How Medication Abortion with RU-486/Mifepristone Works
A step-by-step look at how these drugs end pregnancy
Editor’s Note (03/15/23): A judge in Texas will hear arguments today in a case that could restrict access to the abortion drug mifepristone and threaten the U.S. Food and Drug Administration’s authority. In this opinion piece published last year, we explained how mifepristone works in combination with the drug misoprostol.
In 2016 the U.S. Food and Drug Administration approved a two-drug combination of Mifeprex (also called RU-486 or mifepristone) and Cytotec (commonly known as misoprostol) to induce abortion without surgery. In 2019 the Centers for Disease Control and Prevention reported that approximately 42 percent of all abortions in the U.S. were medication-based.
To start the process, a person takes mifepristone within 10 weeks from their last period. One or two days later they take misoprostol. Both drugs work individually, but they are more effective together. Mifepristone blocks progesterone’s action on the uterus, making it incapable of supporting a pregnancy. Misoprostol, among other things, starts uterine contractions.
Research has shown medication abortion to be safe and effective. According to a 2015 study from the University of California, Los Angeles, 99.6 percent of more than 30,000 women who were seeking a medication abortion were able to terminate their pregnancies. In a review of clinical trials published in 2013, using mifepristone and misoprostol together, just 0.3 percent of the more than 45,000 women studied had complications that required hospitalization. The treatment did occasionally fail if the pregnancy was longer than eight weeks or if the instructions weren’t followed. The mortality rate of the medications is less than 0.001 percent.