| Item |
Information |
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Drug Groups
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approved; investigational |
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Description
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A progestational and glucocorticoid hormone antagonist. Its inhibition of progesterone induces bleeding during the luteal phase and in early pregnancy by releasing endogenous prostaglandins from the endometrium or decidua. As a glucocorticoid receptor antagonist, the drug has been used to treat hypercortisolism in patients with nonpituitary cushing syndrome. [PubChem] |
| Indication |
For the medical termination of intrauterine pregnancy through 49 days' pregnancy. Also indicated to control hyperglycemia secondary to hypercortisolism in adult patients with endogenous Cushing's syndrome who have type 2 diabetes mellitus or glucose intolerance. |
| Pharmacology |
Mifepristone is a synthetic steroid with antiprogestational effects indicated for the medical termination of intrauterine pregnancy through 49 days' pregnancy. Doses of 1 mg/kg or greater of mifepristone have been shown to antagonize the endometrial and myometrial effects of progesterone in women. During pregnancy, the compound sensitizes the myometrium to the contraction-inducing activity of prostaglandins. Mifepristone also exhibits antiglucocorticoid and weak antiandrogenic activity. The activity of the glucocorticoid dexamethasone in rats was inhibited following doses of 10 to 25 mg/kg of mifepristone. Doses of 4.5 mg/kg or greater in human beings resulted in a compensatory elevation of adrenocorticotropic hormone (ACTH) and cortisol. |
| Toxicity |
Nearly all of the women who receive mifepristone will report adverse reactions, and many can be expected to report more than one such reaction. About 90% of patients report adverse reactions following administration of misoprostol on day three of the treatment procedure. Side effects include more heavy bleeding than a heavy manstrual period, abdominal pain, uterine cramping, nausea, vomiting, and diarrhea. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Hepatic. Hepatic, by Cytochrome P450 3A4 isoenzyme to the N-monodemethylated metabolite (RU 42 633); RU 42 698, which results from the loss of two methyl groups from position 11 beta; and RU 42 698, which results from terminal hydroxylation of the 17–propynyl chain. |
| Absorption |
The absolute bioavailability of a 20 mg oral dose is 69% |
| Half Life |
18 hours |
| Protein Binding |
98% (bound to plasma proteins, albumin and a 1-acid glycoprotein) |
| Elimination |
Fecal: 83%; Renal: 9%. |
| References |
| • |
Fiala C, Gemzel-Danielsson K: Review of medical abortion using mifepristone in combination with a prostaglandin analogue. Contraception. 2006 Jul;74(1):66-86. Epub 2006 May 19.
[Pubmed]
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| • |
Heikinheimo O, Kekkonen R, Lahteenmaki P: The pharmacokinetics of mifepristone in humans reveal insights into differential mechanisms of antiprogestin action. Contraception. 2003 Dec;68(6):421-6.
[Pubmed]
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| • |
Chabbert-Buffet N, Meduri G, Bouchard P, Spitz IM: Selective progesterone receptor modulators and progesterone antagonists: mechanisms of action and clinical applications. Hum Reprod Update. 2005 May-Jun;11(3):293-307. Epub 2005 Mar 24.
[Pubmed]
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| • |
Spitz IM, Bardin CW, Benton L, Robbins A: Early pregnancy termination with mifepristone and misoprostol in the United States. N Engl J Med. 1998 Apr 30;338(18):1241-7.
[Pubmed]
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| • |
Piaggio G, von Hertzen H, Heng Z, Bilian X, Cheng L: Meta-analyses of randomized trials comparing different doses of mifepristone in emergency contraception. Contraception. 2003 Dec;68(6):447-52.
[Pubmed]
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| External Links |
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