beta-2 adrenergic receptors**. - Its broad receptor activation, including A1 and B1, would cause the degradation of the fluorescent protein mRNA, thus failing to act as a positive control for D1. *Bromocriptine* - **Bromocriptine** is primarily a **D2 dopamine receptor agonist**, used in conditions like Parkinson's disease and hyperprolactinemia. - It has minimal or no affinity for D1, A1, or B1 receptors at therapeutic concentrations, so it would not induce fluorescent protein mRNA production, nor would it cause its degradation. *Dopamine* - **Dopamine** acts on multiple receptors, including **D1, D2, alpha-1, and beta-1 adrenergic receptors** in a dose-dependent manner. - Its concurrent stimulation of D1, A1, and B1 receptors would lead to both mRNA production and subsequent degradation, making it difficult to isolate D1 activity and therefore not an ideal positive control here.

Question 233: A 48-year-old man is unable to pass urine after undergoing open abdominal surgery. His physical examination and imaging findings suggest that the cause of his urinary retention is non-obstructive and is most probably due to urinary bladder atony. He is prescribed a new selective muscarinic (M3) receptor agonist, which improves his symptoms. Which of the following is most likely involved in the mechanism of action of this new drug?

A. Activation of phospholipase C (Correct Answer)
B. Inhibition of guanylyl cyclase
C. Inhibition of adenylyl cyclase
D. Increased transmembrane K+ conductance
E. Increased transmembrane Na+ conductance

Explanation: ***Activation of phospholipase C*** - **M3 receptors** are Gq protein-coupled receptors, and their activation leads to the stimulation of **phospholipase C**. - **Phospholipase C** hydrolyzes **phosphatidylinositol 4,5-bisphosphate (PIP2)** into **inositol trisphosphate (IP3)** and **diacylglycerol (DAG)**, which ultimately increases intracellular Ca2+ and causes smooth muscle contraction in the bladder. *Inhibition of guanylyl cyclase* - **Guanylyl cyclase** is typically modulated by other pathways, such as **nitric oxide (NO)**, leading to cGMP production and smooth muscle relaxation. - Its inhibition would not be the primary mechanism for a muscarinic M3 agonist aiming to contract the bladder. *Inhibition of adenylyl cyclase* - **Adenylyl cyclase** is typically inhibited by Gi-coupled receptors (e.g., M2 receptors) leading to a decrease in cAMP and muscle relaxation, which is the opposite effect desired in bladder atony. - M3 receptors, which are Gq-coupled, do not directly inhibit adenylyl cyclase. *Increased transmembrane K+ conductance* - **Increased K+ conductance** typically leads to hyperpolarization and relaxation of smooth muscle, which would worsen bladder atony rather than improve it. - This mechanism is not associated with direct M3 receptor activation. *Increased transmembrane Na+ conductance* - While Na+ channels play a role in neuronal excitability, a direct effect on **transmembrane Na+ conductance** is not the primary mechanism of action for M3 receptor agonists in causing bladder smooth muscle contraction. - Smooth muscle contraction primarily involves **calcium influx and release**.

Question 234: A 31-year-old woman is brought to the physician because of increasing restlessness over the past 2 weeks. She reports that she continuously paces around the house and is unable to sit still for more than 10 minutes at a time. During this period, she has had multiple episodes of anxiety with chest tightness and shortness of breath. She was diagnosed with a psychotic illness 2 months ago. Her current medications include haloperidol and a multivitamin. She appears agitated. Vital signs are within normal limits. Physical examination shows no abnormalities. The examination was interrupted multiple times when she became restless and began to walk around the room. To reduce the likelihood of the patient developing her current symptoms, a drug with which of the following mechanisms of action should have been prescribed instead of her current medication?

