RU-486 is the code name for an abortion drug that is now widely known as Mifepristone. This drug was developed in France and has been shown to be highly effective in inducing spontaneous abortion when administered in early pregnancy. Mifepristone has also been demonstrated to be highly effective as a post-coital contraceptive (morning after pill) when administered within 72 hours after unprotected intercourse. Additional studies have shown the drug has the potential for preventing implantation and inducing menstruation when administered in the last half of the menstrual cycle.