Comparative effects of varenicline or combination nicotine replacement therapy versus patch monotherapy on candidate mediators of early abstinence in a smoking cessation attempt

Background and aims The phase-based model of smoking cessation treatment suggests that treatment needs may vary across phases (e.g. pre-cessation, cessation). This study tested the comparative effects of varenicline and combination nicotine replacement therapy (C-NRT) relative to nicotine patch monotherapy on pre-cessation and cessation phase candidate withdrawal, expectancy and motivation mediators; relations between mediators and abstinence; and indirect effects of enhanced treatments on abstinence via candidate mediators. Design Secondary mediation analysis of data from the open-label, randomized Wisconsin Smokers' Health Study 2, a comparative effectiveness trial of varenicline or C-NRT, versus patch monotherapy, in adults who smoked, recruited via media and community outreach. Setting Research clinics in Madison and Milwaukee, Wisconsin, USA. Participants A total of 1051 daily smokers motivated to quit smoking (52.5% female; mean age = 48.1, standard deviation = 11.6). Interventions Twelve weeks of varenicline (n = 407) or 12 weeks of combination nicotine patch and nicotine lozenge therapy (n = 421), both compared with 12 weeks of patch control condition (n = 230), with individual smoking cessation counseling. Measurements The primary abstinence outcome was biochemically verified 7-day point-prevalence abstinence 4 weeks post-target quit day (TQD). Candidate mediators (craving, positive smoking expectancies, withdrawal symptoms, and quitting motivation) were assessed via ecological momentary assessment from 1 week prior (pre-cessation phase) to 4 weeks after (cessation phase) the TQD. Findings Pre-cessation and cessation mean levels and slopes of craving [adjusted odds ratio (aOR) = 0.34-0.79], smoking expectancies (aOR = 0.46-0.79) and quitting motivation (aOR = 1.35-7.21) significantly predicted 4-week post-TQD abstinence (P < 0.05). Significant varenicline mediation occurred via greater suppression in pre-cessation craving [mediated effect (ab) = 0.09, standard error (SE) = 0.03, 95% confidence interval (CI) = 0.04-0.14] and smoking expectancies (ab = 0.06, SE = 0.02, 95% CI = 0.02-0.12). C-NRT mediation occurred via greater reduction in pre-post-TQD changes in craving (ab = 0.04, SE = 0.02, 95% CI = 0.01-0.08) and expectancies (ab = 0.03, SE = 0.02, 95% CI = 0.001-0.07), relative to patch monotherapy. Conclusion Among adult smokers seeking to quit, varenicline seems to work through its effects on suppression of craving and smoking expectancies pre-cessation while combination nicotine replacement therapy mediation seems to work through cessation-related reduction in craving and smoking expectancies changes.