Mifepristone (RU 486) compared with high-dose estrogen and progestogen for emergency postcoital contraception.
BACKGROUND
Mifepristone (RU 486) is a synthetic steroid with potent antiprogestational and antiglucocorticoid properties that provides an effective medical method of inducing abortion in early pregnancy. Since progesterone is essential for implantation, we tested the use of mifepristone for emergency postcoital contraception.


METHODS
We studied 800 women and adolescents requesting emergency postcoital contraception who had had unprotected intercourse within the preceding 72 hours. A total of 398 women and adolescents were randomly assigned to treatment with 100 micrograms of ethinyl estradiol and 1 mg of norgestrel, each given twice 12 hours apart (standard therapy), and 402 women and adolescents were randomly assigned to receive 600 mg of mifepristone.


RESULTS
None of the women and adolescents who received mifepristone became pregnant, as compared with four of those who received standard therapy; the difference in failure rates between the two regimens was not statistically significant. The number of pregnancies in each group was significantly lower than the number expected according to calculations based on the day of the cycle during which intercourse had taken place (P less than 0.001). In many subjects the stage of the cycle as calculated by menstrual history was inconsistent with measurements of plasma progesterone or urinary pregnanediol excretion. The subjects treated with mifepristone reported less nausea (40 percent vs. 60 percent) and vomiting (3 percent vs. 17 percent) on the day of treatment, as well as lower rates of other side effects, than the subjects treated with the standard regimen, but they were more likely to have a delay in the onset of the next menstrual period (42 percent vs. 13 percent).


CONCLUSIONS
Mifepristone is a highly effective postcoital contraceptive agent that, if used more widely, could help reduce the number of unplanned and unwanted pregnancies.
Glasier
A
A
Department of Obstetrics and Gynaecology, University of Edinburgh, Scotland, United Kingdom.
Thong
K J
KJ
Dewar
M
M
Mackie
M
M
Baird
D T
DT
D000293:Adolescent; D000328:Adult; D003282:Contraceptives, Postcoital, Hormonal / Q000009:adverse effects; D004630:Emergencies; D004997:Ethinyl Estradiol / Q000009:adverse effects; D005260:Female; D006801:Humans; D008598:Menstruation / Q000187:drug effects; D008875:Middle Aged; D015735:Mifepristone / Q000009:adverse effects; D009644:Norgestrel / Q000009:adverse effects; D011247:Pregnancy; D011275:Pregnancy, Unwanted; D011276:Pregnanediol / Q000652:urine; D011374:Progesterone / Q000097:blood; D011897:Random Allocation
D003282:Contraceptives, Postcoital, Hormonal; D015735:Mifepristone; D009644:Norgestrel; D004997:Ethinyl Estradiol; D011374:Progesterone; D011276:Pregnanediol