A. H2 receptor antagonism
B. 5-HT2A receptor antagonism (Correct Answer)
C. α2 receptor antagonism
D. NMDA receptor antagonism
E. GABA receptor antagonism

Explanation: ***5-HT2A receptor antagonism*** - The patient is experiencing **akathisia**, a common extrapyramidal side effect of **typical antipsychotics** like haloperidol, characterized by subjective or objective motor restlessness. - Atypical antipsychotics, which exert their antipsychotic effects primarily through **5-HT2A receptor antagonism** along with D2 receptor antagonism, have a lower propensity to cause extrapyramidal symptoms, including akathisia, compared to typical antipsychotics. *H2 receptor antagonism* - **H2 receptor antagonists** are primarily used to reduce gastric acid secretion in conditions like peptic ulcer disease and GERD. - They have no direct role in treating psychosis or preventing extrapyramidal side effects. *α2 receptor antagonism* - **Alpha-2 receptor antagonists** (e.g., mirtazapine) are typically used as antidepressants; their mechanism involves increasing norepinephrine and serotonin release. - This mechanism is not directly therapeutic for psychosis and would not prevent akathisia caused by D2 receptor blockade. *NMDA receptor antagonism* - **NMDA receptor antagonists** (e.g., ketamine, memantine) are studied for various neurological and psychiatric conditions, but their primary use is not in typical psychosis treatment, nor do they prevent akathisia from antipsychotics. - Instead, NMDA receptor hypofunction is hypothesized in schizophrenia, and antagonism could potentially worsen psychotic symptoms. *GABA receptor antagonism* - **GABA receptor antagonists** (e.g., flumazenil) block the effects of inhibitory neurotransmitter GABA and can cause seizures and increased anxiety, which would be detrimental in a patient with psychosis and anxiety. - Medications that *enhance* GABAergic transmission (e.g., benzodiazepines) are sometimes used to treat acute akathisia or anxiety, but long-term antagonism would be contra-indicated.

Question 235: A 23-year-old man presents to the emergency department with shortness of breath. The patient was at a lunch hosted by his employer. He started to feel his symptoms begin when he started playing football outside with a few of the other employees. The patient has a past medical history of atopic dermatitis and asthma. His temperature is 98.3°F (36.8°C), blood pressure is 87/58 mmHg, pulse is 150/min, respirations are 22/min, and oxygen saturation is 85% on room air. Which of the following is the best next step in management?

A. Albuterol and prednisone
B. IV epinephrine
C. IV fluids and 100% oxygen
D. Albuterol and norepinephrine
E. IM epinephrine (Correct Answer)

Explanation: ***IM epinephrine*** - The patient presents with **signs of anaphylaxis**, including acute onset shortness of breath, hypotension (BP 87/58 mmHg), tachycardia (HR 150/min), and hypoxia (SpO2 85%). Given his history of atopic dermatitis and asthma, he is at high risk for severe allergic reactions. - **Intramuscular epinephrine** is the first-line treatment for anaphylaxis as it acts rapidly to constrict blood vessels, relax airway smooth muscle, and reduce swelling, addressing both cardiovascular collapse and respiratory distress. *Albuterol and prednisone* - While **albuterol** (a bronchodilator) might help with bronchoconstriction, and **prednisone** (a corticosteroid) can reduce inflammation, these are not the immediate priority for severe anaphylaxis. - They act too slowly to counteract the rapid, systemic effects of anaphylaxis, particularly the life-threatening hypotension and airway compromise. *IV epinephrine* - **Intravenous epinephrine** is reserved for severe, refractory cases of anaphylaxis, or for patients already receiving IV infusions in a critical care setting. - Administering IV epinephrine requires careful titration due to the risk of arrhythmias and hypertension, and IM administration is preferred as the initial rapid response. *IV fluids and 100% oxygen* - **IV fluids** are crucial to address the distributive shock and hypotension in anaphylaxis, and **100% oxygen** is essential for hypoxia, but these are supportive measures. - They do not address the underlying immunological mechanism driving the severe allergic reaction as directly and effectively as epinephrine. *Albuterol and norepinephrine* - **Albuterol** can help with bronchospasm, but it is insufficient for systemic anaphylaxis. **Norepinephrine** is a potent vasopressor used for severe shock. - While norepinephrine can raise blood pressure, it does not have the broader beneficial effects of epinephrine on mast cell degranulation, airway dilation, and stabilization of vascular permeability, making it a secondary agent.

