Cigarette smoking is the leading cause of premature death worldwide. Most smokers want to quit, but success rates at one year are extremely low. Adding medications to the smoking cessation plan increases the success rate; however, at one year, the abstinence rate is 7 to 30 percent. Varenicline (Chantix) is a new pharmacologic agent that specifically targets the nicotine receptor site that rewards smokers. Varenicline should reduce cravings and symptoms of withdrawal from nicotine. Nides and colleagues evaluated the effectiveness, tolerability, and safety of three varenicline dosages.

The randomized, double-blind, placebo-controlled study compared varenicline with bupropion (Wellbutrin) and placebo for smoking cessation. Participants were randomly selected to receive varenicline (0.3 mg once daily, 1.0 mg once daily, or 1.0 mg twice daily) for six weeks plus one week of placebo or extended-release bupropion (150 mg twice daily) or placebo for seven weeks. Inclusion criteria were smoking an average of at least 10 cigarettes per day during the previous year, no abstinence period of more than three months in the previous year, and good general health. During the study, participants were evaluated and given standardized smoking cessation counseling weekly. Effectiveness was determined using a smoking diary and breath carbon dioxide measurements. The measurements were repeated at weeks 12, 24, and 52. Adverse events were recorded during the seven-week trial period.

The study population consisted of 638 participants who were almost equally distributed among treatment groups. The mean average cigarette use was 20 cigarettes per day for 24 years. At week 4, those receiving 1.0 mg of varenicline twice daily had a 48.0 percent quit rate, and those receiving 1.0 mg once daily had a 37.3 percent quit rate, compared with a 17.1 percent quit rate for placebo. The bupropion quit rate was 33.3 percent. The quit rate for 1.0 mg of varenicline twice daily during the four- to 52-week follow-up period was 14.4 percent, which was significantly higher than the placebo rate. The bupropion group quit rate during that period was similar to placebo. The discontinuation rates for all treatments were similar. The most common adverse event in the varenicline group was nausea, which tended to occur in the first week and decrease over time.

The authors conclude that varenicline plus counseling is effective for short- and long-term smoking cessation. They add that the pharmacologic agent may assist persons in abstaining from cigarette smoking and reduce the risk of relapse.