A 24-year-old nulliparous woman presents 96 hours after unprotected intercourse with a request for emergency contraception. She has no medical comorbidities and is not on any regular medications. Her last menstrual period was 10 days ago, placing her in the fertile window. Which agent should be offered, and what is the rationale?

Explanation

## Emergency Contraception Beyond 72 Hours: Ulipristal Acetate **Key Point:** Levonorgestrel efficacy drops sharply after 72 hours. For patients presenting 72–120 hours post-intercourse, ulipristal acetate (a selective progesterone receptor modulator) is the preferred agent due to superior efficacy in this extended window. ### Comparative Efficacy by Time Window | Timepoint | Levonorgestrel | Ulipristal Acetate | Clinical Implication | |-----------|----------------|--------------------|----------------------| | **0–24 hours** | 95% | 98% | Both excellent; levonorgestrel preferred (cost/access) | | **24–72 hours** | 60–85% (declining) | 85–95% | Ulipristal superior; consider if available | | **72–120 hours** | <30% (ineffective) | 65–95% | **Ulipristal is standard of care** | | **>120 hours** | Not recommended | Not recommended | Copper IUD only option | **High-Yield:** At 96 hours (4 days), the patient is BEYOND the effective window for levonorgestrel but WITHIN the optimal window for ulipristal acetate. This is a classic NEET PG discriminator question. ### Mechanism: Why Ulipristal Works Longer 1. **Levonorgestrel:** Progestin agonist; works by inhibiting LH surge. Efficacy depends on timing relative to ovulation; loses effectiveness as ovulation approaches or occurs. 2. **Ulipristal Acetate:** Selective progesterone receptor modulator (SPRM); can delay follicular rupture even if LH surge has begun. Maintains efficacy over a longer window. **Clinical Pearl:** Ulipristal acetate can inhibit ovulation even after the LH surge has started, whereas levonorgestrel cannot. This explains its extended therapeutic window. ### Dosing & Administration - **Ulipristal acetate:** 30 mg as a single oral dose - **Timing:** Most effective if given within 120 hours; can be considered up to 5 days post-intercourse - **Availability:** Available in India through specialized pharmacies; more expensive than levonorgestrel **Warning:** Do NOT confuse ulipristal acetate (emergency contraceptive) with mifepristone (abortifacient). Ulipristal is a contraceptive; mifepristone terminates pregnancy. ### Why Not Copper IUD at 96 Hours? While the copper IUD is highly effective (>99%) and can be inserted up to 5 days post-intercourse, it is invasive and not first-line for a nulliparous woman without prior IUD use. Oral ulipristal acetate is less invasive and equally effective in this timeframe. **Mnemonic:** **ULIP-RISTA** = **ULtra-extended window, Inhibits LH even Post-surge, Receptor modulator, Selective, Timed for 72–120 hours, Acetate formulation** [cite:Park 26e Ch 8; WHO Emergency Contraception Guideline 2023]