Question 236: A 65-year-old patient with a history of COPD and open-angle glaucoma in the left eye has had uncontrolled intraocular pressure (IOP) for the last few months. She is currently using latanoprost eye drops. Her ophthalmologist adds another eye drop to her regimen to further decrease her IOP. A week later, the patient returns because of persistent dim vision. On exam, she has a small fixed pupil in her left eye as well as a visual acuity of 20/40 in her left eye compared to 20/20 in her right eye. Which of the following is the mechanism of action of the medication most likely prescribed in this case?

A. Increasing the permeability of sclera to aqueous humor
B. Inhibiting the production of aqueous humor by the ciliary epithelium
C. Closing the trabecular mesh by relaxing the ciliary muscles
D. Opening the canal of Schlemm by contracting the ciliary muscle (Correct Answer)
E. Increasing reabsorption of aqueous humor by the ciliary epithelium

Explanation: **Correct Answer: Opening the canal of Schlemm by contracting the ciliary muscle** - The clinical presentation of a **small fixed pupil (miosis)** and **dim vision** strongly suggests the patient was prescribed a **cholinergic agonist** (e.g., pilocarpine), which acts by stimulating muscarinic M3 receptors. - Cholinergic agonists cause **ciliary muscle contraction**, which pulls on the scleral spur, widening the **trabecular meshwork** spaces and increasing outflow of aqueous humor through the **canal of Schlemm**, thereby lowering IOP. - The **miosis** (pupillary constriction) and **accommodative spasm** causing dim vision are characteristic side effects of muscarinic agonists. *Incorrect: Increasing the permeability of sclera to aqueous humor* - This mechanism does not correspond to any commonly prescribed **glaucoma medication** and is not a primary mechanism for IOP regulation. - The sclera serves as an anatomical boundary, not a primary site of aqueous humor outflow regulation. *Incorrect: Inhibiting the production of aqueous humor by the ciliary epithelium* - **Beta-blockers** (e.g., timolol) and **carbonic anhydrase inhibitors** (e.g., dorzolamide, acetazolamide) work by decreasing aqueous humor production. - These medications do **not** cause **miosis** (pupil constriction) or the dim vision seen in this patient, which are hallmark side effects of cholinergic agonists. *Incorrect: Closing the trabecular mesh by relaxing the ciliary muscles* - Relaxation of the ciliary muscles would **narrow the trabecular meshwork**, which would **decrease aqueous humor outflow** and **increase** IOP, contradicting the goal of glaucoma treatment. - This mechanism would not explain the **small fixed pupil** seen in this patient. *Incorrect: Increasing reabsorption of aqueous humor by the ciliary epithelium* - The **ciliary epithelium** is primarily responsible for the **production** of aqueous humor via active secretion, not its reabsorption. - Aqueous humor is removed through the **trabecular meshwork** (conventional outflow) and the **uveoscleral pathway** (unconventional outflow), not by ciliary epithelial reabsorption.

Question 237: A 5-year-old boy is brought to the emergency department by his parents for difficulty breathing. He was playing outside in the snow and had progressive onset of wheezing and gasping. His history is notable for eczema and nut allergies. The patient has respirations of 22/min and is leaning forward with his hands on his legs as he is seated on the table. Physical examination is notable for inspiratory and expiratory wheezes on exam. A nebulized medication is started and begins to relieve his breathing difficulties. Which of the following is increased in this patient as a result of this medication?

