Moore 1997.

Methods	Individual patient data meta‐analysis of trials of tramadol versus placebo, codeine and combination analgesics. All included trials were randomised, double blind, parallel group studies using a single oral doses. Medication administered when baseline pain reached a moderate to severe intensity Pain assessed at 0, 30, 60 mins, then hourly to 6 hours
Participants	A. Dental surgery, such as removal of impacted third molars (9 trials) N = 747 B. Various surgical procedures, such as abdominal, orthopaedic or gynaecological operations (9 trials) N = 558 M/F not reported Age not reported
Interventions	A. Codeine 60 mg, n = 374 Placebo, n = 373 B. Codeine 60 mg, n = 275 Placebo, n = 283
Outcomes	Number of participants with ≥50% pain relief over 6 h
Notes	Oxford Quality Score: R2, DB2, W1. Total = 5
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	"computerised random number generation"
Allocation concealment?	Unclear risk	Not described
Blinding? All outcomes	Low risk	identical or double dummy (from individual reports)