A 28-year-old unmarried woman presents to the emergency department 18 hours after unprotected intercourse with her partner. She has a regular 28-day menstrual cycle and is currently in her follicular phase (day 8 of cycle). She is otherwise healthy with no contraindications to hormonal contraception. On examination, she is hemodynamically stable. What is the most appropriate emergency contraceptive regimen for this patient?

Explanation

## Emergency Contraception: Timing and Method Selection **Key Point:** Levonorgestrel 1.5 mg as a single oral dose is the **most appropriate first-line emergency contraceptive** for this patient, who presents at 18 hours after unprotected intercourse — well within the optimal 72-hour window. ### Mechanism of Action Levonorgestrel (LNG) works primarily by: 1. **Inhibiting or delaying ovulation** — the dominant mechanism, especially effective in the follicular phase 2. Altering cervical mucus viscosity, impeding sperm transport 3. Possible alteration of endometrial receptivity 4. **Does NOT interrupt an established pregnancy** (not abortifacient) ### Efficacy by Timing (WHO data) | Time Since Intercourse | Pregnancy Prevention Efficacy | |---|---| | 0–24 hours | ~95% | | 24–48 hours | ~85% | | 48–72 hours | ~58% | | 72–120 hours | Reduced but still recommended | **High-Yield:** This patient is on **day 8** of a 28-day cycle (follicular phase, approaching fertile window). LNG is maximally effective when administered before the LH surge/ovulation — making early administration in the follicular phase particularly impactful. ### Why Levonorgestrel Over Alternatives? - **Option B (Yuzpe regimen):** Combined OCP regimen (ethinyl estradiol + LNG) is an older, less preferred method with more side effects (nausea, vomiting ~50%) and lower efficacy compared to LNG alone. It is a second-line option when LNG is unavailable. - **Option C (Mifepristone 10 mg for 3 days):** Mifepristone at low doses has been studied as EC in some countries, but the standard regimen described here (10 mg × 3 days) is **not a recognized emergency contraceptive protocol**. High-dose mifepristone (600 mg) is used for medical abortion post-implantation. This option is pharmacologically inaccurate as stated. - **Option D (Copper IUD):** The copper IUD is indeed the **most effective** single method of EC (>99% efficacy up to 5 days), but it requires a trained provider, pelvic examination, and insertion procedure. For an otherwise healthy woman presenting at 18 hours with no contraindications to hormonal EC, **oral LNG is the most appropriate first-line choice** per WHO, FOGSI, and Indian National Guidelines — being non-invasive, widely available, and highly effective at this early time point. **Clinical Pearl (KD Tripathi / FOGSI Guidelines):** Levonorgestrel 1.5 mg single dose is the WHO-recommended first-line emergency contraceptive. It is preferred over the Yuzpe regimen due to superior efficacy and tolerability. Copper IUD, while more effective overall, is reserved for patients who also desire ongoing contraception or when hormonal methods are contraindicated. **Standard Pharmacology Note:** LNG-EC acts as a progestin agonist at hypothalamic-pituitary level to suppress the LH surge, thereby preventing follicular rupture. It has no effect on an already-implanted embryo and is not classified as an abortifacient. [cite: KD Tripathi Essentials of Medical Pharmacology 8e, Ch 23; WHO Medical Eligibility Criteria for Contraceptive Use 5e; Park's Textbook of Preventive and Social Medicine 26e Ch 10]