Common abortifacients are mifepristone and misoprostol. In addition, there are several herbal mixtures with abortifacient claims, however there is no available data on the efficacy of these plants in humans.
Misoprostol, a synthetic prostaglandin E1 (PGE1) analogue, was first approved in 1988 under the trade name Cytotec for reducing the risk of NSAID-induced gastric ulcers. 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.
Misoprostol alone is sometimes used for self-induced abortion in Latin American countries where legal abortion is not available, and by some people in the United States who cannot afford a legal abortion.
Some substances might prevent implantation and thus destroy the blastocyst, although their known primary effect is to prevent fertilization. The existence of these post-fertilization mechanisms is debated. There is controversy as to whether pregnancy begins at the moment of fertilization, or at the moment the blastocyst implants in the uterine lining. American federal law and British law mark the beginning of pregnancy at implantation; thus, even if post-fertilization mechanisms were proven, these substances would still be labeled as contraceptives, rather than abortifacients.
The following birth control methods have been proposed to sometimes prevent implantation of a blastocyst, although (except as noted) they primarily work by preventing fertilization:
Although not substances, and therefore not technically abortifacients, the following techniques have also been proposed to sometimes prevent implantation of a blastocyst:
The ancient Greek colony of Cyrene at one time had an economy based almost entirely on the production and export of silphium, a powerful abortifacient in the parsley family. Silphium figured so prominently in the wealth of Cyrene that the plant appeared on the obverse and reverse of coins minted there. Silphium, which was native only to that part of Libya, was overharvested by the Greeks and was effectively driven to extinction. The standard theory, however, has been challenged by a whole spectrum of alternatives (from an extinction due to climate factors, to the so-coveted product being in fact a recipe made of a composite of herbs, attribution to a single species meant perhaps as a disinformation attempt).
As Christianity and in particular the institution of the Catholic Church increasingly influenced European society, those who dispensed abortifacient herbs found themselves classified as witches and were often persecuted (see witch-hunt).