Mifepristone is under scrutiny in the courts, but it has been used safely and effectively around the world for decades

A flurry of court rulings in April 2023 has left the future of the abortion pill mifepristone in question. For now, a U.S. Supreme Court decision on April 21 allows the drug to remain accessible without additional restrictions as the merits of the case are weighed in lower court proceedings.

Depending on the outcome, the pill could face a ban or tightened restrictions on its usage, a possibility that has many health care providers concerned.

The Conversation asked Grace Shih, a family physician practicing in Washington state, to explain the science behind mifepristone as well as its safety and efficacy in medication abortions.

Mifepristone is a pill that is used in medication abortion during early pregnancy. It was initially approved by the Food and Drug Administration in 2000 and is approved by the FDA for medication abortion up to 10 weeks after the first day of the last menstrual period.

It can be taken as one part of a two-part pill regimen for medication abortion. Mifepristone is prescribed as a 200-milligram dose taken orally, followed by an 800-microgram dose of misoprostol, which is placed in the vagina or between the teeth and cheek, where it dissolves and is absorbed, usually 24 to 48 hours later.

Mifepristone acts by blocking the hormone progesterone, which is necessary for a pregnancy to develop. This stops the pregnancy growth and softens and dilates the cervix. It also prepares the uterus for contractions, increasing its sensitivity to medications such as misoprostol.

Misoprostol is a synthetic prostaglandin. Prostaglandin is a hormonelike substance that has multiple effects, including the stimulation of uterine contractions, which helps expel pregnancy tissue such as the thickened uterine lining and the tissues that are the precursor to the placenta.

Misoprostol is currently FDA-approved for reducing the risk of gastric ulcers in patients who are at high risk of complications from ulcers. But it is commonly used off-label for things like cervical ripening, or softening, to induce or help with labor. Mifepristone and misoprostol are also both used in the medical management of miscarriage.

Medication abortion can also be done with misoprostol alone, an approach known as the misoprostol-only regimen. This regimen is safe and has been used widely by people around the world. In the misoprostol-only regimen, an 800-microgram dose is placed in the vagina or between the teeth and cheek every three hours for up to three doses.

Both protocols are very effective, with the two-drug regimen up to 99.6% effective and the misoprostol-alone regimen between 84% to 96% in medication abortions.

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