Mifepristone is an antiprogestin; that is, it blocks the action of progesterone, a naturally produced hormone that prepares the inner lining of the uterus for implantation of a fertilized ovum and support of a growing embryo and placenta. The drug is taken orally in a prescribed dose during the first seven to nine weeks of pregnancy, and within two days the uterine lining begins to deteriorate, usually causing bleeding similar to that experienced during normal menstruation. The Mifepristone is then followed up by a dose (taken orally or as a vaginal suppository) of the synthetic prostaglandin, which stimulates the uterus to undergo contractions. The embryo and other uterine contents are expelled in a process very similar to spontaneous abortion or miscarriage.
Misoprostol is a synthetic prostaglandin E1 analogue that has uterine contractibility properties. Misoprostol interact with specific receptors on myometrial cells causes myometrial contraction thus soften & open the cervix resulting in the expulsion of uterine contents.