Immediate versus delayed quitting and rates of relapse among smokers treated successfully with varenicline, bupropion SR or placebo

AIMS We assessed to what degree smokers who fail to quit on the target quit date (TQD) or lapse following TQD eventually achieve success with continued treatment. DESIGN A secondary analysis of pooled data of successful quitters treated with varenicline (306 of 696), bupropion (199 of 671) and placebo (121 of 685) from two identically-designed clinical trials of varenicline versus bupropion sustained-release and placebo. SETTING Multiple research centers in the US. PARTICIPANTS Adult smokers (n==2052) randomized to 12 weeks drug treatment plus 40 weeks follow-up. MEASUREMENT The primary end-point for the trials was continuous abstinence for weeks 9-12. TQD was day 8. Two patterns of successful quitting were identified. Immediate quitters (IQs) were continuously abstinent for weeks 2-12. Delayed quitters (DQs) smoked during 1 or more weeks for weeks 2-8. FINDINGS Cumulative continuous abstinence (IQs + DQs) increased for all treatments during weeks 3-8. Overall IQs and DQs for varenicline were (24%; 20%) versus bupropion (18.0%, P=0.007; 11.6%, P<0.001) or placebo (10.2%, P<0.001; 7.5%, P<0.001). However, DQs as a proportion of successful quitters was similar for all treatments (varenicline 45%; bupropion 39%; placebo 42%) and accounted for approximately one-third of those remaining continuously abstinent for weeks 9-52. No gender differences were observed by quit pattern. Post-treatment relapse was similar across groups. CONCLUSIONS Our data support continuing cessation treatments without interruption for smokers motivated to remain in the quitting process despite lack of success early in the treatment.