NCT01162239.

Study characteristics
Methods	Country: USA Setting: outpatient medical care  Aim: to assess the efficacy of the relapse prevention treatment to other extended treatments, such as health education, brief contact, and varenicline Study design: open‐label parallel 4‐arm RCT
Participants	271 adult smokers, smoking 5+ CPD, who have all completed 12‐week course of varenicline + counselling 38.9% female, mean age 48.9.
Interventions	Extended brief contact Extended health education Extended relapse prevention ‐ varenicline Extended relapse prevention ‐ long‐term varenicline ‐ 12 weeks of varenicline treatment at standard dosage of 2 x 0.5 mg/day, plus ongoing access to varenicline for up to 40 additional weeks All participants in all trial arms receive 12 weeks of varenicline treatment at standard dosage of 2 x 0.5 mg/day
Outcomes	Primary: 7‐day PPA at weeks 12, 24, 52, 64, 104 Biochemically verified with exhaled CO at < 8 ppm  Secondary: comparison of combined extended vs brief treatment at weeks 24 and 52
Notes	New for 2022 update Funding by Pfizer (manufacturer‐funded study), and National Institute on Drug Abuse Author declaration of interests: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided on randomisation method (trial registry only)
Allocation concealment (selection bias)	Unclear risk	No information provided (trial registry only)
Blinding (performance bias and detection bias) All outcomes	High risk	Open‐label (and no placebo used in standard varenicline duration arm)
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up < 50% and similar between arms
Selective reporting (reporting bias)	Low risk	No evidence of selected reporting. All abstinence outcomes reported as planned