A. Cyclic GMP
B. Diacylglycerol
C. ATP
D. Protein kinase C
E. Cyclic AMP (Correct Answer)

Explanation: ***Correct: Cyclic AMP*** - The patient presents with an acute asthma exacerbation, likely triggered by cold weather and his atopic history (eczema, nut allergies). The nebulized medication is most likely a **beta-2 agonist** (e.g., albuterol), which acts by stimulating **adenylate cyclase**. - This stimulation leads to an increase in intracellular **cyclic AMP (cAMP)**, which activates protein kinase A (PKA). PKA then phosphorylates various targets, leading to **bronchodilation** by relaxing airway smooth muscle. *Incorrect: Cyclic GMP* - **Cyclic GMP (cGMP)** is primarily involved in smooth muscle relaxation via nitric oxide signaling, not typically the target of bronchodilators used for acute asthma exacerbations. - While some drugs like **nitrates** increase cGMP, bronchodilators like albuterol do not act through this pathway. *Incorrect: Diacylglycerol* - **Diacylglycerol (DAG)** is a secondary messenger produced by the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C. - It is involved in various cell signaling pathways, including the activation of **protein kinase C (PKC)**, but it is not directly increased by beta-2 agonists. *Incorrect: Protein kinase C* - **Protein kinase C (PKC)** is a family of enzymes activated by calcium and **diacylglycerol (DAG)**, playing roles in cell growth, differentiation, and metabolism. - Beta-2 agonists do not directly increase PKC activity; rather, they activate the adenylyl cyclase-cAMP-PKA pathway. *Incorrect: ATP* - **ATP (adenosine triphosphate)** is the cellular energy currency and is not specifically increased by beta-2 agonist therapy. - While ATP is the substrate for adenylate cyclase to produce cAMP, beta-2 agonists do not increase ATP levels themselves.

Question 238: A 32-year-old homeless woman is brought to the emergency department by ambulance 30 minutes after the police found her on the sidewalk. On arrival, she is unresponsive. Her pulse is 76/min, respirations are 6/min, and blood pressure is 110/78 mm Hg. Examination shows cool, dry skin. The pupils are pinpoint and react sluggishly to light. Intravenous administration of a drug is initiated. Two minutes after treatment is started, the patient regains consciousness and her respirations increase to 12/min. The drug that was administered has the strongest effect on which of the following receptors?

A. Ryanodine receptor
B. 5-HT2A receptor
C. M1 receptor
D. GABAA receptor
E. μ-receptor (Correct Answer)

Explanation: ***μ-receptor*** - The patient's presentation with **unresponsiveness, pinpoint pupils, and respiratory depression** is classic for an **opioid overdose**. - The rapid reversal of symptoms after drug administration indicates that the drug was an **opioid antagonist** like **naloxone**, which primarily acts on **μ-opioid receptors**. *Ryanodine receptor* - These receptors are primarily involved in **calcium release** from the sarcoplasmic reticulum in muscle cells, crucial for muscle contraction. - They are targeted by drugs used in conditions like **malignant hyperthermia**, which is not indicated here. *5-HT2A receptor* - This receptor is a subtype of **serotonin receptors** and is a target for **antipsychotics** and some **hallucinogens**. - While serotonin syndrome can cause altered mental status, it typically presents with **hyperthermia, myoclonus, and hypertension**, which are not seen in this patient. *M1 receptor* - These are **muscarinic acetylcholine receptors** found in the central nervous system and autonomic ganglia. - Drugs acting on M1 receptors are involved in conditions like **Alzheimer's disease** (cholinesterase inhibitors) or **motion sickness** (anticholinergics), and are not relevant to opioid overdose. *GABAA receptor* - This receptor is the primary target for **benzodiazepines** and **barbiturates**, which cause central nervous system depression. - While these drugs can cause respiratory depression and unresponsiveness, they typically do not cause **pinpoint pupils**, a hallmark of opioid overdose.

Question 239: A 56-year-old man is brought to the emergency department by his neighbor 2 hours after ingesting an unknown substance in a suicide attempt. He is confused and unable to provide further history. His temperature is 39.1°C (102.3°F), pulse is 124/min, respiratory rate is 12/min, and blood pressure is 150/92 mm Hg. His skin is dry. Pupils are 12 mm and minimally reactive. An ECG shows no abnormalities. Which of the following is the most appropriate treatment for this patient's condition?

