An update on the use of antigestagens in fertility control.

The current status of antiprogestagens in fertility control: inhibition of ovulation postcoital contraception once-a-month pill induced abortion cervical ripening and induction of labor is reviewed. There are 2 types of antigestagens those that inhibit progesterone synthesis by inhibiting 3beta-hydroxysteroid dehydrogenase and those that compete for the progesterone receptors. Epostane is a progesterone synthesis inhibitor developed by Sterling Winthrop Guildford UK which effectively terminates human pregnancy but the company is not planning to market it. RU-486 (Roussel-Uclaf Paris) as well as 2 compounds developed by Schering Ag Berlin are effective receptor antagonists but only RU-486 has been extensively tested clinically. RU-486 has been shown to inhibit the LH surge yet is not expected to be a good ovulation suppressant because of anti-glucocorticoid activity and unopposed estrogen. It is only 80% effective postcoitally and 85% effective as a once-a-month pill. RU-486 has been licensed in France and the Peoples Republic of China as an abortifacient combined with prostaglandins up to 49 days since LMP. It has been shown to be just as effective up to 56 days. Research is in progress to find a delayed- release system for the prostaglandin needed 48 hours later. RU-486 is effective in cervical ripening reducing the dose of PG needed for midtrimester abortion by 50% and cutting the time to abortion from 15.8 to 6.8 hours. It also induces labor in case of intrauterine death of fetal abnormality enhancing the action of oxytocin. Roussel-Uclaf is not planning to introduce production of RU-486 in any other countries because of threatened violence and boycotts by extremist pro-life groups.