The effect of the anti-progestin mifepristone (RU 486) on plasma prostaglandin metabolite levels in early pregnancy and its influence on pregnancy termination.

The effect of a single dose of RU 486 (600mg) on prostaglandin metabolite levels has been studied over a 48 h period in 20 women undergoing medical termination of early pregnancy. The results were compared with controls of similar gestation who were treated surgically. The mean (SD) PGEM levels at 0 and 48 h in the RU 486 group were 13.7 (2.7) and 13.2 (2.2) pg/ml respectively, which was not significantly different from the values of 11.7 (1.1) and 11.3 (0.4) pg/ml measured in the control patients. Similarly the mean (SD) PGFM values of 22.3 (14.7) and 17.0 (7.2) pg/ml at 0 and 48 h were not significantly different from the corresponding control values of 21.9 (13.8) and 23.8 (7.2) pg/ml. In 10 of the study patients, there were no significant changes in PGEM and PGFM concentrations prior to and at 4, 24 and 48 h after RU 486 administration. Although all pregnancies were successfully terminated with the combination of RU 486 and subsequently a vaginal pessary containing PGE1, no stimulation of prostaglandin production could be demonstrated.