What is misoprostol? Crucial questions about the other abortion drug.

A series of legal challenges working their way through the federal courts and now taken up by the Supreme Court has raised questions about the future of access to mifepristone, an abortion medication that is used in more than half of all US abortions with high effectiveness and few severe side effects.

Mifepristone is the first of two drugs usually prescribed together to induce an abortion. The second, misoprostol, however, can be used to terminate a pregnancy on its own. The fate of mifepristone has been in limbo since April, and abortion providers have since scrambled to prepare for a new set of logistics and side effects that might accompany misoprostol-only abortion — all while evaluating the legal risks of providing a medication that is now sure to face increased scrutiny.

The challenges to mifepristone’s availability began when a federal judge in Texas, Matthew Kacsmaryk, ruled to suspend the Food and Drug Administration’s approval of the drug, which has been on the market for more than 20 years in the US. The Supreme Court eventually intervened and has ordered that the medication continue to be available as lower courts sort out the matter. In December, the high court announced that it would hear two consolidated challenges to the availability of mifepristone, FDA v. Alliance for Hippocratic Medicine and Danco Laboratories v. Alliance for Hippocratic Medicine, in full — the biggest case it will hear since overturning Roe v. Wade in June 2022.

The Texas lawsuit heard by Kacsmaryk and filed by the Alliance for Hippocratic Medicine, an anti-abortion group, also sought to ban the use of misoprostol in abortions, but the group did not ask the judge to rescind the medication’s FDA approval, and Kacsmaryk’s ruling addressed only mifepristone. Abortion rights groups, however, say they expect that opponents of the procedure will continue to try to ban the use of misoprostol in abortions.

“Anything could happen,” Farah Diaz-Tello, senior counsel and policy director at the reproductive justice legal group If/When/How, told Vox this spring. “I wouldn’t put anything past them at this point.”

With another sea change in abortion access potentially on the horizon, here are answers to some common questions about the drug.

What is misoprostol?

Before the Texas lawsuit, the FDA-approved protocol for medication abortion consisted of a dose of mifepristone to stop the pregnancy from progressing, followed 24 hours later by up to two doses of misoprostol to induce contractions and cause the uterus to empty.

The two drugs work in concert to end a pregnancy, but they have very different histories. Mifepristone was developed in the 1980s in France specifically as an abortion drug, and was approved for use in the US in 2000. Misoprostol, however, was developed in the 1970s to treat stomach ulcers. Its use in abortion was pioneered by a group of feminists in Brazil, where surgical abortions were largely inaccessible, said Ushma Upadhyay, a professor with Advancing New Standards in Reproductive Health at the University of California San Francisco.

While mifepristone was tightly regulated even before the Texas lawsuit, misoprostol is available with a prescription at most US pharmacies. It is also available over the counter in many other countries, including Mexico. “It has been used around the world for abortion for many years because it is so much more easily available and cheaper” than mifepristone, Upadhyay said.

Can misoprostol end a pregnancy on its own?

Misoprostol alone is only slightly less effective at terminating a pregnancy than the two-drug combination. While mifepristone and misoprostol together successfully lead to an abortion 95 to 97 percent of the time, misoprostol on its own can be up to 93 percent effective, Upadhyay and her colleagues wrote in a recent paper.

Is misoprostol safe?

Misoprostol-only abortions are also largely safe, with just 0.7 percent of patients requiring hospitalization or a blood transfusion, according to the paper. The World Health Organization includes misoprostol-only procedures among its recommended methods of abortion, and the drug is commonly used on its own around the world.

The biggest concern with misoprostol-only abortions is the side effects. “When the mifepristone doesn’t act to begin the process of separating the pregnancy,” Upadhyay told Vox, “you’re just relying on those uterine contractions alone.” That means more intense pain and bleeding spread out over a longer period, and in some cases, diarrhea, nausea, and vomiting.

Because many patients, especially in more conservative states, have to travel long distances to obtain abortion medication, the increase in side effects is especially onerous. Patients could face the prospect of driving themselves hundreds of miles while experiencing intense bleeding and pain. “It’s a lot for a patient,” Upadhyay said. “It could make the whole journey unfeasible.”

How will patients get misoprostol?

In the current chaotic climate around abortion access, there’s the question of obtaining the pills at all. Some abortion providers have said they will not offer misoprostol-only procedures “because they feel that they’re being forced to offer patients care that is not within their comfort zone,” Upadhyay said. Other providers, like the Trust Women clinic in Wichita, Kansas, have said they would offer misoprostol-only abortions if mifepristone became unavailable. They will need to retrain staff, however, to administer the new protocol, which involves more doses of misoprostol, and to inform patients about side effects.

Several telehealth companies, including Hey Jane and Carafem, provide abortion medication by mail in states where it is legal and say they are ready to provide misoprostol-only regimens if mifepristone is removed from the market. As Vox’s Rachel M. Cohen has reported, patients can also continue getting both medications from the nonprofit Aid Access, which avoids US restrictions by prescribing pills from overseas.

In the event of reduced access to mifepristone, more patients will likely choose to self-manage their abortions, obtaining pills online, through friends, or in another country where they are more readily available, Diaz-Tello said. While data on self-managed abortion with misoprostol alone is difficult to come by, “it’s certainly something that people are already aware of,” she said. “The history of using misoprostol to end a pregnancy is deeply intertwined with self-managed abortion and people finding ways to self-determine their reproductive lives in the face of restrictive abortion laws.”

Self-managed abortion can be a safe option, but it exposes people to legal risks, Diaz-Tello said. While it is not explicitly illegal in most states, prosecutors have used feticide laws and other statutes to charge people who take abortion medication outside of a clinical setting. The Texas ruling doesn’t change the laws around self-managed abortion and doesn’t make either mifepristone or misoprostol illegal to possess, Diaz-Tello said. But the case could result in additional scrutiny around abortion medication that could cause people who self-manage to “be criminalized, irrespective of what the law says.”

Will anti-abortion groups try to ban misoprostol?

Abortion opponents have signaled their eagerness to stop medication abortions, and they are likely to continue to target misoprostol as well as mifepristone. Misoprostol might be more difficult to fully remove from the market because of its common use as an ulcer medication, but anti-abortion lawmakers could still restrict its use.

A recent Kentucky law, for example, requires health care providers to document the indications for which abortion-inducing drugs were prescribed, Diaz-Tello said. Other states could follow suit and attempt to ban misoprostol from being prescribed for use in an abortion. Anti-abortion groups have also floated other strategies, including petitioning the FDA to require doctors who prescribe abortion pills to bag any fetal tissue as medical waste, Cohen reported. Such a requirement would likely have a chilling effect on abortions since it would be almost impossible for providers to follow.

Indeed, while the cases the Supreme Court will consider do not directly target misoprostol, it’s a sign of where the anti-abortion movement is going, Diaz-Tello said. “What this lawsuit is telling us is that no tactic is off the table.”

Update, December 13, 10:50 am ET: This story was originally published on April 8 and has been updated multiple times, most recently to reflect the Supreme Court’s announcement that it would hear lawsuits seeking to ban mifepristone.