Kristensen 2005.

Methods	Two‐group, open‐label randomised clinical trial. 25 unmarked closed envelopes with each study medication were placed in a hat and drawn by each participant following randomisation.
Participants	Geographic region: Norway. N = 50. Mean age: 36 years. 76% male. Inclusion criteria: ICD10 diagnosis of opioid dependence. Exclusion criteria: younger than 25 years.
Interventions	180 days of flexible dosing (methadone) and fixed dosing (buprenorphine). Buprenorphine (sublingual tablets) mean dose 16 mg per day. Methadone dose of 106 mg per day.
Outcomes	Retention in treatment, urinalysis.
Funding source	The study was funded by "Sosial‐og helsedepartementet".
Declarations of interest	Two authors supported to attend international congress by Schering‐Plough.
Notes	50 long term (> 10 years) opioid dependent participants.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomised. Unmarked, sealed envelopes participants drew from a hat.
Allocation concealment (selection bias)	Low risk	Unmarked, sealed envelopes.
Blinding (performance bias and detection bias) All outcomes	Low risk	Open‐label. Objective outcome measurement not influenced by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Intention‐to‐treat.