The role of drugs, particularly oral contraceptives, in triggering thrombosis in congenital defects of coagulation inhibitors: a study of six patients.

It is well established that pregnancy and puerperium, surgery and trauma may often trigger thrombotic events even in the normal population. On the other hand, patients with congenital deficiency of clotting inhibitors may develop spontaneous thrombotic episodes, although they become often symptomatic when one of the above-mentioned triggering factors is present. We found this to be true in 40 out of 81 symptomatic patients with congenital defects of coagulation inhibitors. In six (15%) of these cases medications (mainly oral contraceptives) triggered the thrombotic event. The incidence of pharmacological factors as a cause of thrombosis is commonly maintained to be low. This study indicates that this is not so and underlines the potential importance of drugs, particularly oral contraceptives, in the pathogenesis of thrombotic events in patients with congenital defects of clotting inhibitors.