Forbes 1990.

Methods	Multicentre, randomised, double‐blind, placebo‐controlled, parallel‐group study, with a single oral dose administered at the onset of steady moderate or severe pain Duration: 6 h, with assessments at baseline, 1, 2, 3, 4, 5, and 6 h post dose
Participants	Dental surgery: third molar removal Patients were ≥ 15 years of age N = 401 (350 for efficacy) M 147, F 203 Mean age 21 years
Interventions	Aspirin 650 mg + caffeine 65 mg, n = 66 for efficacy Aspirin 650 mg, n = 68 for efficacy Aspirin 1000 mg, n = 71 for efficacy Caffeine 65 mg, n = 70 for efficacy Placebo, n = 75 for efficacy
Outcomes	PI: standard 4‐point scale PR: standard 5‐point scale PGE: standard 5‐point scale Withdrawals and dropouts Serious adverse events
Notes	Oxford Quality Score: R2, DB2, W1. Total = 5/5
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomisation schedule
Allocation concealment (selection bias)	Unclear risk	Method not described
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"all tablets were identical in appearance"
Size	Unclear risk	50 to 200 participants in relevant treatment arms