Misoprostol is a prostaglandin E₁ (PGE₁) analogue used for the treatment and prevention of stomach ulcers. It is currently marketed by Pfizer under the trade name Cytotec.

When administered, misoprostol stimulates increased secretion of the protective mucus that lines the gastrointestinal tract and increases mucosal blood flow, thereby increasing mucosal integrity. It is sometimes co-prescribed with non-steroidal anti-inflammatory drugs (NSAIDs) to prevent the occurrence of gastric ulceration, a common adverse effect of the NSAIDs.

Interestingly, although not licensed for the indication, misoprostol is commonly prescribed to expedite pregnancy by causing uterine contractions and the ripening (opening) of the cervix. The drug is highly effective, although high doses can cause fetal death and uterine rupture.

More recently, misoprostol has been increasingly used for early termination of pregnancy (see abortion). It is used in conjunction with mifepristone (RU-486). After mifepristone is taken orally, misoprostol is taken 24-72 hours later causing the expulsion of the fetus and associated matter within four hours.

In countries where abortion is illegal, misoprostol is commonly being used to cause an abortion without medical supervision. This method is especially common in South American countries where misoprostol is avilable from pharmacies for other medical indications.

More common adverse effects of misopristol include nausea, vomiting, diarrhea, abdominal pain, chills, shivering and fever.