Mifepristone medical abortion requires the use of two drugs: mifepristone and misoprostol. Mifepristone is an antiprogestin taken orally during the first trimester of pregnancy. It blocks receptors of the hormone progesterone. As a result, the lining of the uterus can no longer sustain the growing embryo. The drug also increases prostaglandin levels and dilates the cervix, facilitating abortion. Misoprostol is a prostaglandin analog that is marketed worldwide in over 60 countries for treatment and prevention of gastric ulcers. It is widely used “off-label” for a number of reproductive health indications.
One tablet of mifepristone is swallowed first, causing the embryo to stop growing. Two days later, the woman takes misoprostol, causing contractions of the uterus and expelling the uterine products. The timing, dose, and route of administration of misoprostol often vary slightly. Studies have shown that these drugs effectively terminate more than 9 out of 10 pregnancies in the early first trimester.