[A new antiprogestational compound, mifepristone (RU-486)].

: RU-486 is a steroid with antiprogestational action synthesized by the French firm Roussel-Ulcaf in 1980. When given in the middle of the menstrual cycle before the peak of luteinizing hormone (LH), it can inhibit ovulation by interfering with the function of the hypothalamus- hypophysis-corpus luteum-endometrium axis. A single dose of RU-486 in the late luteal phase induced uterine bleeding in all cases according to research done by Yen. A single 600 mg im dose of this agent was most effective for inducing abortion. There were positive results up tot he 41st day of amenorrhea in 85-90% of cases, but after the 7th weeks, this percentage declined, dropping to 60% by the 10th week. Advanced pregnancy increased the risk of incomplete expulsion of the conceptus, thus it is advisable to administer RU-486 in combination with a low-dose prostaglandin. Ru-486 is effective in advanced phases of pregnancy; it induces rapid expulsion with minor blood loss or side effects. Uterine bleeding starts 2-3 days after administration, lasting 11.6 + or - 5.8 days, and blood loss exceeds the normal rate in only 3.6% of cases. In 18% of patients, a significant decrease of hemoglobin occurred, but curettage or transfusion was never needed. Increased doses given for a long time produced nausea and asthenia. Possible teratogenic effects in cases of failure await to be investigated. RU-486 could be used for contraception, based on its ability to inhibit ovulation; for post- coital contraception; for regulation of menstruation; and for dilatation of the cervix.