Zonisamide, a sulfonamide, is approved as adjunctive treatment for partial seizures in adults.
Zonisamide is absorbed relatively rapidly, with peak concentrations occurring in 2 to 6 hours. Zonisamide is widely distributed and is extensively bound to erythrocytes.The drug is metabolized by the CYP3A4 enzyme in the liver and is excreted in urine, primarily as the parent drug and the glucuronide metabolite.
Zonisamide’s precise mechanism of action is unknown, but it’s believed to involve stabilization of neuronal membranes and suppression of neuronal hypersensitivity.
Zonisamide is approved only as adjunctive therapy for partial seizures in adults, but it appears to have a broad spectrum of activity for other types of seizures (infantile spasms; myoclonic, gen-eralized, and atypical absence seizures).
Drugs that induce liver enzymes, such as phenytoin, carba-mazepine, and phenobarbital, increase the metabolism and de-crease the half-life of zonisamide.
Concurrent use of zonisamide with drugs that inhibit or induce CYP3A4 may increase or decrease the serum concentration of zonisamide. Zonisamide isn’t an inducer of CYP3A4, so it’s unlike-ly to affect other drugs metabolized by this system. (See Adversereactions to sulfonamides.