EARLY TERMINATION OF PREGNANCY WITH MIFEPRISTONE (RU-486) AND THE ORALLY ACTIVE PROSTAGLANDIN MISOPROSTOL

Background and Methods. The combination of mifepristone (RU 486) and a prostaglandin analogue given either intramuscularly or intravaginally is effective in terminating early pregnancy, but the prostaglandin co mponent of the regimen is cumbersome to administer and has side effect s. We conducted two studies to determine the efficacy of 600 mg of mif epristone followed by a small dose of misoprostol, an orally active pr ostaglandin E1 analogue, for the same purpose. In the first study, 505 women who had had amenorrhea for less than 50 days received 400 mug o f misoprostol 48 hours after receiving mifepristone, if the pregnancy was not terminated within that period. In the second study, 390 women initially received the same treatment, but if the pregnancy was not te rminated within four hours after the administration of misoprostol, th ey were offered an additional 200-mug dose of misoprostol. Results. In study 1, the rate of success (termination of pregnancy and complete e xpulsion of the conceptus) was 96.9 percent (95 percent confidence int erval, 94.1 to 97.7 percent) - similar to the success rate of approxim ately 95 percent for mifepristone followed by the intramuscular or int ravaginal administration of prostaglandin. Abortion occurred in 2.9 pe rcent of the women within 48 hours after the administration of mifepri stone, in 60.9 percent within 4 hours after the administration of miso prostol, and in 33.2 percent thereafter. The failures included ongoing pregnancies in four women (0.8 percent) and incomplete abortions in n ine (1.8 percent); two other women (0.4 percent) required vacuum aspir ation for prolonged uterine bleeding. In study 2, pregnancy was termin ated in 5.5 percent of the women before the administration of misopros tol and within four hours after the first dose of misoprostol in 69.1 percent. Among the 71 women who received a second dose of misoprostol, 67 had complete abortions, 2 had partial retention of the conceptus, 1 had synechia with ongoing pregnancy, and 1 had an ectopic pregnancy. One ongoing pregnancy, which was terminated by vacuum aspiration, was recorded among the 27 women who declined to take the second dose of m isoprostol. The overall rate of success of the regimen with the option al second dose of misoprostol was 98.7 percent (95 percent confidence interval, 96.8 to 99.5 percent). No woman had any serious adverse even t. Conclusions. The combination of mifepristone and misoprostol is eff ective for the termination of early pregnancy in terms of success, tol erance, safety, and practicality.