Pharmacokinetics
Following a 200 to 400 mg oral Zonisamide / Zonegran dose, peak plasma
concentrations (range: 2 to 5 mcg/mL) in normal volunteers
occur within 2 to 6 hours. In the presence of food, the time to
maximum concentration is delayed, occurring at 4 to 6 hours,
but food has no effect on the bioavailability of Zonisamide / Zonegran.
Zonisamide / Zonegran extensively binds to erythrocytes, resulting in an
eight-fold higher concentration of Zonisamide / Zonegran in red blood cells
(RBC) than in plasma. The pharmacokinetics of Zonisamide / Zonegran are
dose proportional in the range of 200 to 400 mg, but the Cmax
and AUC increase disproportionately at 800 mg, perhaps due to
saturable binding of Zonisamide / Zonegran to RBC. Once a stable dose is
reached, steady state is achieved within 14 days.
The elimination half-life of Zonisamide / Zonegran in plasma is about 63
hours. The elimination half-life of Zonisamide / Zonegran in RBC is
approximately 105 hours.