Do codeine and caffeine enhance the analgesic effect of aspirin?-A systematic overview

OBJECTIVE: To assess whether codeine and caffeine enhance the analgesic effect of aspirin in post-operative pain. METHOD: Systematic overview of the literature and meta-analysis of published randomized controlled trials (RCTs). RESULTS: Codeine 60 mg leads to a small increase in the analgesic effect of 650 mg of aspirin when total pain relief score (TOTPAR%) is used as a efficacy end-point. This increased effect was not seen when sum of pain intensity (SPID%) and proportions of patients responding with moderate to excellent pain relief were used as outcome measures. Caffeine did not enhance the analgesic effect of aspirin. CONCLUSION: Codeine 60 mg may produce a small increase in the analgesic effect of aspirin 650 mg. However, this effect is not clinically meaningful. Caffeine has no adjuvant analgesic effect. At over-the-counter (OTC) doses, caffeine and codeine are not useful in aspirin formulations.