Emergency contraceptive drugs are:
**Core Concept**
Emergency contraception refers to the use of medications or devices to prevent pregnancy after unprotected sex or contraceptive failure. The primary goal is to inhibit or delay ovulation, prevent fertilization, or interfere with implantation.
**Why the Correct Answer is Right**
Emergency contraceptive drugs work through various mechanisms to prevent pregnancy. Levo-norgestrel (A), a progestin-only pill, primarily inhibits ovulation by suppressing the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn reduces the secretion of luteinizing hormone (LH) from the anterior pituitary gland. LH is essential for ovulation, and its suppression prevents the rupture of the follicle and subsequent release of an egg. Estrogen + progesterone (B) combinations, such as Yuzpe regimen, also work by delaying ovulation and possibly altering the cervical mucus to prevent sperm penetration. Mifepristone (C), a progesterone receptor antagonist, blocks the action of progesterone, which is essential for the preparation of the uterine lining for implantation. By preventing progesterone's action, mifepristone may prevent implantation or disrupt early embryonic development.
**Why Each Wrong Option is Incorrect**
**Option A:** While levo-norgestrel is indeed an emergency contraceptive drug, the other options are also valid, making this choice incomplete.
**Option B:** Although estrogen + progesterone combinations can be used for emergency contraception, they are not the only options available.
**Option C:** Mifepristone is a valid emergency contraceptive drug, but the question asks for all options, and this choice does not encompass the full range of available medications.
**Clinical Pearl / High-Yield Fact**
It is essential to note that emergency contraception is most effective when used within 72 hours after unprotected sex. The effectiveness of these medications decreases with time, making prompt action crucial in preventing pregnancy.
**Correct Answer Line**
✓ Correct Answer: D. All of the above