Schnoll 2010.

Methods	Parallel randomised double‐blind placebo‐controlled trial Setting: academic centre, USA Recruitment: community volunteers Study period: October 2004 to March 2008
Participants	N = 575 44.7% females; average age: 44.8; average cigarettes/d: 21.2 Inclusion criteria: age 18 to 65 years, smoked ≥ 10 cigarettes/d for at least the past year Exclusion criteria: pregnancy or lactation, uncontrolled hypertension, unstable angina, heart attack or stroke within previous 6 months, recent diagnosis of cancer or kidney or liver failure, history of organ transplantation, current diabetes, drug or alcohol dependence, history of Axis I psychiatric disorder, current use of a concomitant medication, or current treatment of nicotine addiction
Interventions	Transdermal nicotine (21 mg) for 8 weeks and placebo for 16 weeks (standard therapy) (n = 287) vs transdermal nicotine (21 mg) for 24 weeks (extended therapy) (n = 288) Behavioural counseling was provided to both groups at weeks ‐2, 0, 1, 4, 8, 12, 16, and 20.
Outcomes	Primary outcome: self‐reported and biochemically confirmed 7‐day point prevalence abstinence at weeks 24 and 52 Secondary outcomes: self‐reported continuous abstinence; prolonged abstinence; time to relapse; incremental cost per additional quitter by treatment group at week 24 Also evaluated: side effects; adherence
Funding source	Transdisciplinary Tobacco Use Research Center Grant from the National Cancer Institute and the National Institute on Drug Abuse at the National Institutes of Health
Declaration of interest	Dr Lerman has served as a consultant to GlaxoSmithKline ‐ one company that manufactures the nicotine patch. She has also served as a consultant for or has received research funding from AstraZeneca, Pfizer, and Novartis. Financial support for this study was not provided by an industry sponsor. Dr Lerman had full access to the data and had full responsibility for the decision to submit for publication.
Notes	Analyses of pharmacogenetics are reported in Gold 2012 and Lerman 2010.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐based randomisation; non‐stratified randomisation scheme was generated by sampling without replacement and by using small blocks of 20 participants.
Allocation concealment (selection bias)	Low risk	A computer programme linked randomisation to the patch supply, and only the database manager could link identification to treatment allocation.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and all study personnel, except for the database manager, were blinded to randomisation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Participants and all study personnel, except for the database manager, were blinded to randomisation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Completion rates at 52 weeks: 83% for extended therapy; 79% for standard therapy
Selective reporting (reporting bias)	Low risk	Protocol available at ClinicalTrials.gov (registration number: NCT00364156); no deviations from prespecified outcomes identified
Other bias	Low risk	Analyses of pharmacogenetics were conducted only in Caucasians. Distribution seems balanced between treatment groups because of randomisation.