In the limited varenicline studies conducted to date, greater adherence predicts higher quit rates (Hays, Leischow, Lawrence, & Lee, 2010). In a pooled analysis of two RCTs, the effect of pharmacotherapy at 12 weeks was greater for those who had higher levels of adherence relative to each active drug treatment group as a whole for varenicline (quit selleck chemicals 17-AAG rates of 59% for participants with >80% adherence vs. 44% among those with <80% adherence) and bupropion (43% vs. 30%) (Hays et al., 2010). In the COMPASS smoking cessation intervention trial, good adherence to varenicline, defined as ��80% of days taken, was associated with doubling in Month 6 quit rates (52% vs. 25%) compared with poor adherence (Catz et al., 2011).

Similarly, in the parent trial to the current study, adherence was significantly associated with smoking abstinence such that participants who were quit at Month 3 had higher varenicline adherence rates than those who continued to smoke (Nollen et al., 2011). These differences in quit rates by adherence level suggest that adherence is an important factor in the effectiveness of smoking cessation pharmacotherapy. Adherence to smoking cessation pharmacotherapy has been associated with higher abstinence rates at end of treatment (bupropion and nicotine patch, Killen et al., 2004; nicotine lozenge, Shiffman, 2007; nicotine patch, Shiffman, Sweeney, Ferguson, Sembower, & Gitchell, 2008) and 52 weeks (bupropion and nicotine patch, Killen et al., 2006). Killen et al.

(2004) assessed pharmacotherapy adherence using self-reported patch use and urinalysis of bupropion metabolites; however, abstinence was associated with using more nicotine patches, and smoking reduction was associated with nicotine patch use and detectable levels of bupropion metabolites in this sample. Participants assigned to active nicotine patch and naltrexone who were adherent on purposeful nonadherence items (i.e., not intentionally stopping taking their medications) had higher abstinence rates at end of treatment than those who were nonadherent (61.36% vs. 49.12%, respectively; Toll, McKee, Martin, Jatlow, & O��Malley, 2007). Toll et al. also reported convergent validity for self-reported adherence with patch count, electronic drug exposure monitor cap data, and plasma naltrexone metabolite concentrations. Interventions to improve medication adherence may result in greater treatment effectiveness.

Two studies utilized the Medication Event Monitoring System (MEMS), an electronic pill bottle cap, and found that participants receiving weekly graphical feedback on their pill taking demonstrated greater adherence (Mooney, Sayre, Hokanson, Stotts, & Schmitz, 2007; Schmitz, Sayre, Stotts, Rothfleisch, & Mooney, 2005). Moreover, greater adherence to bupropion Brefeldin_A was associated with higher cessation rates (Mooney et al., 2007).