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Kurth T, Glynn RJ, Walker AM, et al: Inhibition of clinical benefits of aspirin on first myocardial infarction by nonsteroidal antiinflammatory drugs. Circulation 2003: 108:1191-95.
Aspirin reduces the risk of first myocardial infarction, most likely by irreversible inhibition of the isoenzyme cyclooxygenase-1. Unlike aspirin, nonsteroidal antiinflammatory drugs (NSAIDs) bind reversibly, impairing platelet function only briefly. They share a common docking site, so aspirin may interact competitively with NSAIDs. The authors performed subgroup analysis from a 5-year randomized double blind placebo-controlled trial of 325 mg aspirin on alternate days among over 22,000 healthy male physicians, 92% of whom were Caucasian.
There were 139 confirmed myocardial infarctions in the aspirin group and 239 in the placebo group, with aspirin conferring a 44% reduction in risk of first myocardial infarction. (P<0.00001). In the aspirin group, use of NSAIDs for 1 to 59 days of the year did not increase risk of myocardial infarction (RR 1.21, 95% C.I., 0.78-1.87), but their use for more than 60 days did increase risk (RR 2.86, 95% C.I., 1.25-6.56) compared with no use of NSAIDs. Although these results could be explained by chance or bias, the authors believe that regular, but not intermittent, use of NSAIDs inhibits the cardiovascular clinical benefits of aspirin.