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AED Cross-Reactivity – Aromatic Anticonvulsants — SCE Neurology MCQ

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ModerateEpilepsy & Seizure DisordersAED Cross-Reactivity – Aromatic AnticonvulsantsSCE Neurology

A 40-year-old woman with known epilepsy on carbamazepine presents with a maculopapular rash, fever, lymphadenopathy, and eosinophilia 4 weeks after a dose increase. Her neurologist suspects carbamazepine hypersensitivity. She needs an alternative AED. What is the cross-reactivity risk between carbamazepine and other aromatic AEDs?

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Correct answer: A — There is approximately 25–30% cross-reactivity between carbamazepine, phenytoin, oxcarbazepine, and lamotrigine for hypersensitivity reactions — these should be avoided or introduced with extreme caution

Aromatic AEDs (carbamazepine, phenytoin, phenobarbital, oxcarbazepine, lamotrigine) share structural similarities and have approximately 25–30% cross-reactivity for hypersensitivity reactions (SJS/TEN, DRESS). If a patient has a hypersensitivity reaction to one aromatic AED, all others in the group should be avoided or used with extreme caution. Non-aromatic alternatives include levetiracetam, sodium valproate, gabapentin, pregabalin, and lacosamide. A: Cross-reactivity is well-documented. C: Multiple aromatic AEDs cross-react. D: Cross-reactivity is between aromatic AEDs. E: Lamotrigine has cross-reactivity risk.

Reference: BNF – AED Hypersensitivity; NICE NG217 (2025)