RESUMO
To assess the effects of oral contraceptives on anticoagulant treatment the prothrombin times of 12 patients were measured while they were taking both drugs simultaneously and while they were taking only anticoagulants. The mean prothrombin time ratio was significantly higher when patients were taking both drugs than when they were taking only anticoagulants and their doses of anticoagulant were significantly lower. During both periods most of the prothrombin values remained in the therapeutic range. These findings suggest that, contrary to the common belief that oral contraceptives diminish the effects of anticoagulants, contraceptives in fact potentiate the action of the anticoagulants.
PIP: Of 197 patients with heart disease on oral anticoagulant treatment (nicoumalone) 12 were simultaneously taking an estroprogestogenic oral contraceptive. The patients were aged 27-44 years old and anticoagulation control was maintained by measuring prothrombin activity. For 230 months the women took anticoagulant only. The mean prothrombin time ratio was significantly higher when the women were taking both the anticoagulant and the pill than taking only the anticoagulant, but the prothrombin values were in the therapeutic range during both periods. The oral contraceptive seems to potentiate anticoagulation activity not diminish their effect. It is suggested that the estrogen in the pill may produce enzymatic inhibition in microsomes of hepatic cells which potentiate anticoagulant activity through retarded metabolic degradation.
