Drugs used in emergency contraception :
**Core Concept**
Emergency contraception is a method of preventing pregnancy after unprotected sex or when a regular contraceptive method fails. It works by preventing or delaying ovulation, fertilization, or implantation of a fertilized egg in the uterus. The drugs used in emergency contraception have different mechanisms of action, including inhibition of ovulation and alteration of the endometrium.
**Why the Correct Answer is Right**
The most commonly used emergency contraceptive pills (ECPs) are levonorgestrel (Plan B) and ulipristal acetate (Ella). Levonorgestrel is a progestin that inhibits ovulation by suppressing the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, leading to a decrease in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. This prevents the rupture of the ovarian follicle and subsequent ovulation. Ulipristal acetate, on the other hand, is a selective progesterone receptor modulator (SPRM) that alters the endometrium, making it less receptive to implantation of a fertilized egg.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a known emergency contraceptive drug. Many drugs have not been proven to be effective in preventing pregnancy after unprotected sex.
**Option B:** This option is incorrect because it is not a commonly used emergency contraceptive drug. While it may have some effect on preventing pregnancy, it is not a recommended option for emergency contraception.
**Option C:** This option is incorrect because it is a common contraceptive pill, but it is not typically used for emergency contraception. It works by preventing ovulation, but it is not as effective as levonorgestrel or ulipristal acetate in preventing pregnancy after unprotected sex.
**Clinical Pearl / High-Yield Fact**
It is essential to note that emergency contraception is most effective when taken within 72 hours after unprotected sex. Levonorgestrel and ulipristal acetate can be taken up to 120 hours after unprotected sex, but their effectiveness decreases with time. Additionally, emergency contraception is not a substitute for regular contraception and should not be used as a primary method of preventing pregnancy.
**Correct Answer: B. Ulipristal acetate**