The evolution of oral contraceptives. Maximizing efficacy, minimizing risks.

No single pharmacologic agent has been more widely studied than the oral contraceptive (OC). Scientific efforts have been directed primarily toward maximizing the benefits of OCs--which remain the most effective, reversible form of birth control--while minimizing their potential risks, specifically thromboembolic disorders and cardiovascular disease. Decreases in the dose of estrogen from the 100 micrograms--150 micrograms levels of the 1960s to the 30 micrograms--50 micrograms formulations of today have been accompanied by dramatic reductions in the risk of thromboembolic events. In healthy women not predisposed to these conditions, the risk of thromboembolism is now considered very small. Similar reductions in the doses of progestin have also resulted in decreases in the incidence of stroke and myocardial infarction. Evidence suggests that not only dose but androgenic activity of a progestin may negatively impact on risk of cardiovascular disease. Thus development of OCs containing a progestin with the least potential for androgenically mediated side effects appears to be advisable.