Antiprogesterone activity of RU 486 and its contragestive and other applications.

RU 486 is the first antiprogesterone to be used clinically. It inhibits the action of the hormone at the receptor level in target tissues. Its action is particularly significant in the endometrium where it prevents the initiation and progression of pregnancy in the first weeks (contragestive effect). The data indicate that the compound can be used for: voluntary interruption of pregnancy between 6 and 10 weeks; induction of menstruation during the fifth week of amenorrhoea, and post-coital contraception. Current trials include its use as a once-a-month menses inducer. It can also be utilized for therapeutic interruption at a late stage of pregnancy, and tried as adjuvant treatment in some cases of breast cancer. The data on RU 486 have been obtained through studies in physio-pharmacological endocrinology and biochemistry. The development of this antihormone represents a concerted research link between biology and medicine.