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Carbamazepine and contraception — GPhC CRA MCQ

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ModerateCNS TherapeuticsCarbamazepine and contraceptionGPhC CRA

A 22-year-old woman taking carbamazepine for focal seizures asks for emergency contraception after unprotected sex 36 hours ago. She uses a combined oral contraceptive and missed two tablets last week. She weighs 74kg and has no copper intrauterine device fitted. What is the most important interaction to flag?

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Correct answer: A — Carbamazepine reduces effectiveness of oral hormonal contraception

Carbamazepine is an enzyme inducer and can reduce the effectiveness of combined oral contraception and oral emergency contraception. A copper intrauterine device is the most effective emergency contraceptive option and is not affected by enzyme induction. If oral emergency contraception is used, specialist guidance on choice and dose is needed. The interaction should be flagged urgently because timing matters.

Reference: BNF; Faculty of Sexual and Reproductive Healthcare guidance