Perceived Treatment Assignment and Smoking Cessation in a Clinical Trial of Bupropion

Research on tobacco cessation pharmacotherapy often relies on double-blind, placebo-controlled randomized trials. These studies are designed to control for the placebo effect (i.e., the influence of participants' expectations on treatment outcome). Psychoactive effects of smoking cessation medications such as bupropion may allow participants to correctly guess their treatment assignment at rates greater than chance. Perceived treatment assignment could potentially impact smoking cessation rates. The aim of this study was to determine the impact of perceived treatment assignment on end-of-treatment cotinine-verified smoking abstinence among African-American light smokers [≤10 cigarettes per day (cpd)] enrolled in a double-blind, placebo-controlled study of bupropion. Participants were randomized to bupropion (150 mg bid) or placebo and received identical written materials and health education counseling. Participants (n = 390) included in this study reported their perceived treatment assignment on the end-of-treatment (week 7) survey. They were predominantly female (63.1%), 48.1 years (SD = 11.2), and smoked 8 cpd (SD = 2.5). The majority (81.3%) smoked menthol cigarettes. Participants given bupropion were more likely to correctly guess their treatment assignment (69%; 140/203) than those assigned to placebo (51.3%; 96/187). Quit rates by treatment assignment were 31.5% (bupropion) versus 13.9% (placebo) (OR = 2.78, 95% CI 1.61–5.43, P < 0.01). After adjusting for treatment, participants who perceived assignment to bupropion versus placebo were not more likely to be abstinent (OR = 1.37; 95% CI 0.71–2.64, P = 0.35).The interaction between treatment and perceived treatment assignment was also nonsignificant. Consistent with two previous studies with bupropion, there was evidence of blinding failure for the treatment group. However, in our study, perceived treatment assignment did not significantly impact cotinine-verified cessation outcome at end-of-treatment (week 7). These findings suggest that the role of perceived treatment assignment on smoking cessation with bupropion may differ for light smokers compared to heavier smokers (>10 cpd) sampled in the two earlier studies. Current findings might indicate that expectations of pharmacotherapy are less salient for light smokers.