Uterine contractility and induction of abortion in early pregnancy by misoprostol and mifepristone

A combination of the antiprogestagen mifepristone and an exogenous prostaglandin given by intramuscular injection or intravaginal pessary is a highly effective means of inducing abortion in early pregnancy. However, the search for a stable oral prostaglandin preparation has been largely unsuccessful. The effect of misoprostol, an orally active prostaglandin used to treat peptic ulcer, on uterine contractility was investigated in 33 women in early pregnancy (under 56 days' amenorrhoea). After administration of misoprostol in doses ranging from 200 micrograms to 600 micrograms, there was a significant increase in uterine pressure. In a second group of women who were given 200-1000 micrograms misoprostol 48 h after the administration of 200 mg mifepristone, there was a significant increase in the amplitude and frequency of uterine contractions. Complete abortion took place in 18 of the 21 women who received misoprostol after mifepristone, but in only 2 of 40 women given misoprostol alone. Our findings show that misoprostol increases uterine activity in early pregnancy and suggest that, in combination with mifepristone, it may be a highly effective method of inducing therapeutic abortion.