A. Physostigmine (Correct Answer)
B. N-acetylcysteine
C. Flumazenil
D. Glucagon
E. Sodium bicarbonate

Explanation: ***Physostigmine*** - This patient presents with symptoms of **anticholinergic toxicity**, including confusion, fever (hyperthermia), tachycardia, hypertension, dry skin, and very dilated (mydriatic) pupils. - **Physostigmine** is a reversible acetylcholinesterase inhibitor that increases acetylcholine levels in the synapse, directly antagonizing the effects of anticholinergic agents, making it an appropriate treatment. *N-acetylcysteine* - **N-acetylcysteine** is the antidote for **acetaminophen overdose**, preventing liver damage. - This patient's symptoms are not consistent with acetaminophen toxicity, and there is no indication of acetaminophen overdose. *Flumazenil* - **Flumazenil** is used to reverse the effects of **benzodiazepine overdose**. - Benzodiazepine overdose typically causes central nervous system depression (sedation, respiratory depression), which is different from the anticholinergic toxidrome presented. *Glucagon* - **Glucagon** is primarily used in the treatment of severe **hypoglycemia** or **beta-blocker overdose**. - The patient's symptoms do not align with hypoglycemia or beta-blocker toxicity. *Sodium bicarbonate* - **Sodium bicarbonate** is commonly used to treat metabolic acidosis, especially in cases of **tricyclic antidepressant (TCA) overdose** to narrow the QRS complex and prevent arrhythmias. - While TCAs have anticholinergic properties, the primary indication for sodium bicarbonate is for cardiac toxicity on ECG (e.g., widened QRS), which is absent in this patient, and physostigmine is a more direct antidote for the anticholinergic syndrome itself.

Question 240: A 31-year-old male presents to the emergency room following an altercation with patrons at a local grocery store. He is acting aggressively toward hospital staff and appears to be speaking to non-existent individuals. On examination he is tachycardic and diaphoretic. Horizontal and vertical nystagmus is noted. The patient eventually admits to taking an illegal substance earlier in the evening. Which of the following mechanisms of action is most consistent with the substance this patient took?

A. Mu receptor agonist
B. GABA agonist
C. Biogenic amine reuptake inhibitor
D. NMDA receptor antagonist (Correct Answer)
E. Adenosine antagonist

Explanation: ***NMDA receptor antagonist*** - The patient's presentation with **aggressiveness**, **psychosis** (speaking to non-existent individuals), **tachycardia**, **diaphoresis**, and particularly **horizontal and vertical nystagmus**, is highly consistent with **phencyclidine (PCP) intoxication**. - PCP primarily acts as an **NMDA receptor antagonist**, blocking the activity of glutamate, which leads to its dissociative and psychotomimetic effects. *Mu receptor agonist* - **Mu receptor agonists** (e.g., opioids like heroin, morphine) typically cause central nervous system **depression**, miosis (pinpoint pupils), respiratory depression, and euphoria. - The patient's **aggressiveness**, nystagmus, and tachycardia are **not characteristic of opioid intoxication**. *GABA agonist* - **GABA agonists** (e.g., benzodiazepines, barbiturates, alcohol) typically cause central nervous system **depression**, sedation, anxiolysis, and ataxia, and can lead to respiratory depression in overdose. - The patient's agitation, psychosis, and nystagmus (especially vertical) are **not typical effects of GABAergic drugs**. *Biogenic amine reuptake inhibitor* - **Biogenic amine reuptake inhibitors** (e.g., cocaine, amphetamines) increase levels of neurotransmitters like dopamine, norepinephrine, and serotonin, leading to stimulant effects such as euphoria, agitation, paranoia, tachycardia, and hypertension. - While some symptoms like tachycardia and agitation are consistent, the prominent **vertical nystagmus** and dissociative psychosis are generally **not hallmarks of stimulant intoxication**. *Adenosine antagonist* - **Adenosine antagonists** (e.g., caffeine) cause central nervous system stimulation, leading to increased alertness, restlessness, and mild tachycardia. - The severe psychomotor agitation, prominent psychosis, and nystagmus seen in this patient are **far beyond the effects of typical adenosine antagonists**.

