Zonisamide is a sulfonamide derivative with anticonvulsant properties. Its primary mechanism of action involves blocking voltage-dependent sodium channels and T-type calcium channels. This suppresses neuronal depolarization and hypersynchronization, thereby stabilizing abnormal electrical activity in the brain. Zonisamide also exhibits weaker inhibition of carbonic anhydrase and may modulate GABAergic and glutamatergic neurotransmission.

Zonisamide is used in combination with other medications to treat certain types of seizures. Its primary indication is as adjunctive therapy for partial-onset (focal) seizures in adults. It is also used for generalized tonic-clonic seizures, Lennox-Gastaut syndrome, infantile spasms, and myoclonic seizures. Zonisamide is administered as an oral capsule, typically taken once or twice daily. Its long half-life allows for convenient once-daily dosing in many patients. Zonisamide offers a valuable adjunctive treatment option for patients with epilepsy who are not adequately controlled on other medications.