Rico 2000.

Methods	Design: randomised, double blind, two‐way cross‐over Duration: 2 x 7 days with 3‐day washout Setting: not stated
Participants	Oncologic pain N = 44 30 women, 14 men Mean age 55 years Baseline pain > 6/10
Interventions	(1) codeine 120 mg daily to max 320 mg daily (average max dose 49 ± 15 mg x 4 daily) (2) tramadol 160 mg daily to max 400 mg daily (average max dose 68 ± 24 mg x 4 daily) All participants also received paracetamol 500 mg x 4 daily
Outcomes	PI: 10 cm VAS Patient preference Adverse events
Notes	Oxford Quality Score: R = 1, DB = 1, W = 1. Total = 3/5
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	Unclear risk	Method not clearly stated, used the same number of drops and both had bitter taste
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Method not clearly stated, used the same number of drops and both had bitter taste
Incomplete adverse event outcome data‐ patient level	Unclear risk	Denominator not clear
Selective reporting bias for adverse events	High risk	Selective reporting of a few AEs
Size	High risk	< 50 participants per treatment arm