Antiprogestin used for emergency contraception is:
## **Core Concept**
The question tests knowledge of emergency contraception and the role of antiprogestins in this context. Emergency contraception is a method used to prevent pregnancy after unprotected sex or contraceptive failure. Antiprogestins, also known as progesterone receptor antagonists, are a class of drugs that can interfere with the action of progesterone, a hormone essential for maintaining pregnancy.
## **Why the Correct Answer is Right**
Mifepristone (also known as RU486) is a well-known antiprogestin that works by blocking the progesterone receptor. This action prevents the implantation of a fertilized egg into the uterine lining or disrupts an early pregnancy. Mifepristone has been used for medical abortion and, at a lower dose, for emergency contraception. Its effectiveness in emergency contraception makes it a correct choice for this purpose.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain prostaglandins and their analogs are used in obstetrics for labor induction and abortion, they are not classified as antiprogestins and are not used for emergency contraception in the same way antiprogestins are.
- **Option B:** This option is not specified, but based on the context, any other option not directly related to antiprogestin action or not known for emergency contraception would be incorrect.
- **Option D:** Similarly, without a specific drug mentioned, any drug not recognized as an antiprogestin or not used for emergency contraception would be incorrect.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that mifepristone, when used for emergency contraception, is most effective when taken as soon as possible after unprotected sex, ideally within 72 hours. It works by preventing ovulation, fertilization, or implantation of a fertilized egg. A notable clinical consideration is that mifepristone can also be used in medical abortion up to 10 weeks of gestation, showcasing its role in reproductive health beyond emergency contraception.
## **Correct Answer:** . Mifepristone