RU-486, also known as mifepristone, is only one drug that when used with misoprostol, a prostaglandin, can end a pregnancy without surgery. Walker said a prostaglandin is a drug that causes the uterus to contract and end the pregnancy. She said the regimen works only during the first seven weeks of pregnancy or 49 days after a woman's last menstrual period. According to the FDA, mifepristone, an antiprogesterone drug, is only distributed to physicians who can accurately determine the duration of a patient's pregnancy. An antiprogesterone is a drug that shuts off the development of the hormone progesterone.
Progesterone is essential for establishing and maintaining a pregnancy.
Mifepristone stops the early pregnancy from growing, Walker said. An additional component involves a requirement that a physician must be able to detect ectopic or tubal pregnancies. The FDA defines an ectopic pregnancy as a condition when the fertilized egg grows in one of the fallopian tubes. The fallopian tubes connect the ovaries to the uterus. According to Planned Parenthood, the medical abortion is similar to an early miscarriage.