Rationale: For the management of common disorders producing short-lasting pain, there is very good evidence of the efficacy of aspirin. Yet paracetamol is often preferred, despite that evidence of its efficacy is much less sound. The reason for this appears to be a concern over gastrointestinal (GI) toxicity. If this concern is misplaced, so may be the preference for paracetamol, with the consequence of widespread sub-optimal treatment. Our purpose in this analysis of pooled individual patient data from clinical studies of aspirin is to adduce the evidence that will show whether or not this is so, for the benefit of consumers and health-care professionals who advise them.
Methods: The frequencies of all and GI adverse events (AEs) and adverse drug reactions (ADRs) were calculated from the pooled individual patient data of nine similar randomized, double-blind, placebo controlled clinical trials of single-doses of aspirin 1000 mg in the treatment of acute migraine attacks, episodic tension-type headache and dental pain. Absolute differences between active and placebo AE and ADR rates, and numbers-needed-to-harm (NNH), were calculated.
Results: Of 2852 patients included in the analysis, 1581 were treated with aspirin and 1271 with placebo. Reported AE rates were 14.9% and 11.1% amongst patients allocated to aspirin and placebo respectively (NNH: 26), with the GI system most frequently affected (aspirin: 5.9%; placebo: 3.5%; NNH: 42). Reported ADR rates were much lower (aspirin: 6.3%; placebo: 3.9%; NNH: 42), especially for the GI system (aspirin: 3.1%; placebo: 2.0%; NNH: 91). Most of the AEs and ADRs were mild or moderate, and none was serious.
Conclusions: The GI ADR differences between aspirin and placebo are not great enough to support decision choices for short-lasting acute pain based on tolerability: these are better based on efficacy.