Which statement best describes evidence-based pharmacotherapies for nicotine dependence and their mechanisms?

• A. Only nicotine replacement therapy is effective; bupropion and varenicline have no effect.
• B. Nicotine replacement therapy reduces withdrawal; bupropion reduces cravings; varenicline reduces cravings and withdrawal.
• C. Bupropion increases cravings; varenicline worsens withdrawal; nicotine replacement has no effect.
• D. Vaccination against nicotine is the primary strategy; NRT is ineffective.

Answer: (B)

Pharmacotherapies for nicotine dependence work by addressing withdrawal and cravings through distinct mechanisms. Nicotine replacement therapy provides nicotine in controlled amounts, which eases withdrawal and reduces cravings so the urge to smoke is less intense. Bupropion targets brain dopamine and norepinephrine systems, helping to lessen withdrawal symptoms and cravings without delivering nicotine directly. Varenicline acts as a partial agonist at the same nicotinic receptors nicotine binds to; this pharmacologic action both eases withdrawal and dampens the rewarding effects of smoking, leading to reduced cravings and withdrawal. This combination of effects matches the best-supported description: nicotine replacement lowers withdrawal, bupropion reduces cravings, and varenicline reduces both cravings and withdrawal. The other statements contradict well-established mechanisms and are not consistent with current evidence.