Zonisamide (Synonyms: CI-912, PD 110843)

Zonisamide is a 1,2 benzisoxazole derivative and the first agent of this chemical class to be developed as an antiepileptic drug.Target: Calcium channel inhibitor; Sodium channel inhibitorZonisamide is a sulfonamide anticonvulsant approved for use as an adjunctive therapy in adults with partial-onset seizures for adults; infantile spasm, mixed seizure types of Lennox-Gastaut syndrome, myoclonic, and generalized tonic clonic seizure. Zonisamide is a 1,2 benzisoxazole derivative and the first agent of this chemical class to be developed as an antiepileptic drug. It has shown activity in various animal models of epilepsy, and although a detailed mode of action awaits clarification it appears to block the propagation/spread of seizure discharges and to suppress the epileptogenic focus [1].Zonisamide 500 mg/day was significantly superior to placebo in reducing the frequency of complex partial seizures (-51% versus -16%), all partial seizures and all seizures, with dose-dependent benefit provided over a 100-500 mg/day dose range. Supporting trials have confirmed significant increases in reduction in median seizure frequency (up to 41%) and responder rates (35-42%) compared with placebo following zonisamide 400-600 mg/day, enabling 20-27% of patients to attain >or=75% reduction in seizure frequency [2].Clinical indications: Epilepsy; Lewy body dementia; Parkinsons diseaseToxicity: Anorexia; Somnolence; Dizziness; Irritability; Confusional state; Depression; Diplopia; Memory impairment

References:
[1]. Peters DH, et al. Zonisamide. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in epilepsy. Drugs. 1993 May;45(5):760-87.
[2]. Brodie MJ, et al. Zonisamide as adjunctive therapy for refractory partial seizures. Epilepsy Res. 2006 Feb;68 Suppl 2:S11-6. Epub 2005 Nov 28.