Question 241: A 23-year old man is brought to the emergency department by his brother after trying to jump out of a moving car. He says that the Federal Bureau of Investigation has been following him for the last 7 months. He recently quit his job at a local consulting firm to work on his mission to rid the world from evil. He does not smoke, drink alcoholic beverages, or use illicit drugs. He takes no medications. His temperature is 36.7°C (98.1°F), pulse is 90/min, respirations are 20/min, and blood pressure is 120/86 mm Hg. On mental status examination, his response to the first question lasted 5 minutes without interruption. He switched topics a number of times and his speech was pressured. He spoke excessively about his plan to “bring absolute justice to the world”. He has a labile affect. There is no evidence of suicidal ideation. A toxicology screen is negative. He is admitted to the hospital for his symptoms and starts therapy. One week later, he develops difficulty walking and a tremor that improves with activity. Which of the following is the most likely cause of this patient's latest symptoms?

A. Selective serotonin reuptake inhibitor
B. Serotonin–norepinephrine reuptake inhibitor
C. Dopamine antagonist (Correct Answer)
D. Histamine antagonist
E. Acetylcholine antagonist

Explanation: ***Dopamine antagonist*** - The patient's initial symptoms (delusions, pressured speech, grandiosity, labile affect) are consistent with **mania or psychosis**. Starting therapy for such conditions frequently involves **dopamine antagonists (antipsychotics)**. - The later development of difficulty walking and a tremor that improves with activity suggests **extrapyramidal symptoms (EPS)**, such as **drug-induced parkinsonism**, which is a common side effect of dopamine antagonists due to their blockade of D2 receptors in the nigrostriatal pathway. *Selective serotonin reuptake inhibitor* - While SSRIs can cause side effects like **akathisia** or **serotonin syndrome**, they are not typically associated with the tremor and gait difficulties described as improving with activity (parkinsonism-like symptoms). - SSRIs are primarily used for **depression and anxiety disorders**, and while sometimes used as adjunctive therapy in bipolar disorder, they are not first-line for acute mania/psychosis and are unlikely to cause these specific motor symptoms a week into treatment. *Serotonin–norepinephrine reuptake inhibitor* - SNRIs, similar to SSRIs, are used for **depression and anxiety**, and their side effect profile does not typically include **drug-induced parkinsonism** or gait disturbances that improve with activity. - The primary mechanism of action and common side effects of SNRIs do not align with the neurological symptoms of **tremor and difficulty walking** as described. *Histamine antagonist* - Histamine antagonists (like H1 blockers) are often used for **allergies or insomnia** and are not primary treatments for psychosis or mania. - While some may cause **sedation or anticholinergic effects**, they do not typically cause the specific motor symptoms of **tremor and gait abnormalities** that improve with activity, consistent with drug-induced parkinsonism. *Acetylcholine antagonist* - Acetylcholine antagonists (anticholinergics) are sometimes used to **treat EPS** caused by dopamine antagonists, rather than being the direct cause of these symptoms themselves. - While they can cause side effects like **dry mouth, blurred vision, or cognitive impairment**, they do not induce the characteristic tremor and gait issues that improve with activity as described.

Question 242: A 19-year-old woman, accompanied by her parents, presents after a one-week history of abnormal behavior, delusions, and unusual aggression. She denies fever, seizures or illicit drug use. Family history is negative for psychiatric illnesses. She was started on risperidone and sent home with her parents. Three days later, she is brought to the emergency department with fever and confusion. She is not verbally responsive. At the hospital, her temperature is 39.8°C (103.6°F), the blood pressure is 100/60 mm Hg, the pulse rate is 102/min, and the respiratory rate is 16/min. She is extremely diaphoretic and appears stiff. She has spontaneous eye-opening but she is not verbally responsive and she is not following commands. Laboratory studies show: Sodium 142 mmol/L Potassium 5.0 mmol/L Creatinine 1.8 mg/dl Calcium 10.4 mg/dl Creatine kinase 9800 U/L White blood cells 14,500/mm3 Hemoglobin 12.9 g/dl Platelets 175,000/mm3 Urinalysis shows protein 1+, hemoglobin 3+ with occasional leukocytes and no red blood casts. What is the best first step in the management of this condition?

