Dhaliwal 1995.

Methods	Design: Randomised, double blind, two‐period cross‐over study Duration: 2 x 7 days
Participants	Chronic cancer pain N = 35 participants (30 completers: 13 women, 17 men) Mean age 64 years
Interventions	Controlled‐release codeine at 100, 150 or 200 mg 2‐hourly Placebo Rescue medication: paracetamol 300 mg plus codeine 30 mg once or twice every 4 hours
Outcomes	PI: 100 mm VAS and five‐point NRS (0‐4) Doses of rescue medication per day Pain disability index Withdrawals
Notes	Oxford Quality Score: R = 1, DB = 2, W = 1. Total = 4/5
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method used to generate sequence not clearly stated
Allocation concealment (selection bias)	Unclear risk	Method not clearly stated
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"matching placebos"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"matching placebos"
Incomplete adverse event outcome data‐ patient level	Low risk	> 90% of participants included
Selective reporting bias for adverse events	Low risk	All AEs included
Size	Unclear risk	< 50 participants per treatment arm