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Zonisamide
- indication:For use as adjunctive treatment of partial seizures in adults with epilepsy.
- pharmacologypharmacology:
- mechanism: Zonisamide binds to sodium channels and voltage sensitive calcium channels, which suppresses neuronal depolarization and hypersynchronization. Zonisamide also inhibits carbonic anhydrase to a weaker extent, but such an effect is not thought to contribute substantially to the drug's anticonvulsant activity.
- toxicity: Symptoms of overdose include diminished breathing, loss of consciousness, low blood pressure, and slow heartbeat.
- absorprion: Variable, yet relatively rapid rate of absorption with a time to peak concentration of 2.8-3.9 hours. Food has no effect on the bioavailability of zonisamide.
- halflife: 63 hours
- roouteelimination: Zonisamide is excreted primarily in urine as parent drug and as the glucuronide of a metabolite.
- volumedistribution: * 1.45 L/kg
- clearance: * 0.30 - 0.35 mL/min/kg [patients not receiving enzyme-inducing antiepilepsy drugs (AEDs)] * 0.35 - 0.5 mL/min/kg [Concomitant administration of phenytoin and carbamazepine]