A. Paracetamol
B. Dantrolene
C. Intravenous hydration
D. Switch risperidone to clozapine
E. Stop risperidone (Correct Answer)

Explanation: ***Stop risperidone*** - The patient's presentation with **fever, altered mental status, muscle rigidity**, and elevated **creatine kinase** after starting risperidone is highly suggestive of **neuroleptic malignant syndrome (NMS)**. - The **first and most critical step** in managing NMS is to **immediately discontinue the offending antipsychotic medication**, as continuation can worsen the severe symptoms and increase mortality. *Paracetamol* - While the patient has a high fever (39.8°C), **paracetamol** (acetaminophen) alone is **insufficient** to address the underlying severe hyperthermia and other systemic effects of NMS. - The fever in NMS is due to **muscle rigidity** and **dysregulation of the hypothalamic thermoregulatory center**, which requires more comprehensive management than antipyretics. *Dantrolene* - **Dantrolene** is a **muscle relaxant** often used in NMS to reduce muscle rigidity and hyperthermia by inhibiting calcium release from the sarcoplasmic reticulum. - However, the **withdrawal of the causative agent** (risperidone) is always the **initial and most crucial management step** before or in conjunction with supportive medications like dantrolene or bromocriptine. *Intravenous hydration* - **Intravenous hydration** is an important **supportive measure** in NMS to manage dehydration, support renal function (due to potential **rhabdomyolysis** from elevated CK), and help with temperature regulation. - While critical, it is **not the *first* step**; discontinuing the causative drug is paramount. *Switch risperidone to clozapine* - Switching to another antipsychotic, even clozapine, is **inappropriate** at this stage because the patient is experiencing a severe adverse reaction to an antipsychotic. - Reintroducing another antipsychotic could **exacerbate NMS** or trigger a similar reaction, and the immediate priority is to stabilize the patient by removing the trigger.

Question 243: A 76-year-old African American man presents to his primary care provider complaining of urinary frequency. He wakes up 3-4 times per night to urinate while he previously only had to wake up once per night. He also complains of post-void dribbling and difficulty initiating a stream of urine. He denies any difficulty maintaining an erection. His past medical history is notable for non-alcoholic fatty liver disease, hypertension, hyperlipidemia, and gout. He takes aspirin, atorvastatin, enalapril, and allopurinol. His family history is notable for prostate cancer in his father and lung cancer in his mother. He has a 15-pack-year smoking history and drinks alcohol socially. On digital rectal exam, his prostate is enlarged, smooth, and non-tender. Which of the following medications is indicated in this patient?

A. Hydrochlorothiazide
B. Midodrine
C. Oxybutynin
D. Tamsulosin (Correct Answer)
E. Clonidine

Explanation: **Tamsulosin** - This patient presents with symptoms of **benign prostatic hyperplasia (BPH)**, including urinary frequency, nocturia, post-void dribbling, and difficulty initiating micturition. A **smooth, enlarged, non-tender prostate** on DRE supports this diagnosis. - Tamsulosin is an **alpha-1 adrenergic receptor blocker** that relaxes the smooth muscle in the prostate and bladder neck, improving urine flow and relieving obstructive symptoms of BPH. *Hydrochlorothiazide* - This is a **thiazide diuretic** primarily used to treat hypertension and edema. - It would likely **worsen his urinary frequency** due to increased urine production, rather than improving his BPH symptoms. *Midodrine* - Midodrine is an **alpha-1 adrenergic agonist** used to treat orthostatic hypotension. - It would cause **vasoconstriction** and potentially worsen urinary retention by increasing smooth muscle tone in the bladder neck and prostate. *Oxybutynin* - Oxybutynin is an **anticholinergic agent** used to treat overactive bladder symptoms such as urgency and frequency. - While the patient has frequency, his primary issue is **obstructive BPH symptoms** (difficulty initiating stream, post-void dribbling), and oxybutynin could worsen urinary retention in this setting. *Clonidine* - Clonidine is an **alpha-2 adrenergic agonist** used primarily for hypertension and ADHD. - It works by reducing sympathetic outflow and would **not directly address the obstructive symptoms** of BPH.

