Effects of zomepirac on hemostasis in healthy adults and on platelet function in vitro.

Zomepirac, a new nonnarcotic analgesic, was studied in 25 healthy adults for possible effects on hemostasis. Given in a single 200-mg dose or for 15 days at 300 mg/day, zomepirac prolonged template bleeding time and caused transient decreases in platelet adhesiveness, in stimulated platelet aggregation, and in the release of platelet serotonin. The short duration of these effects contrasts with the known week-long duration of the effects of aspirin. Data from in vitro platelet function studies, correlated with plasma level determinations, indicate that these effects on platelet function in man are probably dependent only on the presence of intact zomepirac and not on any metabolites. The qualitative effects of zomepirac on platelets are assumed to be the consequence of reversible inhibition of prostaglandin synthetase in these cells. Platelet concentration and the humoral clotting mechanism were not affected by zomepirac. Although no unusual bleeding has been noted in patients given zomepirc postoperatively, it should be used with the same caution as aspirin in patients with known defects in platelet function or coagulation.