The potential of mifepristone (RU486) as a female contraceptive drug.
This article reviews the development of mifepristone (RU486) as a female contraceptive drug. Mifepristone is an orally active compound with nearly 40% bioavailability after first pass effect. The steady plasma level of mifepristone ranges from 65 nmol/l with 1 mg/day to 1 micromol/l with 10 mg/day and reaches 2.5 micromol/l, 4.5 micromol/l and 5.4 micromol/l with mifepristone 50 mg, 100 mg and 200 mg daily, respectively, over the treatment period. Inhibition of ovulation may be achieved at serum mifepristone concentration of 232.7 nmol/l. Mifepristone appears to antagonise progesterone at the pituitary level to suppress gonadotropin and steroid hormone secretion rather than to act primarily on the hypothalamus to delay or inhibit ovulation. In fact, the endometrium is most sensitive to mifepristone. Low-dose mifepristone impairs luteal phase endometrial development and receptivity by altering endometrial parakine, cytokine and enzyme activity. Thus, low-dose mifepristone can significantly reduce the rate of conception without inhibiting ovulation. However, further research is needed to standardise the dose and dose-schedule to achieve the desired efficacy of low-dose mifepristone for routine clinical use with minimal or no side-effects.
Sarkar
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Department of Reproductive Biology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi.
D017321:Clinical Trials, Phase I as Topic; D003280:Contraceptives, Oral, Synthetic / Q000493:pharmacokinetics / Q000494:pharmacology; D004717:Endometrium / Q000187:drug effects*; D005260:Female; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects; D015735:Mifepristone / Q000493:pharmacokinetics / Q000494:pharmacology; D010053:Ovary / Q000187:drug effects; D010902:Pituitary Gland / Q000187:drug effects
D003280:Contraceptives, Oral, Synthetic; D015735:Mifepristone