Which of the following drug is used for smoking cessation?

DOC for smoking cessation : Varenicline Nicotine patch and gum are also used. Bupropion is also used in smoking cessation. Varenicline: is paial agonist at neuronal nicotinic acetylcholine receptor in CNS. Patient taking varenicline should be monitored for suicidal thoughts, vivid nightmares and mood changes. Acamprosate : agent used in alcohol dependent treatment programs with an as yet poorly understood mechanism of action. Gabapentin: analog of GABA: Does not act at GABA receptor. It's precise mechanism is not known. It is approved as adjunct therapy for focal seizure and treatment of post herpetic neuralgic. Nalmefene :- is opioid antagonist use for opioid poisoning