Pharmacokinetics and toxicity of zonisamide in cats

With the eventual goal of making zonisamide (ZNS), a relatively new antiepileptic drug, available for the treatment of epilepsy in cats, the pharmacokinetics after a single oral administration at 10 mg/kg and the toxicity after 9-week daily administration of 20 mg/kg/day of ZNS were studied in healthy cats. Pharmacokinetic parameters obtained with a single administration of ZNS at 10 mg/day were as follows: Cmax = 13.1 μg/ml; Tmax = 4.0 h; T1/2 = 33.0 h; areas under the curves (AUCs) = 720.3 μg/ml h (values represent the medians). The study with daily administrations revealed that the toxicity of ZNS was comparatively low in cats, suggesting that it may be an available drug for cats. However, half of the cats that were administered 20 mg/kg/day daily showed adverse reactions such as anorexia, diarrhoea, vomiting, somnolence and locomotor ataxia.