This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Pharmacology), Subject name: Pharmacology
Drug used for cigarette smoking cessation? 
Select and explain. 
A. Varenicline, B. Bupropion, C. Mecamylamine, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is 'd' i.e., All of the above Varenioline* It is a NR (Nicotine receptor) selective partial agonist and exerts rewarding action of nicotine through a4 b2 receptors.* This NN subtype nicotinic receptor partial agonist is under clinical trial for smoking cessation.Bupropion* This atypical antidepressants.* It inhibits DA and NA uptake.* It is metabolised to amphetamine like compound.* It is the only antidepressant which has excitatory action (all other have sedative action) can cause insomnia and can precipitate seizure.* It can be used in nicotine withdrawl for smoking cessation.Mecamylamine* It is nicotine ganglion blocker, blocks the reward effect of nicotine and abstinence.* Mecamylamine is used for smoking cessation.