Anti-progesterones have potential as contraceptives, acting either by the inhibition of ovulation or the inhibition of endometrial development. Clinical studies have shown that once-a-month treatment with Mifepristone in the early luteal phase is an effective contraceptive method, and that emergency post-coital contraception with Mifepristone is at least as effective as other methods currently used. Recent studies indicate that the endometrium is more susceptible to Mifepristone than are the hypothalamic and pituitary regions, and it may therefore be possible to develop a new contraceptive method based on low daily or once-weekly doses of Mifepristone that does not influence ovarian function.
PIP: The anti-progestin Mifepristone has demonstrated efficacy in inducing early abortion when administered in conjunction with prostaglandin analogues. Also possible, although less researched, is use of Mifepristone as a contraceptive agent. Modes of action include inhibition of ovulation by a long-term daily or intermittent high dose, endometrial contraception by a high Mifepristone dose in the early luteal phase, endometrial contraception by the long-term use of daily or weekly administration of low doses of Mifepristone that do not inhibit ovulation, or a high dose as emergency post-coital contraception. The available research on each of these approaches is reviewed in this article. The most recent studies indicate that the endometrium is more susceptible to Mifepristone than the hypothalamic and pituitary regions, suggesting the feasibility of low daily or once-weekly doses of Mifepristone that do not influence ovarian function.