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Enzyme-inducing antiepileptic and contraception — GPhC CRA MCQ

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HardCNS TherapeuticsEnzyme-inducing antiepileptic and contraceptionGPhC CRA

A 28-year-old woman with epilepsy asks about a new prescription for combined oral contraception. She takes carbamazepine 400mg twice daily and has had breakthrough seizures when doses were missed. What is the most appropriate alternative?

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Correct answer: B — Recommend prescriber review for a method unaffected by enzyme induction such as copper IUD or depot injection

Carbamazepine is a strong enzyme inducer and can reduce the effectiveness of combined hormonal contraception. A contraceptive method not affected by enzyme induction, such as copper IUD or depot medroxyprogesterone, should be discussed with an appropriate clinician. Timing separation does not overcome enzyme induction. Pharmacists should not switch antiepileptic therapy, and valproate has major teratogenic restrictions.

Reference: BNF; FSRH guidance