Mifepristone, also known as RU-486, is a medication typically used in combination with misoprostol to bring about a medical abortion. This combination is effective in terminating a pregnancy up to 10 weeks of gestation. Mifepristone is also used in the management of Cushing's syndrome, endometriosis, and as an emergency contraceptive.
Mifepristone is a progesterone receptor antagonist. It works by blocking the action of progesterone, a hormone necessary for pregnancy to continue. By inhibiting progesterone, mifepristone causes the lining of the uterus to break down, leading to the detachment of the embryo. This process is followed by the administration of misoprostol, which induces uterine contractions to expel the embryo.
Mifepristone is primarily used for medical abortion. It is administered orally, followed by misoprostol 24 to 48 hours later. This regimen is effective in over 95% of cases when used within the first 10 weeks of pregnancy.
In patients with Cushing's syndrome, mifepristone is used to control hyperglycemia secondary to hypercortisolism. It acts by blocking the effects of cortisol at the glucocorticoid receptor.
Mifepristone has been investigated for use in endometriosis, leiomyomas, and as an emergency contraceptive. Its role in these conditions is due to its ability to modulate the effects of progesterone.
Common side effects of mifepristone include nausea, vomiting, diarrhea, abdominal pain, and fatigue. Serious side effects can include heavy bleeding, infection, and incomplete abortion, which may require surgical intervention.
The use of mifepristone for abortion has been subject to significant legal and ethical debate. Its availability varies widely around the world, with some countries having strict regulations or bans on its use.
Mifepristone is well absorbed after oral administration, with peak plasma concentrations occurring approximately 1 to 2 hours post-dose. It is highly protein-bound and metabolized primarily by the liver. The elimination half-life of mifepristone is approximately 18 to 25 hours.
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