Combination oral contraceptives have been available since 1960. They contain both an estrogen and a progestogen and have been studied extensively in both lower animals and humans and have been the subject of special regulatory requirements for toxicological and clinical studies. The initial oral contraceptives, by today's standards, contained very high levels of both hormones. There has been a continuous decrease in the dose of both the estrogen and the progestogen during the past quarter century, with continued maintenance of high degree of effectiveness. This decrease of dosage has been stimulated by findings from prospective clinical trials and retrospective case control trials. As additional information has been gained with oral contraceptives, new benefits beyond their effectiveness as contraceptives have been realized. Today's oral contraceptives provide a high degree of effectiveness, low incidence of nuisance side effects, and low incidence of major adverse effects.
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