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VPA-LTG Interaction — SCE Neurology MCQ

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HardEpilepsy & Seizure DisordersVPA-LTG InteractionSCE Neurology

Valproate is added to lamotrigine. What pharmacokinetic interaction?

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

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Correct answer: DVPA inhibits LTG glucuronidation, doubling LTG levels — halve LTG dose

The best answer is “VPA inhibits LTG glucuronidation, doubling LTG levels — halve LTG dose”. NICE bases epilepsy diagnosis and treatment on seizure type, syndrome, recurrence risk, comorbidity, pregnancy potential and medicine harms; typical provoked seizures are managed by correcting the provoking cause. The alternatives “None, within the relevant UK pathway, after excluding important mimics”, “VPA reduces LTG levels, after excluding important mimics, after specialist assessment”, “LTG increases VPA levels, after specialist assessment, when the phenotype supports it”, “at high doses, when the phenotype supports it, within the relevant UK pathway” are clinically adjacent possibilities, but they do not match the defining chronology, localisation, physiology, investigation result or UK management sequence in this stem.

Reference: NICE NG217 epilepsy recommendations: https://www.nice.org.uk/guidance/ng217/chapter/Recommendations