Zonisamide (ZonigrenR)
Zonisamide (ZNS) was synthesized as a benzisoxazole in 1974. It is chemically unrelated to any of the other AEDs. It is a small-ringed structure related to sulfonamide antibiotics with pH-dependent solubility in water. It had been approved by the US Food and Drug Administration (FDA) in March 2000 for the indication of partial seizures in patients older than 12 years as adjunctive therapy to other AEDs. The main mechanism of action of ZNS is reduction of neuronal repetitive firing by blocking sodium channels and preventing neurotransmitter release. It also exerts influence on T-type calcium channels and prevents influx of calcium. ZNS also exhibits neuroprotective effects through free radical scavenging.
Advantage
Good bioavailability
Indication
Partial seizure
2 GTCS
Alternative valproate for myoclonic seizure
Disadvantage
Significant drug interaction, increased by approximately 30-40%, when given concomitantly with enzyme-inducing AEDs
Sedation, fatigue, dizziness, ataxia, confusion, cognitive impairment, including word finding difficulty, weight loss/anorexia,
Depression & psychosis has also been reported, renal stone