Levonorgestrel Emergency Contraceptive Pill (LNG-ECP, 1.5 mg single dose) is most effective if taken within what time frame after unprotected sexual intercourse?
- A Within 72 hours, with effectiveness declining over time ✓
- B Within 24 hours (effectiveness ~95%)
- C Within 120 hours with uniform effectiveness throughout
- D Within 7 days — same as copper IUD as emergency contraception
Correct answer: A. Within 72 hours, with effectiveness declining over time
Explanation
LNG-ECP is most effective within 72 hours of unprotected intercourse, with effectiveness declining with time: ~95% if taken within 24 hours, ~85% within 48 hours, ~58% within 72 hours. It can be used up to 120 hours but with significantly reduced efficacy. The copper IUD, however, can be inserted up to 120 hours (5 days) after unprotected intercourse with >99% efficacy. LNG works primarily by delaying/inhibiting ovulation.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.