The aim of this work is to evaluate the effects on coagulation and fibrinolysis of the oral contraceptives of third generation in Brazilian women and the impact on these effects by reducing ethinyl estradiol dosage. Eleven Brazilian women taking monophasic oral contraceptive containing 20 µg of ethinyl estradiol combined with 150 µg of desogestrel for six cycles consecutively entered this study. The effects on parameters pro-coagulants, anticoagulants, pro-fibrinolytics and fibrin turnover index were evaluated. The results from oral contraceptive increased significatively the factors VIII, IX, X and XII. With respect to coagulation inhibitors, no antithrombin changes were noted in both groups, increase in the levels of protein C and decrease in the levels of protein S total were noted. Concerning the fibrinolytic parameters, the oral contraceptive increased the plasminogen activity, although no changes on t-PA, and alpha-2-antiplasmin were observed. Similary, no changes on the levels of fibrin degradation products were observed, thus indicating that oral contraceptives did not interfere with generation and degradation of fibrin. The results obtained indicate that the oral contraceptives studied did not promote enough pro-fibrinolytic changes so as to state that a re-establishment occurs on haemostatic balance. Therefore, we suggest the use of this oral contraceptive can result in thromboembolic episode mainly in association with other factors such as congenital deficiency of natural clotting inhibitor antithrombin, protein C or protein S.
Contraceptives; coagulation; fibrinolysis
