Abortifacients

An abortifacient ("that which will cause a miscarriage" from Latin: "miscarriage" and "making") is a substance that induces abortion. Abortifacients for animals that have mated undesirably are known as mismating shots.

Common abortifacients used in performing medical abortions include mifepristone, which is typically used in conjunction with misoprostol in a two-step approach. is commonly used to induce abortion in the second or third trimester. There are also several herbal mixtures with abortifacient claims, though there are no available data on the efficacy of these plants in humans.

Prostaglandin analogues, such as misoprostol or gemeprost (both synthetic prostaglandin E₁ (PGE₁) analogues), are often used to terminate pregnancy up to 24 or 60 days of gestation, in combination with mifepristone (a progesterone receptor antagonist) or methotrexate (an antifolate). Misoprostol administered vaginally is more effective than when administered orally. Misoprostol is approved in France under the trade name GyMiso for use with mifepristone for medical abortion. Misoprostol is used off-label with mifepristone for medical abortion in the U.S. Dinoprostone, given by the extra-amniotic route, can be used for late abortion (second trimester).

Mifepristone is a progesterone receptor antagonist also known as RU-486. It is marketed under the trade name Mifegyne in France and countries other than the U.S., and under the trade name Mifeprex in the U.S. It is used in conjunction with a prostaglandin analogue.

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