What is medication abortion and its drug regimen?

Medication abortion is a two-drug regimen that uses the drugs mifepristone1 (aka Mifeprex and RU-486) and misoprostol.2 The regimen begins with mifepristone ingestion, followed 24–48 h later with 800 mcg of misoprostol taken buccally (in the cheek pouch).3 The FDA manages the regimen under the Risk Evaluation and Mitigation Strategy (REMS).

History of mifepristone

1970: Dr. Etienne-Emile Baulieu discovers progesterone receptor (PR) at the University of Paris.4

1980: Dr. George Teutsch synthesizes PR antagonist. The drug is registered as “Roussel Uclaf 38486″ and shortened to RU-486.5

1984: RU-486 conference in Bellagio, Italy. Over thirty RU-486 studies published in conference proceedings.6

1994: Roussel-Uclaf grants Population Council rights to Mifepristone. Population Council grants license to Danco Laboratories.7

2000: The FDA approved mifepristone through seven weeks gestation. The approval required three office visits with a physician and drug dispensed in a health care facility. The FDA required that all serious adverse events be reported.8

2016: The FDA extended approval through ten weeks gestation. They reduced the number of office visits to one and expanded prescribing privileges to any prescriber. The FDA also removed the requirement that prescribers submit adverse event reports (AERs) except in the case of patient death.9

2021: The FDA announced that the modifications to the Mifepristone REMS Program would consist of (1) removing the “in-person dispensing requirement and (2) adding a requirement that pharmacies that dispense the drug be certified.10

2023: The FDA modified the Mifepristone REMS program to remove the restriction that did not allow mifepristone to be dispensed from retail pharmacies.

2024: Walgreens and CVS begin selling Mifepristone in the US.11

Mifepristone effects

Mifepristone (aka Mifeprex, RU486) competes with the mother’s progesterone, a naturally occurring hormone that prepares her body for pregnancy. Progesterone plays a critical role in the normal functioning of the human female reproductive system. It promotes placental development, prepares the uterus for embryo implantation,12 and inhibits uterine contractions.13 Mifepristone is a progesterone receptor antagonist that binds more aggressively to the progesterone receptors in the uterus than progesterone but does not activate the receptor. The primary effect of mifepristone in medication abortion is to cause a separation of the decidua basalis from the trophoblast, which results in the death of the embryo.14 Misoprostol (aka Cytotec) is a prostaglandin E1 analogue that causes cervical softening and uterine contractions, expelling the embryo.15 

Mifepristone contraindications 16

  • Confirmed or suspected ectopic pregnancy
  • Intrauterine device in place
  • Chronic adrenal failure
  • Concurrent long-term corticosteroid therapy
  • Hemorrhagic disorders or concurrent anticoagulant therapy
  • Inherited porphyria
  • History of allergy to mifepristone, misoprostol, other prostaglandins

Mifepristone common side effects (>15% of patients):

  • Nausea, weakness, fever/chills
  • Vomiting, headache, diarrhea, dizziness
  • Severe abdominal pain
  • Vaginal bleeding for 9 -16 days (30+ days for up to 8% of women)

For additional information refer to Medication Abortion Up to 70 Days of Gestation, Questions and Answers on Mifepristone for Medical Termination of Pregnancy Through Ten Weeks Gestation, and Cytotec misoprostol tablets.

NEXT: Can a medication abortion be reversed?

  1. FDA. 2016. “MIFEPREX (mifepristone) Medication Guide.” https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/020687s020lbl.pdf. ↩︎
  2. FDA. 2017. “Cytotec misoprostol tablets.” https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/019268s051lbl.pdf. ↩︎
  3. ACOG. 2020. “Medication Abortion up to 70 Days of Gestation.” https://www.acog.org/en/clinical/clinical-guidance/practice-bulletin/articles/2020/10/medication-abortion-up-to-70-days-of-gestation. ↩︎
  4. Greenhouse, Steven. 1989. “A New Pill, a Fierce Battle.” The New York Times Magazine, February, 22–24, 26. https://pubmed.ncbi.nlm.nih.gov/11646197/. ↩︎
  5. Critchley, H O D, and R R Chodankar. 2020. “90 YEARS OF PROGESTERONE: Selective Progesterone Receptor Modulators in Gynaecological Therapies.” Journal of Molecular Endocrinology 65 (1): T15–33. https://doi.org/10.1530/JME-19-0238. ↩︎
  6. Baulieu E. E., Segal S. J. 1985. The Antiprogestin Steroid RU 486 and Human Fertility Control. Proceedings of a Conference on the Antiprogestational Compound RU486. Oct 23-25. Bellagio, Italy. Reproductive Biology. Published in the series Reproductive Biology. 1984. Sheldon Segal Series Editor. Plenum Press. https://link.springer.com/book/10.1007/978-1-4684-1242-0. ↩︎
  7. Seelye, Katharine Q. 1994. “ACCORD OPENS WAY FOR ABORTION PILL IN U.S. IN 2 YEARS.” The New York Times, May 17, sec. U.S. https://www.nytimes.com/1994/05/17/us/accord-opens-way-for-abortion-pill-in-us-in-2-years.html. ↩︎
  8. https://t.ly/MT_5J. ↩︎
  9. FDA. 2016. “MIFEPREX (mifepristone) Medication Guide.” https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/020687s020lbl.pdf. ↩︎
  10. https://shorturl.at/zKY26. ↩︎
  11. https://shorturl.at/ahtCK. ↩︎
  12. Coomarasamy, A., H. Williams, E. Truchanowicz, P. T. Seed, R. Small, S. Quenby, P. Gupta, et al. 2015. “A Randomized Trial of Progesterone in Women with Recurrent Miscarriages.” New England Journal of Medicine 373 (22): 2141‐2148. https://doi. org/10.1056/NEJMoa1504927 ↩︎
  13. Scarpin, Katherine M., J. Dinny Graham, Patricia A. Mote, and Christine L. Clarke. 2009. “Progesterone Action in Human Tissues: Regulation by Progesterone Receptor (Pr) Isoform Expression, Nuclear Positioning and Coregulator Expression.” Nuclear Receptor Signaling 7 (December): e009. https://doi.org/10.1621/nrs.07009. ↩︎
  14. AAPLOG. 2022. “The Reversal of the Effects of Mifepristone by Progesterone, Practice Guideline 6.” https://aaplog.org/wp-content/uploads/2023/01/ PG-6-Reversal-of-the-Effects-of-Mifepristone- by-Progesterone.pdf.  ↩︎
  15. ACOG. 2020. Medication Abortion Up to 70 Days of Gestation. https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2020/10/medication-abortion-up-to-70-days-of-gestation. ↩︎
  16. FDA. 2016. “MIFEPREX (mifepristone) Medication Guide.” https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/020687s020lbl.pdf. ↩︎