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Topiramate-valproate-induced hyperammonemic encephalopathy syndrome: Case report

By CW Fung, V Wong and E Cheung


A 15-year-old boy with inverted duplication of chromosome 15 was admitted for acute onset of irritability, increasing sleepiness, and worsening of seizures. He had been on valproate and other anticonvulsants. However, he was found to have hyperammonemia within 2 weeks after the addition of low-dose topiramate to valproate. He recovered within 7 days after discotinuation of valproate. Topiramate was tailed off. The reintroduction of valproate monotherapy caused hyperammonemia again without clinical features of encephalopathy. He also developed anticonvulsant hypersensitivity syndrome following the use of phenytoin. We propose the term topiramate-valproate-induced hyperammonemic encephalopathy syndrome to include the following features: excessive sleepiness or somnolence, aggravation of seizures, hyperammonemia, and absence of triphasic waves on electroencephalography in any individual on simultaneous topiramate-valproate therapy. The ammonia level ranged from 1.5 to 2 times normal. The serum valproate level might be within the therapeutic range. The possible mechanism is topiramate-induced aggravation of all the known complications of valproate monotherapy. This condition is reversible with cessation of either valproate or topiramate.link_to_subscribed_fulltex

Topics: Male, Hyperammonemia/*chemically induced, Fructose/administration & dosage/*adverse effects/*analogs & derivatives, Humans, Adolescent, Anticonvulsants/administration & dosage/*adverse effects, Brain Diseases/*chemically induced, Chromosome Inversion, Chromosomes, Human, Pair 15/genetics, Drug Therapy, Combination, Epilepsy/drug therapy/genetics, Valproic Acid/administration & dosage/*adverse effects, Syndrome
Publisher: 'United States Sports Academy'
Year: 2005
DOI identifier: 10.1177/08830738050200022001
OAI identifier:
Provided by: HKU Scholars Hub
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