Comparative Pharmacology
Head-to-head clinical analysis: PHENYTOIN versus QUDEXY XR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENYTOIN versus QUDEXY XR.
PHENYTOIN vs QUDEXY XR
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Phenytoin is a hydantoin anticonvulsant that 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. It use-dependently blocks voltage-gated sodium channels, prolonging their inactivation phase and reducing high-frequency repetitive firing of action potentials.
Stabilizes neuronal membranes and inhibits repetitive firing of action potentials via blockade of voltage-gated sodium channels; also enhances GABAergic activity and inhibits glutamate release.
Oral: 300-400 mg/day in 3-4 divided doses; IV: 15-20 mg/kg loading dose, then 300 mg/day maintenance.
Initial dose 25 mg orally twice daily; titrate by 25-50 mg/day every 1-2 weeks to target dose of 200-400 mg/day in two divided doses. Maximum 400 mg/day.
None Documented
None Documented
Clinical Note
moderatePhenytoin + Digoxin
"The metabolism of Digoxin can be increased when combined with Phenytoin."
Clinical Note
moderateFosphenytoin + Digoxin
"The metabolism of Digoxin can be increased when combined with Fosphenytoin."
Clinical Note
moderatePhenytoin + Digitoxin
"The metabolism of Digitoxin can be increased when combined with Phenytoin."
Clinical Note
moderateFosphenytoin + Digitoxin
"The metabolism of Digitoxin can be increased when combined with Fosphenytoin."
Average terminal half-life 22 hours (range 7–42 hours) in adults; dose-dependent due to saturation of metabolism at therapeutic concentrations (10–20 mg/L). Half-life increases with higher doses.
Terminal elimination half-life is approximately 70-90 hours after multiple dosing, supporting twice-daily dosing; requires slow titration to steady state (2-3 weeks).
Primarily hepatic metabolism (>95%); less than 5% excreted unchanged in urine. Renal excretion of metabolites (glucuronides) accounts for ~80% of elimination; biliary/fecal excretion of metabolites ~20%.
Renal: approximately 70% as unchanged drug; fecal: approximately 20%; biliary: minor (<5%).
Category D/X
Category C
Anticonvulsant
Anticonvulsant