Herrera 1995.

Study characteristics
Methods	Study design: parallel RCT Country: Venezuela Recruitment: community volunteers
Participants	322 smokers > 10 cigarettes per day, scoring ≥ 4 on FTND, no serious illness. Only those who were ready to quit after 4 weeks of behavioural treatment were randomised. 57% men, average age ~38, average cigarettes per day: 33 for high dependence, 16 for low dependence
Interventions	Low‐dependence smokers (FTND 4 ‐ 6): 1) 2 mg nicotine gum 2) Placebo gum High‐dependence smokers (FTND 7 ‐ 11): 1) 4 mg nicotine gum plus 2) 2 mg nicotine gum Participants also randomised to starting medication with increasing dose for 1 week before TQD, or to start at full dose on TQD ‐ there was no blinding for this
Outcomes	Sustained abstinence at 2 years (1 year also reported) Validation: expired CO < 6 ppm Adverse events: measured daily during treatment
Notes	Relapse between 1 and 2 years similar between low‐dependence groups. Higher relapse in 4 mg high‐dependence group than 2 mg Funding and conflicts of interest not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method not stated
Allocation concealment (selection bias)	Unclear risk	Stratified on dependency scores, to determine dosage. Then "randomly assigned"
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as double‐blind
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	68 participants dropped out in phase 1 (weeks 1 to 2) and 10 participants in phase 2 (weeks 4 to 6), i.e. before randomisation. Dropout rates not reported, but classified as relapsed "and not further analyzed"