Mifepristone: a potential postcoital contraceptive.
Mifepristone is an orally-active progesterone receptor antagonist. When a single dose of mifepristone is given in the mid- or late follicular phase, it may diminish or inhibit the luteinising hormone (LH) surge. In the early luteal phase, a single dose of mifepristone induces significant changes in the endometrium without affecting the hormonal levels or menstruation. When it is given in the mid-luteal phase, there will also be significant changes in the endometrium and some women may have two episodes of vaginal bleeding. A clinical trial suggests that a single dose of mifepristone in the early luteal phase may be an effective contraceptive agent but the lack of a cheap and easy method to identify the LH surge limits its clinical application. The administration of mifepristone alone or in combination with a prostaglandin does not appear to be an effective form of contraception. When used together with a prostaglandin, it may be an effective method for menstrual regulation but the cost and possible side effects of the prostaglandins limit its use. Mifepristone is a very effective method for emergency contraception. The incidence of side effects was also lower than that of the Yuzpe regimen. Lowering the dose of mifepristone from 600 to 10 mg does not decrease its efficacy but the incidence of delay in onset of the subsequent menses is reduced. Despite its efficacy, the reputation of mifepristone as an abortion pill may limit its access in many countries.
Ho
P C
PC
Department of Obstetrics and Gynaecology, University of Hong Kong. pcho@hkusub.hku.hk
D003267:Contraception / Q000379:methods; D003283:Contraceptives, Postcoital, Synthetic / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008183:Luteal Phase / Q000187:drug effects / Q000378:metabolism; D015735:Mifepristone / Q000737:chemistry / Q000494:pharmacology*
D003283:Contraceptives, Postcoital, Synthetic; D015735:Mifepristone