Mifepristone: current knowledge and emerging prospects.

The first clinically available antiprogestin, mifepristone has generated immense interest in the research community since its' discovery in 1980. Mifepristone is a synthetic orally active steroid with potent antiglucocorticoid, antiprogestogen and a weak anti-androgen activity, used primarily for termination of pregnancy. It acts as a competitive receptor antagonist at the progesterone receptor in the presence of progesterone, and acts as a partial agonist in the absence of progesterone.