Gonzales 2001.

Methods	BUPROPION Randomized controlled trial Setting: 16 clinical trial centres, USA Recruitment: volunteers who had previously failed to quit using bupropion
Participants	450 smokers, >= 15 CPD, who had previously used bupropion for at least 2w without adverse effects; 55% F (Placebo), 48% F (Bup); av. age 45, av. CPD not specified, no details of depression history
Interventions	1. Bupropion 300 mg/day for 12w, begun 7 days pre‐TQD. 2. Placebo Both arms: brief individual counselling at visits w1‐7, 9, 12, + telephone counselling at 4 and 5m
Outcomes	Abstinence at 12m, prolonged from w4 Validation: CO <= 10 ppm at each visit
Notes	6m data published. 12m data presented in a poster used since 2003 update Funding: GlaxoWellcome Inc
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Participants who satisfied the inclusion criteria were randomized to the treatment phase and received either bupropion SR ... or matching placebo. Eligible participants were assigned a protocol‐specific treatment number on the basis of a randomization code provided by GlaxoWellcome."
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not described
Blinding (performance bias and detection bias) All outcomes	Low risk	"Even though participants and the site staff were blinded to the drug assignments and the site staff did not encourage participants to speculate on their assignments, the lower placebo abstinence rates in the current study may be attributable to the previous experiences of participants with bupropion in their previous cessation attempts." However, little difference in completion between two arms, suggesting blinding may have been successful.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Number of participants followed‐up at 12m unclear. "...all participants who stopped participating in the study during the treatment phase were considered to be smokers."