title: Moderate toxic effects following acute zonisamide overdose.
abstract: Zonisamide is an antiepileptic drug that acts on voltage-sensitive sodium and calcium channels, with a modulatory effect on GABA-mediated neuronal inhibition and an inhibitory effect on carbonic anhydrase. It is used mainly for the treatment of partial seizures, and is generally well tolerated at therapeutic doses. The most common reported adverse effects are somnolence, anorexia, dizziness, and headache. There are limited data on zonisamide overdose in the literature, and no case of zonisamide mono-intoxication has been published to date. We describe the first case of zonisamide mono-intoxication in a 25-year-old woman who ingested 12.6 g of this substance with suicidal intent. Despite a plasma zonisamide concentration of 182 mg/L on admission, the patient exhibited a benign clinical course with vomiting and central nervous system depression, requiring brief intubation. Somnolence persisted for 50 hours, and normal-anion-gap metabolic acidosis and polyuria for several days. Complete recovery may be expected with supportive care, even after ingestion of large zonisamide overdoses.
authors.affiliation: Swiss Toxicological Information Centre, Zurich, Switzerland.
authors.forename: Katharina E
authors.initials: KE
authors.lastname: Hofer
authors.forename: Christian
authors.initials: C
authors.lastname: Trachsel
authors.forename: Christine
authors.initials: C
authors.lastname: Rauber-Lüthy
authors.forename: Hugo
authors.initials: H
authors.lastname: Kupferschmidt
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Kullak-Ublick
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ceschi
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects* / Q000097:blood; D002493:Central Nervous System Diseases / Q000139:chemically induced; D062787:Drug Overdose / Q000188:drug therapy; D004828:Epilepsies, Partial / Q000188:drug therapy; D005260:Female; D006801:Humans; D007555:Isoxazoles / Q000009:adverse effects* / Q000097:blood; D000078305:Zonisamide
chemical_list: D000927:Anticonvulsants; D007555:Isoxazoles; D000078305:Zonisamide