Nicotine receptor partial agonists effective for smoking cessation

Clinical question: 
How effective are nicotine receptor partial agonists for smoking cessation?
Bottom line: 
Varenicline at standard dosage (1.0mg twice a day) increased the chances of successful long-term smoking cessation by more than two-fold compared with pharmacologically unassisted quit attempts. Varenicline at reduced dosage appeared to reduce the impact of adverse events in the early weeks of treatment and remained an effective aid to smoking cessation, delivering success rates similar to those achieved with nicotine replacement therapy (NRT) and bupropion. Limited evidence suggests varenicline may have a role to play in relapse prevention. The main adverse effect of varenicline was nausea, but mostly at mild to moderate levels, and this tended to subside over time.
Caveat: 
Two open-label trials of varenicline versus NRT suggested a modest benefit for varenicline, but were inconclusive. Possible links with serious adverse events, including depressed mood, agitation and suicidal thoughts, have been reported but are so far not substantiated. Cytisine may also increase the chances of quitting, but the evidence at present is inconclusive.
Context: 
Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine, to counteract withdrawal symptoms (acting as an agonist), and reducing smoking satisfaction (acting as an antagonist).
Review CD#: 
CD006103
PEARLS No: 
305
Date: 
April, 2011
Authored by: 
Brian R McAvoy