A 28-year-old unmarried woman presents to the emergency department 18 hours after unprotected sexual intercourse with her boyfriend. She is anxious and requests emergency contraception. Her last menstrual period was 10 days ago. She has no contraindications to hormonal methods. On examination, vital signs are stable and abdomen is soft. What is the most appropriate emergency contraceptive regimen for this patient?

Explanation

## Emergency Contraception: Levonorgestrel as First-Line ### Clinical Context This patient presents within the critical 72-hour window for emergency contraception. She is at low risk of pregnancy (only 10 days post-menses), has no contraindications, and seeks a simple, accessible method. ### Levonorgestrel: The Gold Standard **Key Point:** Levonorgestrel 1.5 mg as a single oral dose is the WHO-recommended, most effective, and most accessible emergency contraceptive for use within 72 hours of unprotected intercourse. **High-Yield:** - **Efficacy:** 60–90% effective if taken within 72 hours; most effective in first 24 hours - **Mechanism:** Inhibits or delays ovulation; does NOT work if ovulation has already occurred - **Dosing:** Single 1.5 mg dose (or 0.75 mg × 2 doses 12 hours apart — equivalent efficacy) - **Timing:** Efficacy decreases with time; ideally given within 24 hours, but acceptable up to 72 hours - **Safety:** Well-tolerated, minimal side effects (nausea, fatigue, headache); no absolute contraindications ### Comparison of Emergency Contraceptive Methods | Method | Timing | Efficacy | Mechanism | Notes | |--------|--------|----------|-----------|-------| | **Levonorgestrel** | Within 72 hrs | 60–90% | Ovulation inhibition | First-line, OTC in many countries | | **Ulipristal acetate** | Within 120 hrs | 95%+ | Selective progesterone receptor modulator | More effective, especially days 3–5; prescription only | | **Copper IUD** | Within 5 days | >99% | Spermicide + endometrial toxicity | Most effective; invasive; requires insertion | | **Yuzpe regimen** | Within 72 hrs | 50–80% | Combined estrogen + progestin | Outdated; more side effects; rarely used now | | **Mifepristone** | Within 72 hrs | 85%+ | Progesterone antagonist | Abortifacient; restricted in many countries; not first-line | **Clinical Pearl:** Levonorgestrel works best when given before the LH surge (which triggers ovulation). Once ovulation has begun, it is ineffective. This is why earlier administration is more effective. ### Why This Patient Gets Levonorgestrel - Within 72-hour window ✓ - No contraindications ✓ - Accessible, affordable, no prescription needed in many settings ✓ - Adequate efficacy for this early post-menses timing ✓ [cite:Park 26e Ch 10]