Induction of abortion with mifepristone (RU 486) and oral or vaginal misoprostol

N Engl J Med. 1995 Apr 13;332(15):983-7. doi: 10.1056/NEJM199504133321502.


Background: Medical termination of pregnancy can be successfully performed with a combination of mifepristone (RU 486) and a prostaglandin analogue. We conducted a prospective, randomized trial to compare oral with vaginal administration of the prostaglandin E1 analogue misoprostol for first-trimester abortion in women treated initially with mifepristone.

Methods: The study population consisted of 270 women seeking abortion within 63 days after the onset of amenorrhea. The dose of mifepristone was 600 mg, and the dose of misoprostol was 800 micrograms. The study had two primary end points: expulsion of the conceptus without the need for a surgical procedure, and abortion within four hours after the administration of misoprostol.

Results: Expulsion of the conceptus without the need for a surgical procedure occurred in 95 percent of the women who received misoprostol vaginally and in 87 percent of those who received it orally (P = 0.03). The rate of continued pregnancy was 7 percent with the oral regimen and 1 percent with the vaginal regimen (P = 0.01). Ninety-three percent of the women receiving misoprostol vaginally had abortions within four hours, as compared with only 78 percent of the women receiving the drug orally (P < 0.001). Vomiting and diarrhea were reported more frequently by the women who received oral misoprostol than by those who received vaginal misoprostol (P = 0.04 and P = 0.002, respectively).

Conclusions: After the administration of mifepristone, vaginal administration of misoprostol is more effective and better tolerated than oral administration for the induction of first-trimester abortion.

PIP: During June 1993-January 1994 in Scotland, clinicians recorded data on 270 women attending the fertility control clinic at Aberdeen Royal Hospitals for voluntary termination of early pregnancy (within 63 days from onset of amenorrhea). They received 600 mg of oral RU-486 on day 1 and either 800 mcg of oral misoprostol or 800 mcg misoprostol inserted deep into the vagina 36-48 hours later. Researchers wanted to compare the safety and efficacy of 800 mcg oral misoprostol with the safety and efficacy of 800 mcg vaginal misoprostol in women who had previously received RU-486. 2.6% aborted before receiving misoprostol. Complete abortion without surgical intervention was more frequent in the vaginal misoprostol group than the oral misoprostol group (95% vs. 87%; p = 0.03). The continued pregnancy rate was lower in the vaginal misoprostol group than the oral misoprostol group (1% vs. 7%; p = 0.01). Expulsion of the conceptus was more likely to occur within 4 hours of receiving misoprostol among the vaginal group than the oral group (93% vs. 78%; p 0.001). The oral misoprostol group had a higher incidence than the vaginal misoprostol group of vomiting (44% vs. 31%; p = 0.04) and diarrhea (36% vs. 18%; p = 0.002). The two groups did not differ significantly with respect to other side effects or severity of symptoms. The women in the oral misoprostol group were more likely to think that the antiemetic drug took minutes rather than 1 or more hours to act than those in the vaginal misoprostol group (61% vs. 34%; p 0.001). These findings show that, following administration of RU-486, vaginal misoprostol was better tolerated and more effective than oral misoprostol at inducing abortion in women in the first trimester of pregnancy.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Abortion, Induced*
  • Administration, Intravaginal
  • Administration, Oral
  • Adult
  • Confidence Intervals
  • Diarrhea / chemically induced
  • Female
  • Follow-Up Studies
  • Humans
  • Mifepristone* / administration & dosage
  • Mifepristone* / adverse effects
  • Misoprostol* / administration & dosage
  • Misoprostol* / adverse effects
  • Pregnancy
  • Prospective Studies
  • Vomiting / chemically induced


  • Misoprostol
  • Mifepristone