What is the action of varenicline in smoking cessation?

• A. Increases dopamine release causing euphoria
• B. Blocks nicotine binding and reduces reinforcement
• C. Inhibits acetylcholine receptors
• D. Acts as opioid agonist

Answer: (B)

Varenicline binds with high affinity to the alpha4beta2 nicotinic acetylcholine receptors in the brain and acts as a partial agonist. This dual action means it provides enough receptor stimulation to ease withdrawal and cravings, while also blocking nicotine from fully activating the receptor. As a result, nicotine’s typical dopamine surge in the reward pathways is blunted, reducing the reinforcement a smoker feels from smoking. This combination—partial activation plus competitive blockade—explains why varenicline helps people quit. It does not produce euphoria like nicotine, does not broadly inhibit acetylcholine receptors, and is not an opioid agonist.