Two new studies of Chantix (varenicline)

Two new trials of the smoking cessation medicine varenicline (Chantix) were published this past weekend. One reported the results in 515 nicotine-dependent Japanese smokers (mainly men) and the other reported the results in 250 Korean and Taiwanese smokers.

The Japanese study compared the outcomes across various doses of varenicline, with participants taking the pills for 12 weeks, and then being followed up for a further 40 weeks off drug. As in previous studies, the 1mg dose (twice daily) achieved slightly higher quit rates than lower doses, albeit with higher reported side-effects. The 1mg dose achieved abstinence rates of 65% at 12 weeks, as compared with 40% among those using placebo pills. At one year follow up, 35% of those who were given 1mg pills for the first 12 weeks remained abstinent, compared with 23% of those who had taken placebo pills. So this study in Japan confirmed the safety and efficacy of Chantix, but the “effect size” – the degree to which the drug performed better than placebo, was not quite as impressive as previous studies. This was partly because a relatively large proportion of Japanese smokers in this study succeeded in quitting while using placebo pills.

Another study based in Korea and Taiwan directly compared 12 weeks of 1mg varenicline with 12 weeks of placebo in 250 smokers (mainly men). After 12 weeks, 60% of those using varenicline were not smoking, compared with 32% of those using placebo pills. After 24 weeks (i.e. another 12 weeks “off drug”) the quit rate was 47% among those who had used varenicline, versus 22% among those who had used placebo. As in previous studies, those taking varenicline were more likely to report some nausea, constipation and abnormal dreams, but these were generally mild in nature. Also like prior studies, those on Chantix were not less likely to report an increased appetite. This is noteworthy as most previous smoking cessation medicines (such as nicotine replacement therapy or bupropion) tend to reduce appetite compared with placebo, and suggests that Chantix works via a slightly different mechanism.

So far, the placebo-controlled trials of varenicline have been remarkably consistent in finding that it approximately doubles quit rates compared with placebo, and that this increased quit rate is maintained even after up to 40 weeks off drug. The early studies suggested that Chantix may result in higher quit rates than other pharmacological treatments for smoking. Whether this ultimately turns out to be the case will require additional studies directly comparing different treatments.

The take-home message for smokers interested in trying to quit is that this new medicine continues to demonstrate that it is safe and effective in increasing smokers’ chances of successfully quitting, with the most frequent side-effect being mild nausea (16-42% of users). The nausea is less marked at lower doses, and also appears less when taking the pill along with food and water. Most people using Chantix are able to continue using it and the initial nausea subsides. Those continuing to take Chantix for the full course (up to 24 weeks) tend to have higher quit rates than those discontinuing early.
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About the Author

MA, MAppSci, PhD

Dr. Jonathan Foulds is an expert in the field of tobacco addiction.