Comparison of the effectiveness of varenicline and combination nicotine replacement therapy for smoking cessation in clinical practice.

To compare the effectiveness of varenicline and combination nicotine replacement therapy (NRT) for treating smokers attempting to stop, as it is unclear which of the 2 is more effective. Data from 167,487 treatment episodes in patients from 42 National Health Service Stop Smoking Services (April 1, 2009, through June 30, 2011) using varenicline or combination NRT were analyzed. The outcome was carbon monoxide-validated 4-week smoking abstinence. Potential predictors were age, sex, occupational grade, exemption from prescription charges, intervention setting (specialist or other), support (group or other), and year of quit attempt. Observed smoking abstinence rates were higher with varenicline (43.5% vs 36.9%). However, there was evidence of systematic variation in medication effect across clinical services and differences in predictors of outcome between medications. Allowing for these influences indicated a small mean advantage for varenicline (odds ratio, 1.080; 95% CI, 1.003-1.163; difference, 1.86%; 95% CI, 0.07%-3.67%; P=.04). The relative effectiveness of the 2 medications was not moderated by setting, type of support, or year. The relative effect of medication varies substantially according to clinical practice and population treated. Averaged across current English clinical practice and populations, varenicline is marginally more effective than combination NRT. Demographic and intervention characteristics associated with success predict varenicline use.