Effect of varenicline on smoking cessation through smoking reduction: a randomized clinical trial.

IMPORTANCE Some cigarette smokers may not be ready to quit immediately but may be willing to reduce cigarette consumption with the goal of quitting. OBJECTIVE To determine the efficacy and safety of varenicline for increasing smoking abstinence rates through smoking reduction. DESIGN, SETTING, AND PARTICIPANTS Randomized, double-blind, placebo-controlled, multinational clinical trial with a 24-week treatment period and 28-week follow-up conducted between July 2011 and July 2013 at 61 centers in 10 countries. The 1510 participants were cigarette smokers who were not willing or able to quit smoking within the next month but willing to reduce smoking and make a quit attempt within the next 3 months. Participants were recruited through advertising. INTERVENTIONS Twenty-four weeks of varenicline titrated to 1 mg twice daily or placebo with a reduction target of 50% or more in number of cigarettes smoked by 4 weeks, 75% or more by 8 weeks, and a quit attempt by 12 weeks. MAIN OUTCOMES AND MEASURES Primary efficacy end point was carbon monoxide-confirmed self-reported abstinence during weeks 15 through 24. Secondary outcomes were carbon monoxide-confirmed self-reported abstinence for weeks 21 through 24 and weeks 21 through 52. RESULTS The varenicline group (n = 760) had significantly higher continuous abstinence rates during weeks 15 through 24 vs the placebo group (n = 750) (32.1% for the varenicline group vs 6.9% for the placebo group; risk difference (RD), 25.2% [95% CI, 21.4%-29.0%]; relative risk (RR), 4.6 [95% CI, 3.5-6.1]). The varenicline group had significantly higher continuous abstinence rates vs the placebo group during weeks 21 through 24 (37.8% for the varenicline group vs 12.5% for the placebo group; RD, 25.2% [95% CI, 21.1%-29.4%]; RR, 3.0 [95% CI, 2.4-3.7]) and weeks 21 through 52 (27.0% for the varenicline group vs 9.9% for the placebo group; RD, 17.1% [95% CI, 13.3%-20.9%]; RR, 2.7 [95% CI, 2.1-3.5]). Serious adverse events occurred in 3.7% of the varenicline group and 2.2% of the placebo group (P = .07). CONCLUSIONS AND RELEVANCE Among cigarette smokers not willing or able to quit within the next month but willing to reduce cigarette consumption and make a quit attempt at 3 months, use of varenicline for 24 weeks compared with placebo significantly increased smoking cessation rates at the end of treatment, and also at 1 year. Varenicline offers a treatment option for smokers whose needs are not addressed by clinical guidelines recommending abrupt smoking cessation. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01370356.