Varenicline reduces the effects of nicotine by blocking receptors.

• A. Increases receptor sensitivity
• B. Acts as a full agonist
• C. Has no effect
• D. Reduces effects of nicotine by blocking receptors

Answer: (D)

Varenicline works by binding to the brain’s nicotinic receptors, specifically the α4β2 subtype, and acting as a partial agonist. This means it provides some receptor activation to ease withdrawal, but it blocks nicotine from fully activating the receptor. By occupying the receptor, it reduces nicotine’s rewarding effects, which helps prevent urge to smoke.

The statement that varenicline reduces the effects of nicotine by blocking receptors best captures this mechanism. It’s not about increasing receptor sensitivity, and it’s not a full agonist—the drug does not produce nicotine-like full receptor activation. It does have some activity to lessen withdrawal, but its key clinical effect is blunting nicotine’s reinforcement through receptor occupancy.