Effect of oral prostaglandin E2 on uterine contractility and outcome of treatment in women receiving RU 486 (mifepristone) for termination of early pregnancy.

It has been shown that the antiprogestin RU 486 (mifepristone) increases the sensitivity of the early pregnant human uterus to the stimulatory action of synthetic prostaglandin E (PGE) analogues. To examine if RU 486 also increases uterine sensitivity to the naturally occurring PGE2 given orally, two investigative approaches were used in the present studies: (i) direct registration of uterine contractions before and after PGE2 administration in untreated and RU 486-treated early pregnant women; and (ii) a double-blind, randomized, controlled efficacy trial involving treatment of pregnant women (amenorrhoea of less than or equal to 49 days) with RU 486 (25 mg twice daily for 4 days) and PGE2 (1 mg once or twice) or placebo on the last day of RU 486 treatment. The results indicate that oral PGE2 at the doses employed had little or no stimulatory effect on uterine contractility and that it did not improve the rate of complete abortion achieved with RU 486 alone. Overall, 25 of 42 women (59%) had a complete abortion, 15 women (36%) did not abort and the remaining two had incomplete abortions. Women with complete abortions had significantly lower pretreatment levels of progesterone and a longer duration of induced bleeding than those who did not abort. Thus oral PGE2, when given in clinically acceptable doses, is not a suitable alternative to synthetic PGE analogues for use in combination with RU 486 for termination of early pregnancy.