Pharmacokinetics of ethinyl estradiol and mestranol

Article Abstract:

Oral contraceptives contain derivatives of two female reproductive hormones, one of which is estrogen. Currently, all contraceptives use versions of estrogens which contain ethinyl chemical groups, as these improve the effects on the pituitary and reproductive hormones, and also boost the effects of some forms of the other contraceptive component, progesterone. This boost, or amplification, has allowed the formulation of low-dose contraceptives, with the idea of minimizing estrogenic side effects. However, it is important to understand the pharmacokinetics, or tissue handling properties, of ethinyl estrogens before the relationship between dose and side effect can be appreciated. A confounding problem is that there is a large variation among individuals in the body's handling of the estrogens, and this is not usually considered in studies of responses to estrogen doses. Mestranol is a form of estrogen, or estradiol, which is inactive as such but which is metabolized by the body to ethinyl estradiol. The pharmacokinetics of mestranol has not been well-studied. In a study of 24 women who took contraceptives containing 35 milligrams (mg) of ethinyl estradiol (EE) and 27 who took pills containing 50 mg of mestranol, the actual bioavailability of the 50 mg of mestranol was equivalent to the 35 mg of estrogen, that is, it had a 70 percent yield or effectiveness. Some studies of contraceptives have looked at contraceptive effects without regard to the type of estrogen used. This study indicates that so-called high-dose mestranol pills may have lower available estrogen levels than low-dose EE formulations. Much more data is available on the body's disposition of EE, and this information is reviewed. Study of a sulfated form of EE, which may have higher levels in blood than EE itself, show that it is unlikely to act as a reservoir to supply EE, as it is removed from the circulation too rapidly. There are differences among people of different ethnic backgrounds in EE handling, indicating that much more needs to be learned about how this drug is absorbed, metabolized, distributed, and excreted. (Consumer Summary produced by Reliance Medical Information, Inc.)

Ethinyl estradiol, Mestranol

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Activated protein C resistance assay when applied in the general population

Article Abstract:

Screening populations for the presence of factor V Leiden to prevent deaths from blood clots may not be cost effective. The presence of factor V Leiden in blood indicates resistance to the anticoagulant properties of activated protein C, a condition which can lead to easily formed blood clots especially during pregnancy or when taking oral contraceptives. Researchers estimated the cost effectiveness of screening three hypothetical populations. A population with a 2% rate of factor V Leiden would have a false-positive rate of 56% and screening would cost $44,180,000 to prevent one death from blood clots.

Analysis, Diagnosis, Thrombosis, Protein C

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The effect of fluconazole on circulating ethinyl estradiol levels in women taking oral contraceptives

Article Abstract:

Fluconazole may cause an increase in blood levels of ethinyl estradiol in women taking oral contraceptives. Fluconazole is an oral antifungal drug commonly used to treat vaginal yeast infections. Researchers gave a single dose of fluconazole to 19 women taking Ortho-Novum 7/7/7 (Ortho Pharmaceutical) or Triphasil (Wyeth-Ayerst Laboratories) birth control pills, and measured the effect on the estrogen hormone level in their blood. After fluconazole, maximum and average blood levels of ethinyl estradiol were higher.

Usage, Causes of, Complications and side effects, Drug interactions, Fluconazole, Ortho-Novum 7/7/7 (Contraceptive)

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