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.