The Progesterone Antagonist RU 486

Lynnette K. Nieman, Teresa M. Choate, George P. Chrousos, David L. Healy, Martin Morin, David Renquist, George R. Merriam, Irving M. Spitz, C. Wayne Bardin, Etienne Emile Baulieu, D. Lynn Loriaux

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Since progesterone supports endometrial nidation of the fertilized ovum, a progesterone antagonist would theoretically block this process and thus have contraceptive potential. We have explored the ability of RU 486, a newly developed competitive progesterone antagonist, to function as a contraceptive agent. A single oral dose of 10 mg per kilogram of body weight given in the midluteal phase consistently induced menses within 72 hours in women with normal cycles and no risk of pregnancy. Bleeding was not prevented by administration of human chorionic gonadotropin in the midluteal phase. This suggested that giving a single dose of RU 486 late in the menstrual cycle might be an effective contraceptive strategy. This concept was tested in monkeys. When given to rhesus females on day 25 of the cycle, a single intramuscular dose of RU 486 (5 mg per kilogram) prevented pregnancy. The vehicle-treated control animals had a 28 percent pregnancy rate (P<0.05 by chi-square analysis). No side effects were noted in women or monkeys. These data suggest that a progesterone antagonist such as RU 486 has the potential to be an effective, safe, and convenient contraceptive agent. Further work will be necessary to assess the safety of long-term monthly administration and to define the optimal dose and time of administration in women. (N Engl J Med 1987; 316:187–91.), A SAFE, convenient, and effective method of fertility control has been sought for centuries. No currently available form of birth control, however, is ideal. Oral steroidal contraceptives must be taken daily for maximal effectiveness, and unacceptable side effects increase both with age and with tobacco use.1,2 Intrauterine devices are associated with pelvic inflammatory disease and subsequent decreased fertility.3,4 Barrier methods (condom and diaphragm), although largely free of untoward side effects, have high failure rates related mainly to poor compliance.5 Since progesterone is necessary for nidation of the fertilized ovum, a progesterone antagonist, in theory, could interrupt the hormonal support of…

Original languageEnglish (US)
Pages (from-to)187-191
Number of pages5
JournalNew England Journal of Medicine
Issue number4
StatePublished - Jan 22 1987
Externally publishedYes

ASJC Scopus subject areas

  • Medicine(all)


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