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- progestin
levonorgestrel
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What is levonorgestrel?
Levonorgestrel is a synthetic progestogen used in contraception. As a form of progesterone, it acts on the hypothalamus, reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, which inhibits ovulation. It also inhibits implantation of fertilized eggs by thickening cervical mucus, blocking sperm from reaching the fallopian tubes.
Levonorgestrel is used in intrauterine devices (IUDs) like Mirena, releasing about 20 micrograms daily for up to five years. It is also in oral contraceptives like Seasonale and emergency contraceptives like Plan B. If taken as a 0.75-mg tablet within 72 hours of unprotected sex, followed by a second tablet within 12 hours, it is about 90 percent effective in preventing pregnancy.
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What is levonorgestrel used for?
Levonorgestrel is a synthetic progestogen used in contraception for women. It impacts the hypothalamus, decreasing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, which inhibits ovulation. It also inhibits implantation of fertilized eggs by thickening cervical mucus, blocking sperm movement to the fallopian tubes.
Levonorgestrel is found in intrauterine devices (IUDs) like Mirena, releasing about 20 micrograms daily for up to five years. It is also in oral contraceptives like Seasonale and emergency contraceptives like Plan B. Plan B is 90% effective when a 0.75-mg tablet is taken within 72 hours of unprotected sex, followed by a second tablet within 12 hours.
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How does levonorgestrel help prevent pregnancy?
Levonorgestrel is a synthetic progestogen that prevents pregnancy through several mechanisms. It acts on the hypothalamus, reducing the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which inhibits ovulation. Levonorgestrel also inhibits implantation of fertilized eggs by preventing them from embedding in the uterine wall. Additionally, it thickens cervical mucus, blocking sperm from traveling into the uterus and fallopian tubes where fertilization typically occurs.
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What forms does levonorgestrel come in (like pills or devices)?
Levonorgestrel is available in several forms, including:
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Intrauterine devices (IUDs) IUDs like Mirena can release levonorgestrel directly into the uterus for up to five years.
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Oral contraceptives It can be found in various oral contraceptive pills, sometimes combined with estradiol. An example is Seasonale, an extended-cycle oral contraceptive.
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Emergency contraceptive pills Levonorgestrel is available as a morning-after pill, such as Plan B.
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Are there any side effects of using levonorgestrel?
Levonorgestrel, a synthetic progestogen used in contraceptives, functions by reducing the secretion of hormones that stimulate ovulation and inhibiting implantation.
Common side effects of levonorgestrel taken orally include changes in menstrual bleeding, such as heavier or lighter periods, nausea, headache, fatigue, and abdominal pain. Levonorgestrel-releasing intrauterine devices (IUDs) do not protect against sexually transmitted diseases and may increase the risk of pelvic inflammatory disease and infection. The efficacy of levonorgestrel may be altered when taken with certain substances, including St. John’s wort, nafcillin, and phenytoin.
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How does levonorgestrel compare to other hormonal birth control methods?
Levonorgestrel is a synthetic progestogen used in various contraceptives, including IUDs, oral pills, and emergency contraception. Like other progestogens, it inhibits ovulation by reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. Levonorgestrel thickens cervical mucus, preventing sperm from fertilizing an egg, and also inhibits implantation of fertilized eggs in the uterus.
Compared to other hormonal birth control methods like combination oral contraceptives (estradiol and progestin), levonorgestrel-only options have different risks and benefits. Combination pills may offer additional benefits, such as reducing the risk of certain cancers, but may also carry more serious risks than levonorgestrel alone.
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levonorgestrel, synthetic progestogen (any progestational steroid, such as progesterone) that is used as a form of contraception in women. Levonorgestrel is the mirror compound (enantiomer) of norgestrel, which was synthesized in the early 1960s by American scientist Herschel Smith at the U.S.-based company Wyeth Pharmaceuticals.
As a form of progesterone, levonorgestrel exerts its actions on the hypothalamus through a negative feedback mechanism, which causes a decrease in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Both LH and FSH normally stimulate ovulation. Thus, by reducing their secretion, levonorgestrel serves to inhibit ovulation. The drug also inhibits implantation, the point when a fertilized egg embeds in the uterine wall, where it will grow and develop into an embryo. In addition, levonorgestrel causes the mucus in the cervix to thicken, which blocks the ability of sperm to travel through the uterus and into the fallopian tubes, where fertilization of the egg by a sperm normally takes place.
In the early 1980s levonorgestrel became widely used in a form of contraception marketed as Norplant. In this system levonorgestrel was implanted beneath the skin of the upper arm in six Silastic (silicone-plastic) capsules, which provided birth control for five years. However, this system has been replaced by Norplant II (Jadelle), which uses a different synthetic progestogen, called etonogestrel, implanted under the skin in specially designed rods the size of matchsticks.
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Today levonorgestrel may be given alone or in a formulation that also contains estradiol. One of the primary uses of levonorgestrel is in intrauterine devices (IUDs), such as Mirena. This particular IUD, once inserted into the uterus, can remain there for up to five years, releasing about 20 micrograms of levonorgestrel daily. Levonorgestrel also is used in various formulations of oral contraceptives, including in combination with estradiol in Seasonale—an extended-cycle oral contraceptive, which enables an 84-day span between menstruations—and in a morning-after pill called Plan B. In 1999 Plan B became available by prescription in the United States. In 2006, after a long politically charged debate, the U.S. Food and Drug Administration approved the sale of Plan B to women (and men) aged 18 and older without a prescription. At least 40 other countries already sold such emergency contraceptives over the counter (Plan B is marketed internationally under a variety of other trade names, including Vikela, Postinor-2, and Imediat N). When a 0.75-mg tablet is taken within 72 hours of unprotected sex, followed by a second 0.75-mg tablet within the next 12 hours, the drug is about 90 percent effective in preventing pregnancy.
The efficacy of levonorgestrel in preventing pregnancy may be altered in the presence of certain substances, including phenytoin (an antiepileptic drug), nafcillin (a penicillin-derived antibiotic), and St.-John’s-wort (an herbal supplement). Similar to other IUDs, levonorgestrel-releasing IUDs do not protect against sexually transmitted diseases, such as HIV/AIDS and herpes simplex. These devices also increase the risk of pelvic inflammatory disease and infection. Levonorgestrel taken orally sometimes causes changes in menstrual bleeding (i.e., heavier or lighter periods). Other common side effects include nausea, headache, fatigue, and abdominal pain.