Repeated USMLE Questions Step 1 | Review- 67

Q- Ingestion of mushroom containing pilocarpine may cause which one of the following side effects?

A- Bronchodilation

B- Diarrhea

C- Hypertension

D- Tachycardia

B- Diarrhea- Some species of mushroom contains pilocarpine. It stimulates M receptors (parasympathomimetic effect) which cause diarrhea, bronchoconstriction, bradycardia and hypotension.

Q- In adrenergic synapses, increasing the concentration of norepinephrine leads to which one of the following?

A- Activation of dopa decarboxylase

B- Activation of presynaptic G coupled receptors

C- Increased release of norepinephrine

D- Stimulation of monoamine oxidase

B- Activation of presynaptic G coupled receptors- These receptors are considered autoregulatory to inhibit further neurotransmitter release and decreased synthesis of norepinephrine.

Q- Which one of the following is the mechanism of action of N-acetylcysteine in treating a case of acetaminophen toxicity?

A- Blocks metabolism of acetaminophen

B- Enhances clearance of acetaminophen

C- Induces P450 enzymes

D- Supplies sulfhydryl group to detoxify the drug metabolite

D- Supplies sulfhydryl group to detoxify the drug metabolite- Most acetaminophen is metabolized by glucuronidation into inactive metabolite. In high doses, cytochrome P450 may convert acetaminophen to reactive metabolite that may damage the liver. N-acetylcysteine supplies sulfhydryl groups to bind to this reactive metabolite and inactivate it.

Repeated USMLE Questions Step 1- Review- 67- Pharmacology

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