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?
Q242
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?
Q243
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?
Q244
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?
Q245
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?
Q246
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?
Q247
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?
Cholinergic/Adrenergic drugs US Medical PG Practice Questions and MCQs
Question 241: 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 242: 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 243: 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 244: 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 245: 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 246: 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 247: 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.
