skip to main content

Topiramate-COC interaction — GPhC CRA MCQ

Instant feedback + full explanation. One question, done properly.

HardDrug InteractionsTopiramate-COC interactionGPhC CRA

A 19-year-old woman presents with a prescription for topiramate 25 mg once daily for migraine prophylaxis. She mentions she is taking a combined oral contraceptive pill (ethinylestradiol/levonorgestrel). What is the most important interaction to flag?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Topiramate at doses of 200 mg or more per day can reduce the efficacy of hormonal contraception, but doses below this are unlikely to interact

Topiramate is an enzyme inducer at doses of 200 mg per day or above, which can reduce the efficacy of combined oral contraceptives. At the prescribed dose of 25 mg daily (migraine prophylaxis doses are typically 50-100 mg daily), the interaction is less likely to be clinically significant. However, if the dose is increased above 200 mg, alternative or additional contraception would be needed. The prescriber and patient should be aware of this dose-dependent interaction.

Reference: BNF; FSRH Guideline Drug Interactions with Hormonal Contraception