Question 244: A 1-year-old boy presents to the emergency department with weakness and a change in his behavior. His parents state that they first noticed the change in his behavior this morning and it has been getting worse. They noticed the patient was initially weak in his upper body and arms, but now he won’t move his legs with as much strength or vigor as he used to. Physical exam is notable for bilateral ptosis with a sluggish pupillary response, a very weak sucking and gag reflex, and shallow respirations. The patient is currently drooling and his diaper is dry. The parents state he has not had a bowel movement in over 1 day. Which of the following is the pathophysiology of this patient’s condition?

A. Lower motor neuron destruction in the anterior horn
B. Antibodies against postsynaptic nicotinic cholinergic ion channels
C. Blockade of presynaptic acetylcholine release at the neuromuscular junction (Correct Answer)
D. Autoantibodies against the presynaptic voltage-gated calcium channels
E. Autoimmune demyelination of peripheral nerves

Explanation: ***Blockade of presynaptic acetylcholine release at the neuromuscular junction*** - The patient's symptoms, including **descending flaccid paralysis** (starting in the upper body and progressing downwards), **ptosis**, **sluggish pupillary response**, **weak suck/gag reflex**, **shallow respirations**, **drooling**, and **constipation**, are classic for **infant botulism**. - **Infant botulism** is caused by the **botulinum toxin** produced by *Clostridium botulinum*, which **inhibits acetylcholine exocytosis** at the neuromuscular junction. *Lower motor neuron destruction in the anterior horn* - This describes conditions like **poliomyelitis**, which causes **asymmetric flaccid paralysis** and spares extraocular and bulbar muscles. - The patient's presentation of **symmetric, descending paralysis** with prominent **bulbar involvement** (ptosis, weak suck/gag, sluggish pupils) is inconsistent with anterior horn cell destruction. *Antibodies against postsynaptic nicotinic cholinergic ion channels* - This is the pathophysiology of **myasthenia gravis**, which causes fluctuating muscle weakness that **worsens with activity** and improves with rest. - While it can cause ptosis and bulbar weakness, it typically does not present with the rapid, progressive descending paralysis, absent gag reflex, or pupillary sluggishness seen in this infant. *Autoantibodies against the presynaptic voltage-gated calcium channels* - This is characteristic of **Lambert-Eaton Myasthenic Syndrome (LEMS)**, which causes proximal muscle weakness and often improves with repeated muscle activation (unlike myasthenia gravis). - LEMS is rare in infants and typically associated with malignancy in adults; the patient's symptoms are more consistent with a neurotoxin. *Autoimmune demyelination of peripheral nerves* - This is the hallmark of **Guillain-Barré Syndrome (GBS)**, which typically presents with **ascending paralysis** (weakness starting in the legs and moving upwards) and **areflexia**. - The patient's **descending paralysis** and prominent **bulbar/autonomic symptoms** (pupil changes, constipation) are not typical for GBS.

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Acetylcholine receptors and function

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Cholinergic agonists (direct and indirect)

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Muscarinic antagonists

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Nicotinic antagonists

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Neuromuscular blocking agents

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Adrenergic receptor subtypes

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Alpha-adrenergic agonists

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Beta-adrenergic agonists

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Alpha-adrenergic antagonists

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Beta-adrenergic antagonists

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Sympathomimetics

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Autonomic drug interactions

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Clinical applications in autonomic disorders

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Cholinergic/Adrenergic drugs — MCQs

Cholinergic/Adrenergic drugs — MCQs

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