A 29-year-old woman on carbamazepine requests emergency contraception 4 days after unprotected sex. What is the most appropriate action?

• A. Offer LNG-EC only
• B. Offer Ulipristal acetate
• C. Refer for copper intrauterine device
• D. No action needed

Answer: (C)

Enzyme-inducing anticonvulsants like carbamazepine can speed up the metabolism of hormonal emergency contraception, making it less reliable. This matters here because four days have passed since unprotected sex, so a LNG-based option would be outside its usual effective window and even ulipristal—or its effectiveness—can be diminished by the drug interaction.

The copper intrauterine device is not affected by hepatic enzyme induction and remains highly effective as emergency contraception when inserted within about five days of intercourse. It also offers ongoing contraception thereafter. For a patient on carbamazepine presenting four days after unprotected sex, referring for copper IUD insertion is the best course.