Cytisine increases the chances of quitting, although absolute quit rates were modest in two recent trials. Varenicline at standard dose increased the chances of successful long-term smoking cessation between two- and threefold compared with pharmacologically unassisted quit attempts. Lower dose regimens also conferred benefits for cessation, while reducing the incidence of adverse events. More participants quit successfully with varenicline than with bupropion. Two open-label trials of varenicline versus NRT suggested a modest benefit of varenicline but confidence intervals did not rule out equivalence. Limited evidence suggests that varenicline may have a role to play in relapse prevention. The main adverse effect of varenicline is nausea, but mostly at mild to moderate levels and tending to subside over time. Possible links with serious adverse events, including serious psychiatric or cardiovascular events, cannot be ruled out.

Future trials of cytisine may test extended regimens and more intensive behavioural support. There is a need for further trials of the efficacy of varenicline treatment extended beyond 12 weeks.
Smoking cessation with varenicline, a selective alpha4beta2 nicotinic receptor partial agonist: results from a 7-week, randomized, placebo- and bupropion-controlled trial with 1-year follow-up.
Currently available smoking cessation therapies have limited success rates. Varenicline tartrate is a novel, selective nicotinic receptor partial agonist developed specifically for smoking cessation. This study evaluated the efficacy, tolerability, and safety of 3 varenicline doses for smoking cessation. Bupropion hydrochloride was included as an active control.
                A phase 2, multicenter, randomized, double-blind, placebo-controlled study of healthy smokers (18-65 years old). Subjects were randomized to varenicline tartrate, 0.3 mg once daily (n = 128), 1.0 mg once daily (n = 128), or 1.0 mg twice daily (n = 127), for 6 weeks plus placebo for 1 week; to 150-mg sustained-release bupropion hydrochloride twice daily (n = 128) for 7 weeks; or to placebo (n = 127) for 7 weeks.
                During the treatment phase, the continuous quit rates for any 4 weeks were significantly higher for varenicline tartrate, 1.0 mg twice daily (48.0%; P<.001) and 1.0 mg once daily (37.3%; P<.001), than for placebo (17.1%). The bupropion rate was 33.3% (P = .002 vs placebo). The carbon monoxide-confirmed continuous quit rates from week 4 to week 52 were significantly higher in the varenicline tartrate, 1.0 mg twice daily, group compared with the placebo group (14.4% vs 4.9%; P = .002). The bupropion rate was 6.3% (P = .60 vs placebo). Discontinuation owing to treatment-emergent adverse events was 15.9% for bupropion, 11.2% to 14.3% for varenicline, and 9.8% for placebo. No dose-related increases occurred in adverse events for varenicline.
                Varenicline tartrate demonstrated both short-term (1 mg twice daily and 1 mg once daily) and long-term efficacy (1 mg twice daily) vs placebo. Varenicline was well tolerated and may provide a novel therapy to aid smoking cessation.