In 2016, it was the 223rd most commonly prescribed medication in the United States, with more than two million prescriptions. Medical uses
Birth control
At low doses, levonorgestrel is used in monophasic and triphasic formulations of combined oral contraceptive pills, with available monophasic doses ranging from 100 to 250 µg, and triphasic doses of 50 µg/75 µg/125 µg. It is combined with the estrogen ethinylestradiol in these formulations.At very low daily dose of 30 µg, levonorgestrel is used in some progestogen-only pill formulations.Levonorgestrel is the active ingredient in a number of intrauterine devices including Mirena and Skyla. It is also the active ingredient in the birth control implants Norplant and Jadelle.One of the more common forms of contraception that contains only levonorgestrel is an IUD. One IUD, the Mirena, is a small hollow cylinder containing levonorgestrel and polydimethylsiloxane and covered with a release rate controlling membrane. Emergency birth control
Levonorgestrel is used in emergency contraceptive pills (ECPs), both in a combined Yuzpe regimen which includes estrogen, and as a levonorgestrel-only method. The levonorgestrel-only method uses levonorgestrel 1.5 mg (as a single dose or as two 0.75 mg doses 12 hours apart) taken within three days of unprotected sex. With one study indicating that beginning as late as 120 hours (5 days) after intercourse could be effective. However, taking more than one dose of emergency contraception does not increase the chance of pregnancy not happening. Planned Parenthood asserts "Taking the morning-after pill (also known as emergency contraception) multiple times doesnt change its effectiveness, and wont cause any long-term side effects."
As a contraceptive, it works primarily by preventing ovulation and closing off the cervix to prevent the passage of sperm. The endometrial transformation dose of levonorgestrel is 150 to 250 μg/day or 2.5 to 6 mg per cycle.Due to its progestogenic activity, levonorgestrel has antigonadotropic effects and is able to suppress the secretion of the gonadotropins, luteinizing hormone and follicle-stimulating hormone, from the pituitary gland. This in turn, results in suppression of gonadal activity, including reduction of fertility and gonadal sex hormone production in both women and men. The ovulation-inhibiting dose of levonorgestrel in premenopausal women is 50 to 60 μg/day.In men, levonorgestrel causes marked suppression of circulating testosterone levels secondary to its antigonadotropic effects. In healthy young men, levonorgestrel alone at a dose of 120 to 240 μg/day orally for 2 weeks suppressed testosterone levels from ~450 ng/dL to ~248 ng/dL (–45%). Because of its effects on testosterone levels, and due to its androgenic activity being only weak and hence insufficient for purposes of androgen replacement in males, levonorgestrel has potent functional antiandrogenic effects in men. Consequently, it is able to produce adverse effects like decreased libido and erectile dysfunction, among others. In relation to this, levonorgestrel has been combined with an androgen like testosterone or dihydrotestosterone when it has been studied as a hormonal contraceptive in men. Androgenic activity
Levonorgestrel is a weak agonist of the androgen receptor (AR), the main biological target of the androgen sex hormone testosterone.