RESUMEN
OBJECTIVE: To evaluate the effects of two preparations of combined oral contraceptives (COCs), the monophasic COC containing 30 micrograms ethinylestradiol and 75 micrograms gestodene and the triphasic COC containing 30/40/30 ethinylestradiol and 50/70/100 micrograms gestodene on seven natural inhibitors and hemostatic variables. METHOD: Forty-four healthy young women, randomly allocated into two groups (A and B) received the two preparations of COCs, respectively. The following variables were tested in a basic examination and at 1-, 3- and 6-month intervals to evaluate the role of the above preparations on the hemostatic balance of prothrombin time, fibrinogen, antithrombin III activity, protein C activity, total protein S antigen, plasminogen activity and lupus anticoagulant. RESULTS: Group A women presented shorter prothrombin time at 6 months, an increased fibrinogen level at 3 months, no influence on the anticoagulant factors, antithrombin III, protein C and total protein S and an increased plasminogen activity at the 1st and 3rd months of treatment. On the other hand, group B women presented shorter prothrombin time at 3 months, no increase in fibrinogen, a decrease in antithrombin III activity and total protein S activity at the 6th month, whereas protein C and plasminogen activities were found to be increased at the 3rd and 1st, 3rd and 6th month, respectively. CONCLUSIONS: The study did not find differences between the two treatment groups, for the evaluated parameters. This finding is clearly important in the light of the recent epidemiological reports on third-generation COCs. However, differences were found among the various periods of administration of both COCs.