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. 2014 Dec 11;2014(12):CD009281. doi: 10.1002/14651858.CD009281.pub3

Diamond 2000.

Methods Multicentre, randomised, double‐blind, placebo‐controlled, parallel‐group study, with a single oral dose administered (baseline pain intensity not reported)
Duration: 6 h, with assessments at baseline, 15, 30, 45, 60, 90, and 120 minutes, then hourly through to 6 h post dose
Participants Acute tension‐type headache ‐ in accordance with IHS criteria, with 3 to 15 tension‐type headaches every month for ≥ 1 year, and ≥ 75% of headaches responsive to non‐prescription‐strength analgesics
Participants with occasional migraine headaches (< 2 per month) were not excluded provided they could differentiate the two types of headache
No alcohol, caffeine‐containing foods/beverages, or any other analgesic within 4 h before dosing
Participants at least 18 years of age
N = 331 (301 for efficacy)
M 57, F 244
Mean age 37 years
Interventions Ibuprofen 400 mg + caffeine 200 mg, n = 97 for efficacy
Ibuprofen 400 mg, n = 99 for efficacy
Caffeine 200 mg, n = 57 for efficacy
Placebo, n = 48 for efficacy
Outcomes PI: standard 4‐point scale
PR: standard 5‐point scale
PGE: standard 5‐point scale
Withdrawals and dropouts
Notes Oxford Quality Score: R1, DB1, W1. Total = 3/5
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Unclear risk Method used to generate random sequence not described
Allocation concealment (selection bias) Unclear risk Method not described
Blinding of participants and personnel (performance bias) 
 All outcomes Unclear risk Method not described
Size Unclear risk 50 to 200 participants in relevant treatment arms