Factors moderating the relative effectiveness of varenicline and nicotine replacement therapy in clients using smoking cessation services

Aims To assess how far the greater effectiveness of varenicline over nicotine replacement therapy (NRT) is moderated by characteristics of the smokers or setting in clinical practice. Design We used observational data from 22,472 treatment episodes between 2013 and 2016 from smoking cessation services in England to assess whether differences between varenicline and NRT were moderated by a set of smoker and setting characteristics: these included level of social deprivation, age, gender, ethnic group, nicotine dependence, and treatment context. From the above, 15,640 episodes were analysed in relation to 4-week quit and 14,273 episodes at 12 weeks. All two-way interactions involving pharmacotherapy were fitted in addition to the main effects and a parsimonious model identified using a backwards stepwise selection procedure. Findings At both follow-up points, varenicline was associated with higher success rates overall (p<0.001 at both 4 and 12 weeks; adjusted odds ratio varenicline vs NRT = 1.82 [95%CI 1.61, 2.06] and 2.58 [95%CI 2.26, 2.94] at 4 and 12 weeks respectively). At 12 weeks, the relative benefits of varenicline were found to be influenced by the setting in which advice was provided (p