Abstract

PIP: The blood clotting systems of 21 women, aged 18 to 38 years, who had begun using oral contraceptives, were studied. 2 brands of oral contraceptives were used, both containing 1 mg progestogen and .08 mg estrogen. Tests were performed before oral contraceptive usage was begun, and again after the tenth and twentieth days. The antithrombin III and thrombin generation results were compared with the records of patients with chronic thromboembolic disease. Oral contraceptives with a quick, dramatic depression of antithrombin activity and an acceleration of thrombin generation within the first cycle. The depression of antithrompin III activity occurred within 7 days, while thrombin generation occurred within 10 days, but was further accelerated by 20 days (p .001). Levels of both returned to normal after discontinuation of oral conceptive use. Results obtained from using oral contraceptives were similar to those of the patients with thromboembolic disease. It was suggested that the change in antithrombin III activity was the most clinically significant of the 2 changes involved.