Comparative Pharmacology
Head-to-head clinical analysis: CEREBYX versus PHENYTOIN SODIUM.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CEREBYX versus PHENYTOIN SODIUM.
CEREBYX vs PHENYTOIN SODIUM
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Fosphenytoin is a prodrug of phenytoin, which stabilizes neuronal membranes by blocking voltage-gated sodium channels, thereby inhibiting repetitive firing of action potentials.
Stabilizes neuronal membranes and decreases seizure activity by increasing efflux or decreasing influx of sodium ions across cell membranes in the motor cortex during generation of nerve impulses. Prolongs inactivation of voltage-gated sodium channels, reducing repetitive firing of action potentials.
Loading dose: 15-20 mg PE/kg IV/IM (max 1500 mg PE); maintenance: 4-6 mg PE/kg/day IV/IM divided q12h or q8h. Switch to oral phenytoin at equivalent dose.
Loading dose: 15-20 mg/kg IV (not to exceed 50 mg/min) or oral (1000-1500 mg total in divided doses). Maintenance: 300-400 mg/day PO in 1-2 divided doses or IV (100 mg every 6-8 hours).
None Documented
None Documented
The terminal elimination half-life of fosphenytoin (converted to phenytoin) is approximately 15 hours (range 10-20 hours) in adults with normal hepatic function; after conversion, phenytoin half-life is dose-dependent and averages 22 hours (range 7-42 hours) at therapeutic concentrations.
Mean terminal half-life 22 ± 9 hours (range 7–42 hours), dose-dependent and saturable due to Michaelis-Menten kinetics; half-life increases with higher serum concentrations. Steady state achieved after 7–10 days.
Renal excretion of unchanged drug and metabolites accounts for approximately 80% of the dose; about 20% is eliminated in feces via biliary excretion.
Primarily hepatic metabolism (CYP2C9, CYP2C19); <5% excreted unchanged in urine. Metabolites (majority p-HPPA) are excreted renally as glucuronide conjugates. Fecal elimination negligible (<2%).
Category C
Category D/X
Anticonvulsant
Anticonvulsant