Final answer:
Mifepristone (RU-486) is a medication used to terminate early pregnancies by blocking progesterone, a necessary hormone for sustaining pregnancy. It should be distinguished from emergency contraceptives and IUDs such as Mirena. The availability of mifepristone is subject to varying legal regulations.
Step-by-step explanation:
Mifepristone (RU-486) is a medication that is used for the voluntary termination of an existing pregnancy, a process also referred to as an abortion. Mifepristone works by blocking the hormone progesterone, which is needed to sustain a pregnancy. Without progesterone, the lining of the uterus breaks down, and the pregnancy cannot continue. Mifepristone is often used in combination with another medication, misoprostol, to complete the abortion process. It's important to make a distinction between mifepristone and emergency contraception, such as Plan B One-Step (the 'morning after pill'), which is intended to prevent pregnancy after unprotected intercourse and before a pregnancy is established. Emergency contraceptives are not the same as abortion pills and should not be confused with intrauterine devices (IUDs) like Mirena, which can also prevent pregnancies but are meant for longer-term birth control. Variations in laws regarding abortion can greatly affect the availability and legal use of mifepristone, as different places have varying regulations that might consider factors such as fetal viability, which is the ability of a fetus to survive outside the womb. This medication is taken under medical supervision, and its administration is subject to the regulatory framework of the region in which it's used.