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?
Q132
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?
Q133
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?
Q134
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?
Q135
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?
Q136
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?
Q137
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?
Q138
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?
Q139
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?
Q140
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?
Cholinergic/Adrenergic drugs US Medical PG Practice Questions and MCQs
Question 131: 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 132: 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 133: 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 134: 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 135: 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 136: 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 137: 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 138: 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 139: 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 140: 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**.
