• Metabolism: Primarily hepatic through cytochrome P450 isoenzyme 3A4 (CYP3A4). Undergoes acetylation and reduction, forming N-acetyl zonisamide, and the open-ring metabolite 2–sulfamoylacetyl phenol, respectively. Route of Elimination: Zonisamide is excreted primarily in urine as parent drug and as the glucuronide of a metabolite. Half Life: 63 hours
• Uses/Sources: For use as adjunctive treatment of partial seizures in adults with epilepsy.
• Health Effects: May cause a potentially dangerous rash that may develop into Stevens Johnson syndrome, an extremely rare but potentially fatal skin disease.
• Symptoms: Symptoms of overdose include diminished breathing, loss of consciousness, low blood pressure, and slow heartbeat.
• Treatment: No specific antidotes for Zonisamide overdosage are available. Following a suspected recent overdose, emesis should be induced or gastric lavage performed with the usual precautions to protect the airway. General supportive care is indicated, including frequent monitoring of vital signs and close observation. (L1712)
• Route of Exposure: Oral. 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.

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.