Ling 1998.

Methods	Four‐group, double‐blind, randomised multi‐site clinical trial using a random number table to pre‐label medications by pharmacy staff.
Participants	Geographic region: USA (12 sites). N = 736. Mean age: 36 years. 68% male. Inclusion criteria: DSM‐III diagnosis of opioid dependence, state or federal criteria for methadone maintenance treatment, daily use of opiates in past six months. Exclusion criteria: MMT in last 30 days, alcohol dependence, serious medical condition including AIDS, current use of neuroleptics, anticonvulsants or disulphiram, pregnancy.
Interventions	16 weeks of maintenance, fixed dosing. Buprenorphine (solution) 1 mg, 4 mg, 8 mg or 16 mg/day.
Outcomes	Retention in treatment, urinalysis for illicit opioids, craving, and global ratings by participants and staff.
Funding source	NIDA grants.
Declarations of interest	None reported.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Random numbers table".
Allocation concealment (selection bias)	Low risk	Pharmacy‐controlled randomisation. "assigning patients to the medication that had been labelled in a blinded fashion by the research pharmacy using a random numbers table".
Blinding (performance bias and detection bias) All outcomes	Low risk	Participants and staff at the sites were blind to medication and dose.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Intention‐to‐treat.