Enhanced platelet aggregation by oral contraceptives: effect of PG synthetase inhibitors.

Platelet aggregation time was significantly (P less than 0.01) decreased in female rabbits treated with oral contraceptive (a preparation containing low dose of estrogen) as also by injection of diethylstilbestrol (10 mg/kg), while in animals that received indomethacin (10 mg/kg) or aspirin (30 mg/kg) (PG synthetase inhibitors) along with oral contraceptives or diethylstilbestrol there was no significant alteration in platelet aggregation time. The increased synthesis of prostaglandins or some of the intermediary product like TXA2 might be responsible for this effect.