HORMONAL CONTRACEPTION AND PLATELET-FUNCTION

Combination oral contraceptives have been epidemiologically associated with an increased risk of thromboembolic complications. These contraceptives contain both estrogen and a 19-nortestosterone progestin, either of which might be associated with hemostatic changes that are associated with thromboembolic complications (1,2). Epidemiological data seem to suggest that the progestin in particular might be associated with a higher risk of arterial complications such as myocardial ischemia (3). Norplant, a system of six subdermally placed capsules of levonorgestrel, has recently been introduced in the United States after extensive testing and experience. While several hemostatic parameters (increased platelet counts and aggregation, shortened PT and APTT, and a decrease in vitamin K dependent factors) have been reported to be significantly altered among users of levonorgestrel (4,5), platelet alterations have not been studied in depot levonorgestrel users. Hemostatic tests have now been developed that may more closely resemble in vivo conditions (6), including formation of the primary hemostatic plug with the Thrombostat 4000 (6,7) and whole blood aggregation and ATP release (8). The purpose of this study was to examine these functional platelet parameters in patients using oral combined estrogen-progestin and depot progestin-only hormonal contraceptives. © 1995.