Varenicline is prescribed as first-line pharmacotherapy for tobacco dependence. Its mechanism of action is best described as:

• A Irreversible antagonist at peripheral muscarinic receptors
• B Selective inhibitor of monoamine oxidase B
• C Full agonist at dopamine D2 receptors in the mesolimbic pathway
• D Partial agonist at alpha4beta2 nicotinic acetylcholine receptors ✓

Explanation

Varenicline is a partial agonist at the alpha4beta2 subtype of the nicotinic acetylcholine receptor. Partial agonism gives a dual effect: it stimulates the receptor enough to reduce craving and withdrawal symptoms when nicotine is absent, and it blocks full agonist activity of nicotine itself so smoking becomes less rewarding. Selegiline inhibits MAO-D, dopamine agonists are antiparkinsonian drugs, and muscarinic antagonists play no role in smoking cessation.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

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Written and medically reviewed by the StethoPrep medical team.