RU-486 is the name commonly used for an artificial steroid that blocks progesterone, a hormone needed to continue a pregnancy.2

Other names for RU-486:
is the generic name for RU-486. In the U.S., RU-486 is sold under the brand names Mifeprex and Early Option.

Note: An RU-486 abortion involves two drugs
When taken alone, RU-486 causes a complete abortion only about 60% of the time.3 A second drug, a prostaglandin, is given 48 hours later to increase its effectiveness. The prostaglandin causes uterine contractions to help expel the embryo.

Misoprostol (brand name Cytotec) is the prostaglandin used with RU-486 in the U.S.
Important Notice: The manufacturer of Cytotec (misoprostol) has warned doctors that it recommends this drug not be used for abortion.

2 I. Spitz et al., "Early pregnancy termination with mifepristone and misoprostol in the United States," New England Journal of Medicine 1998, 338:1241-47.

3 Ibid.; L. Birgerson and V. Odlind, "Early pregnancy termination with anti-progestins: a comparative clinical study of RU-486 given in two dose regimens and Epostane," Fertil. Steril. 48:565-70 (1987).