Zonisamide is a sulfonamide anticonvulsant used to treat partial seizures. It can be found under the brand names Zonegran and Zonisade and is administered as an oral capsule. Zonisamide is a sulfonamide anticonvulsant used as an adjunctive therapy in adults with partial-onset seizures. Zonisamide may act by blocking repetitive firing of voltage-gated sodium channels, leading to a reduction of T-type calcium channel currents. By stopping the spread of seizure discharges, zonisamide prevents the extensor component of tonic convulsion, restricts the spread of focal seizures and prevents the propagation of seizures from the cortex to subcortical structures. The mechanism of action by which zonisamide controls seizures has not been fully established. However, its antiepileptic properties may be due to its effects on sodium and calcium channels. Zonisamide blocks sodium channels and reduces voltage-dependent, transient inward currents, stabilizing neuronal membranes and suppressing neuronal hypersynchronization. It affects T-type calcium currents, but has no effect on L-type calcium currents. Zonisamide suppresses synaptically-driven electrical activity by altering the synthesis, release, and degradation of neurotransmitters, such as glutamate. The use of zonisamide may lead to potentially fatal reactions. Severe reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, and aplastic anemia have been reported in patients treated with sulfonamides such as zonisamide. Zonisamide may also lead to the development of serious hematological events, drug reaction with eosinophilia and systemic symptoms (DRESS) and multi-organ hypersensitivity, acute myopia and secondary angle closure glaucoma, as well as suicidal behaviour and ideation.

Zonisamide Pathway References