Over the 30 years since combined oral contraceptives (OCs) first emerged, scientists have learned that reducing the estrogen component by 80% and the progestogen component by 90% provides adequate contraception and reduces adverse side effects. Their better understanding of the mechanisms of the metabolism of estrogens and progestogens contained in these OCs has allowed them to develop new progestogens, all modifications of levonorgestrel. These new progestogens include desogestrel, gestodene, and norgestimate which further reduce the likelihood of androgenic side effects and adverse changes of blood lipids, coagulation, and carbohydrate metabolism. They were first introduced in Europe and are expected to be approved by the US Food and Drug Administration soon. The improved understanding of the metabolic mechanisms has also allowed scientists to learn about the role of the cytochrome P-450 hydroxylating enzyme system in steroid metabolism and about interactions of OCs with other drugs. This hepatic system 2-hydroxylates ethinyl estradiol and eliminates it more rapidly from the body; so inhibiting 2-hydroxylase activity would make ethinyl estradiol more powerful, while stimulating it would reduce ethinyl estradiol's potency. This discovery alerts physicians to be cautious when prescribing other medications, while a woman is taking an OC, that could induce or inhibit this enzyme system, e.g., rifampicin (an inducer) and cimetidine (an inhibitor). Scientific documentation for a justification of the pill-free interval does not exist. Disadvantages of the pill-free interval include estrogen withdrawal symptoms, e.g., migraine headaches and the risk of reduced contraceptive efficacy.
|Original language||English (US)|
|Number of pages||7|
|Journal||Current Opinion in Obstetrics and Gynecology|
|Publication status||Published - 1992|
ASJC Scopus subject areas
- Obstetrics and Gynecology