A medical abortion uses medication to end a pregnancy. This can be accomplished by taking a series of pills. The alternative to medical abortion is surgical abortion, which terminates a pregnancy by emptying the uterus with special instruments.
The abortion pill -- RU486 (brand name Mifeprex) is usually used for a medical abortion. The abortion pill contains the synthetic steroid mifepristone, which blocks your body's progesterone (the hormone necessary to sustain pregnancy). Forty-eight hours after you have taken Mifeprex, you will return to your doctor's office and receive a dose of a second medication, misoprostol.
Medical abortion can be performed as soon as a pregnancy is confirmed. It is FDA-approved for use up to 49 days after the first day of your last menstrual period or if you are 7 weeks pregnant (which equals 5 weeks since conception). Please be aware that a medical abortion is not FDA-approved if it has been more than 49 days since the start of your last menstrual period; some healthcare providers will still use this method after this point (usually up to 63 days/9 weeks pregnant), but doing so is considered "off label" (meaning, no longer FDA-approved).
A medical abortion is 92%-98% effective, allowing a woman to completely pass the pregnancy without the use of surgery. It may take anywhere from about a day to 3-4 weeks from the time you take the first medication until the medical abortion is completed. When taken alone, the abortion pill, mifepristone, causes a complete abortion about 64%-85% of the time. When misoprostol is given 48 hours later, medical abortion effectiveness is increased to 92%-98%.A medical abortion is an option to terminate a pregnancy that is under 7 weeks.
Source:
Spitz, I.M., Bardin, C.W., Benton, L. & Robbins, A. (1998). Early pregnancy termination with mifepristone and misoprostol in the United States. New England Journal of Medicine, 338(18):1241-47. Accessed through private subscription April 2011.

