| ATC Code | G03AC08 |
| CAS number | 54048-10-1 |
| PUB number | 6917715 |
| Drugbank ID | DB00294 |
| Empirical formula | C22H28O2 |
| Molar mass (g·mol−1) | 324.464 |
| Physical state | solid |
| Melting point (°C) | 196-200 |
| PKS value | 10.4 |
Etonogestrel is a medication used as a contraceptive in women. It is available as an implant placed under the skin of the upper arm under the brand names Nexplanon and Implanon, and in combination with ethinyl estradiol, an estrogen, as a vaginal ring under the brand names NuvaRing and Circlet. Etonogestrel is effective as a birth control agent within 8 hours of insertion and lasts at least three or four years. After removal, the possibility of conception is restored relatively quickly.
Etonogestrel is a progestogen, i.e. an agonist of the progesterone receptor. It has androgenic activity, but much less than other common progestins (e.g.: levonorgestrel and norethisterone) and does not cause a decrease in sex hormone-binding globulin levels. In addition to its progestagenic and weak androgenic activity, etonogestrel also binds to the glucocorticoid receptor and has very weak glucocorticoid activity. Etonogestrel has no other hormonal activity.
The bioavailability of etonogestrel when administered as a subcutaneous implant or vaginal ring is 100%. Plasma protein binding of the drug is at least 98%, with 66% bound to albumin and 32% bound to sex hormone-binding globulin. Etonogestrel is metabolized in the liver by the enzyme CYP3A4. The elimination half-life of etonogestrel is approximately 25 to 29 hours. After removal of an implant containing etonogestrel, concentrations of the drug were below the limit of detection after one week. Most of etonogestrel is excreted in the urine and a small amount in the stool.
Common side effects of Etonogestrel may include menstrual irregularities, amenorrhea, headache, nausea, breast tenderness, and mood changes (e.g., depression), as well as weight gain, acne, and hirsutism. Etonogestrel may also cause changes in total, LDL, and HDL cholesterol.
Rare side effects of etonogestrel include vaginal infections, contact lens intolerance, vomiting, hair loss, dysmenorrhea, ovarian cysts, and fatigue, while rare side effects include rash, urticaria, and erythema nodosum. Breast discharge, ectopic pregnancy, and exacerbation of angioedema may also occur with the use of etonogestrel.
LD50 (rat, oral): > 2000 mg/kg
Markus Falkenstätter, BSc
Mag. pharm. Stefanie Lehenauer
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