Varenicline: new treatment with efficacy in smoking cessation

Smoking is a significant public health problem, and existing treatments have demonstrated only moderate efficacy in assisting smokers to quit. Varenicline, recently approved by the U.S. Food and Drug Administration and the European Agency for the Evaluation of Medicinal Products as an aid to smoking cessation treatment, has a novel mechanism of action, targeting the specific nicotinic acetylcholine receptor (nAChR) associated with nicotine-induced behaviors (alpha4beta2 nAChR). It has both agonistic and antagonistic properties that together are believed to account for reduction of craving and withdrawal as well as blocking the rewarding effects of smoking. The clinical efficacy and tolerability of varenicline has been demonstrated in phase III clinical trials involving more than 2,000 cigarette smokers. At the end of the treatment period in two 12-week, multicenter, randomized, double-blind, placebo-controlled studies, patients receiving varenicline (1 mg twice daily) experienced an increase in the odds of quitting smoking by nearly fourfold compared with those receiving placebo, and almost twofold compared with the odds for patients receiving 150 mg bupropion SR (sustained release) twice daily. In these two trials where patients were randomized to either varenicline or bupropion, the efficacy of varenicline was consistently superior at 12 weeks; this result sustained significance at 24 weeks in both studies and up to 52 weeks in one study. Nausea, a common adverse event reported in clinical trials, led to few treatment discontinuations. Its targeted mechanism of action, superior efficacy and excellent tolerability make varenicline a welcome and useful addition to the therapeutic options for smoking cessation.