Mifepristone is a synthetic steroid, it is used medically in humans as an abortifacient, for the chemical termination of early pregnancy. In the U.S it is made by Danco Laboratories under the tradename Mifeprex. During early trials it was known as RU-486.
It is used in the termination of pregnancy under fifty days from conception. A typical dose is 600 mg orally then either a further 400 mg or an oral prostaglandin analogue after a further 48 hours. It is between 92% and 99% effective, depending on the trial data examined, within four hours of the second dosing. As a stand-alone agent it is around 80% effective.
It works by a competative interaction with both endogenous and exogenous progesterone at receptor sites. It also has slight antiglucocorticoid and antiandrogenic effects in larger doses.
It is a white powder, highly soluble in methanol and only poorly soluble in water, its structural name is 11β-[p-(Dimethylamino)phenyl]-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one. Empirically it is C29H35NO2
It is contraindicated in cases of ectopic pregnancy, adrenal failure, hemorrhagic disorders, anticoagulant or corticosteroid therapy. Side effects include an expected amount of abdominal pain and vaginal bleeding, also there can be nausea, vomiting and fever. Incomplete termination would require further intervention, such as vacuum aspiration.
The compound was discovered by researchers at Roussel Uclaf in 1980 while studying glucocorticoid receptor antagonists. Clinical testing began in 1982. It was first licensed in France in 1988, for use in combination with prostaglandin. Then on October 26 of that year Roussel Uclaf stated that it would abandon distribution of the drug but bowed to pressure from the government of France two days later to resume distribution. It was approved in a number of other European countries in the 1990s, for example the United Kingdom approved its use in 1991.
It was only approved by the U.S. Food and Drug Administration (FDA) in September 2000. Early research was difficult as Roussel Uclaf did not seek U.S. approval and it was further interrupted when the Bush administration banned the importation of mifepristone in 1989. This ban was not reversed until 1993. In 1994 Roussel Uclaf gifted the U.S. rights to the Population Council and the drug was on approvable status from 1996. Production was intended to begin through the Danco Group in 1996 but they withdrew briefly in 1997, retarding availability again.
Mifepristone has been investigated in the treatment of Cushing's syndrome and a number of cancers.