COAGULATION AND ANTICOAGULATION EFFECTS OF CONTRACEPTIVE STEROIDS

Epidemiologic data support the notion that first-generation high-dose oral contraceptives (containing >80 mu g of estrogen) increased the in cidence of thromboembolic events. The quantitative interpretation of t hese data is difficult because results were often confounded by life-s tyle factors and inadequate diagnostic procedures. With the introducti on of modern low-dose combination oral contraceptives, the incidence o f thromboembolic events decreased markedly. Although all combined oral contraceptives induce statistically significant changes in hemostatic factors, these changes are generally within normal ranges, and their clinical significance is questionable. Overall, increased activity in hemostatic mechanisms appears to remain in balance. Progestin-only for mulations seem to affect hemostatic parameters to a much lesser degree , and their use has not led to an increased risk of thrombosis. Interi ndividual variations in pharmacokinetics and pharmacodynamics of contr aceptive steroids are great and could tentatively explain why certain persons may be at an increased risk of thrombosis. Although most studi es have looked at steady-state conditions during contraceptive steroid intake, it would seem prudent to investigate further the hemostatic s ystem during a non-steady-state condition, such as that occurring duri ng the first few days of the pill-free interval.