Forbes 1991.

Methods	Multicentre, randomised, double‐blind, placebo‐controlled, parallel group study, with a single oral dose administered at the onset of moderate or severe pain Eight‐hour study period, with assessments at baseline, 0.5, one, two, three, four, five, six, seven, and eight hours post‐dose
Participants	Dental surgery ‐ third molar removal Caffeine‐containing foods and beverages were prohibited for four hours before taking study medication and for the following 8‐hour study period Patients were at least 15 years of age N = 362 (298 for efficacy) M: 121, F: 177 Mean age: 22 years
Interventions	Ibuprofen 100 mg + caffeine 100 mg, n = 49 for efficacy Ibuprofen 100 mg, n = 49 for efficacy Ibuprofen 200 mg + caffeine 100 mg, n = 44 for efficacy Ibuprofen 200 mg, n = 48 for efficacy Ibuprofen 50 mg, n = 57 for efficacy Placebo, n = 51 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: R1, DB2, W1. Total = 4
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Gives reference to methods in earlier reports that are low risk
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"identically appearing capsules"
Size	Low risk	< 50 participants in relevant treatment groups