title: Valproate-induced hyperammonemic encephalopathy in the presence of topiramate.
abstract: Two adult patients with focal epilepsy who tolerated valproate (VPA) well in different combinations of anticonvulsants developed hyperammonemic encephalopathy when treated with VPA in combination with topiramate (TPM). Topiramate may contribute to the increased ammonia level by its inhibition of carbonic anhydrase and cerebral glutamine synthetase, thereby facilitating VPA/TPM hyperammonemic encephalopathy. Recovery occurred after withdrawal of VPA or TPM.
authors.affiliation: Department of Neurology, University of Marburg, Germany. hamer@mailer.uni-marburg.de
authors.forename: H M
authors.initials: HM
authors.lastname: Hamer
authors.forename: S
authors.initials: S
authors.lastname: Knake
authors.forename: U
authors.initials: U
authors.lastname: Schomburg
authors.forename: F
authors.initials: F
authors.lastname: Rosenow
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood*; D000927:Anticonvulsants / Q000009:adverse effects*; D001927:Brain Diseases / Q000139:chemically induced* / Q000503:physiopathology; D004359:Drug Therapy, Combination; D004569:Electroencephalography; D004827:Epilepsy / Q000188:drug therapy / Q000503:physiopathology; D005260:Female; D005632:Fructose / Q000009:adverse effects / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D000077236:Topiramate; D014635:Valproic Acid / Q000009:adverse effects*
chemical_list: D000927:Anticonvulsants; D000077236:Topiramate; D005632:Fructose; D014635:Valproic Acid; D000641:Ammonia