abortifacient
abortifacient, any drug or other chemical preparation or substance that is used to intentionally induce abortion.
Historical preparations
For centuries, herbal abortifacients have been made from infusions or oils of plants such as pennyroyal (Mentha pulegium), angelica (Angelica species), and tansy (Tanacetum vulgare). Such preparations are no more likely to terminate a pregnancy than they are to induce potentially lethal reactions such as vomiting, hemorrhages, and convulsions in the women who take them. Truly effective abortifacients were not developed until the end of the 20th century, when the biochemical processes behind cell division and growth and the role of hormones in reproductive processes were understood.
Modern agents
The most common agent used in modern medication abortion is mifepristone (also known as RU-486), a steroid that is given during the early weeks of pregnancy in conjunction with the synthetic prostaglandin misoprostol. Misoprostol, administered in prescribed doses either orally or as a vaginal suppository, causes the uterus to contract much as it would at the beginning of labor or during a miscarriage. Taken alone, it is rarely sufficient to expel the embryo and placenta from the uterus, but it is very effective as a sequel to treatment with mifepristone.
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Mifepristone works by competing with progesterone for receptors on cells. By occupying receptor binding sites, it prevents the hormone from stimulating the inner lining of the uterus to prepare for implantation by a fertilized ovum. When administered early in pregnancy, mifepristone causes the breakdown of the uterine lining; a follow-up dose of misoprostol induces expulsion of the embryo and other uterine contents.
The antimetabolite methotrexate was once commonly used for medication abortion, though it is now rarely employed. It historically was administered by injection and worked by blocking the rapid cell division characteristic of embryonic and placental growth. Similar to mifepristone, it was combined with misoprostol to complete the abortion. Full abortion with methotrexate often took weeks instead of days, as with mifepristone, and women were prone to more adverse effects.
Side effects
Modern agents used in medication abortion can cause physical side effects similar to heavy menstruation or miscarriage, with significant bleeding and cramping. Gastrointestinal issues, such as nausea and diarrhea, are also common. More serious complications are infrequent. With mifepristone, potentially dangerous side effects include severe bleeding and incomplete abortion, which can lead to infection and must be resolved through surgery.