Comparative Pharmacology
Head-to-head clinical analysis: FOSPHENYTOIN SODIUM versus ZONISADE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: FOSPHENYTOIN SODIUM versus ZONISADE.
FOSPHENYTOIN SODIUM vs ZONISADE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Fosphenytoin is a water-soluble prodrug of phenytoin. It is converted to phenytoin, which stabilizes neuronal membranes by blocking voltage-gated sodium channels, thereby inhibiting repetitive firing of action potentials and reducing seizure propagation.
Zonisamide is a sulfonamide anticonvulsant. Its precise mechanism of action is unknown, but it is believed to inhibit voltage-sensitive sodium channels and reduce T-type calcium currents, thereby stabilizing neuronal membranes and suppressing neuronal hypersynchronization. It may also modulate GABA and glutamate neurotransmission.
Loading dose: 15-20 mg PE/kg IV at 100-150 mg PE/min; maintenance: 4-6 mg PE/kg/day IV divided every 8-12 hours.
100-200 mg orally every 8 hours; maximum 600 mg/day.
None Documented
None Documented
The terminal elimination half-life of fosphenytoin is approximately 15 minutes (range 8-30 minutes) following IV administration; however, the half-life of the active metabolite phenytoin is 20-30 hours (dose-dependent) in adults, requiring careful monitoring for accumulation.
Terminal elimination half-life: 63-69 hours in adults; allows once-daily dosing; steady-state achieved in 14-21 days
Renal excretion of inactive metabolites (primarily fosphenytoin metabolites including phenytoin metabolites) accounts for approximately 80-90% of elimination; less than 5% excreted unchanged in urine; biliary/fecal excretion minimal.
Renal: approximately 62% (35% unchanged, 27% as glucuronide conjugate); fecal: 3%; biliary: negligible
Category D/X
Category C
Anticonvulsant
Anticonvulsant