Ethinylestradiol

Products

Ethinyl estradiol is present in numerous hormonal contraceptives as an estrogenic component in fixed combination with a progestin. In addition to traditional birth control pills, modern dosage forms such as the contraceptive patch and the contraceptive ring are also on the market. Ethinyl estradiol, unlike the female sex hormone estradiol, has a higher oral bioavailability.

Structure and properties

Ethinyl estradiol (C20H24O2, Mr = 296.4 g/mol) exists as a white to slightly yellowish-white crystalline powder that is practically insoluble in water. It is a derivative of the estrogen estradiol and carries an ethynyl group at the 17α-position. Mestranol is a prodrug of ethinyl estradiol.

Effects

Ethinyl estradiol (ATC G03CA01) has contraceptive and estrogenic properties. The effects of combined hormonal contraceptives are based on inhibition of ovulation, prevention of implantation of the egg in the endometrium, and alteration of cervical secretions. Birth control pills without estrogen, such as the minipill desogestrel, cause increased intermenstrual bleeding. The half-life of ethinyl estradiol is 12 to 14 hours.

Indications

For hormonal contraception.

Dosage

According to the professional information. Various dosing regimens exist. Hormonal contraceptives containing ethinyl estradiol are often given for 21 consecutive days (3 weeks). This is followed by a break of 7 days (1 week), during which withdrawal bleeding begins.

Contraindications

Numerous precautions must be observed during use. Full details can be found in the drug label.

Interactions

Ethinyl estradiol is metabolized and conjugated by CYP3A4. Corresponding drug-drug interactions with CYP inhibitors, CYP inducers, and drugs that affect conjugation are possible. The hormone circulates in the enterohepatic circulation, which may cause interactions with antibiotics.

Adverse effects

The most common adverse effects of combined oral contraceptives include breast pain, weight gain, skin rashes, headache, altered mood, indigestion, and nausea.