The effects of a low-dose monophasic preparation of levonorgestrel and ethinyl estradiol on coagulation and other hemostatic factors

OBJECTIVE: This study was undertaken to evaluate the effects on hemostatic factors of a low-dose preparation of levonorgestrel and ethinyl estradiol in a 12-cycle study. STUDY DESIGN: Thirty healthy women began taking 100 mu g levonorgestrel and 20 mu g ethinyl estradiol on the first day of the menstrual cycle, continued to take the preparation for the next 21 days, and then took placebo for 7 days. Mean changes in prothrombin time, partial thromboplastin time, and levels of factors VII and X, antithrombin, plasminogen, fibrinogen, protein S, thrombin-antithrombin complexes, and D-dimer were analyzed at baseline and at cycles 3, 6, and 12 with paired Student t tests. RESULTS: Factor X, plasminogen antigen and activity, and D-dimer levels were significantly increased (P less than or equal to .01) during all 3 cycle periods. Antithrombin antigen and protein S total antigen levels were significantly (P less than or equal to .001) decreased at cycles 3, 6, and 12, whereas factor VII and protein S activity levels were significantly (P less than or equal to .05) decreased at cycle 3 and at cycles 3 and 6, respectively. CONCLUSION: The effects on hemostatic factors in healthy women of a monophasic preparation of 100 mu g levonorgestrel and 20 mu g ethinyl estradiol were similar to those of other low-dose oral contraceptives.