**Question:** The most appropriate drug for emergency contraception is:

A. Levonorgestrel (Plan B)
B. Ethinyl estradiol and levonorgestrel (Yuzpe regimen)
C. Oral contraceptive pills
D. Hormonal intrauterine device (IUD)

**Core Concept:** Emergency contraception refers to the use of hormonal or mechanical methods to prevent pregnancy following unprotected sex or contraceptive failure. The goal is to block fertilization or implantation.

**Why the Correct Answer is Right:** Levonorgestrel (Plan B) is the most appropriate drug for emergency contraception because it is a progestogen-only contraceptive that primarily inhibits ovulation. When taken within 120 hours (5 days) after unprotected intercourse, it can reduce the risk of pregnancy by up to 85%.

**Why Each Wrong Option is Incorrect:**

A. Oral contraceptive pills (C) are not recommended for emergency contraception because they contain both estrogen and progestogen, which may cause side effects and reduce their efficacy when taken outside their typical usage window.

B. The Yuzpe regimen (Yuzpe regimen) involves a combination of ethinyl estradiol and levonorgestrel. While it is an effective emergency contraceptive method, it has been superseded by levonorgestrel-only pills like Plan B due to better tolerability and safety profile.

D. Hormonal intrauterine devices (IUD) are mechanical methods for emergency contraception, not hormonal. They work by releasing copper ions or releasing levonorgestrel, preventing sperm from fertilizing an egg or implanting a fertilized egg in the uterine lining. However, they are not suitable for all patients and require insertion within 5 days after unprotected intercourse.

**Clinical Pearl:** Plan B (levonorgestrel) provides a more effective and safer alternative to the Yuzpe regimen, and is suitable for a broader range of patients. As an emergency contraceptive, it can be prescribed up to 5 days after unprotected intercourse, making it the most appropriate choice among the given options.