Zonisamide monotherapy for idiopathic epilepsy in dogs.

To evaluate the efficacy of zonisamide as a monotherapy in dogs with idiopathic epileptic seizure. The experiment was conducted on 10 dogs with idiopathic epilepsy that were treated at the Seoul National University Hospital for Animals. A diagnosis was conducted based on physical and neurologic examination, complete blood count and chemical analysis, magnetic resonance imaging and cerebrospinal fluid analyses. Idiopathic epilepsy was diagnosed when all of these examinations were normal. Oral zonisamide was administrated to 10 dogs with idiopathic epilepsy at 5-15 mg/kg per os every 12 h to achieve a concentration of zonisamide in serum of 10-40 μg/mL. The frequency of seizures before and after the administration of zonisamide therapy was recorded and the concentrations of zonisamide in serum were measured. Six (60%) of the dogs were favourable responders to treatment, showing a ≥50% reduction in monthly frequency of seizures. Of the remaining four, two dogs did not show a reduction and the other two showed an increase in frequency of seizures. The mean dosage of zonisamide for favourable responders was 7.92 (SD 3.79) mg/kg, which was administered orally twice a day. Only one dog, which was one of the unfavourable responders in the whole study, experienced mild side effects. Among the dogs treated with oral zonisamide, 60% responded favourably. The effect of zonisamide as an anticonvulsant drug was demonstrated in this study. Based on these results, zonisamide monotherapy is effective in some dogs with idiopathic epilepsy.