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ET – MRgFUS Thalamotomy — SCE Neurology MCQ

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HardMovement DisordersET – MRgFUS ThalamotomySCE Neurology

A patient with Lennox–Gastaut syndrome becomes markedly somnolent after cannabidiol is added to stable clobazam. Seizures have improved and liver tests are normal. Which pharmacokinetic response is most appropriate?

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

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Correct answer: A — Reduce clobazam because cannabidiol raises N-desmethylclobazam via CYP2C19 inhibition

Explanation lettering: D = shown as A · C = shown as B · E = shown as C · B = shown as D · A = shown as E

A misstates the dominant interaction and does not target the accumulating sedative metabolite. B is wrong: the important valproate interaction is hepatotoxicity risk rather than a simple doubling of valproate exposure. C ignores proven combination efficacy. D is correct: cannabidiol inhibits CYP2C19, increasing N-desmethylclobazam three- to four-fold; clobazam reduction should be considered when sedation occurs. E reverses both the enzyme effect and clinical response.

Reference: Epidyolex cannabidiol Summary of Product Characteristics: https://www.medicines.org.uk/emc/product/10781/smpc