Information about Levonorgestrel
Levonorgestrel is a synthetic progesterone that is used for emergency contraception. Levonorgestrel is also used alone and in combination with estrogens in conventional oral contraceptives.
Liver safety of Levonorgestrel
Use of levonorgestrel for emergency contraception has not been associated with serum enzyme elevations or clinically apparent liver injury with jaundice.
Mechanism of action of Levonorgestrel
Levonorgestrel (lee" voe nor jes' trel) is a synthetic progesterone that is used as a single or as two oral doses within 2 days of unprotected intercourse or contraceptive failure as a means of emergency contraception. Levonorgestrel acts as an agonist of the progesterone receptor and is believed to act by preventing ovulation. In both animal models and in human trials, levonorgestrel appears to be effective only when given before the luteinizing hormone (LH) surge that precedes ovulation and has little or no effect on fertilization or implantation. In large prospective studies, levonorgestrel given in a single or as two doses 12 hours apart lowered the rate of unwanted pregnancies by 50% to 90% of the expected rate, and the effect was seen for as long as 48 hours after unprotected intercourse or suspected contraceptive failure. The overall failure rates of levonorgestrel have ranged from 0.6% to 3.1%, the expected rates being 5% to 6%.
FDA approval information for Levonorgestrel
Levonorgestrel was approved in the United States for use as emergency contraception in 1982 and remains available generically and over-the-counter as tablets of 0.75 and 1.5 mg. The recommended regimen is a total dose of 1.5 mg within 72 hours of the unprotected intercourse or suspected contraceptive failure, given either as a single or split (12 hours apart) oral dose.
Side effects of Levonorgestrel
Side effects are generally mild-to-moderate in severity and can include headache, nausea, abdominal pain, dysmenorrhea, breast tenderness, fatigue, and dizziness.
Clinical use of Levonorgestrel
Levonorgestrel is also used as a progestin in conventional oral contraceptives, administered alone or in combination with estrogens.
Obstetrical and Gynecological Agents
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