Comparative Pharmacology
Head-to-head clinical analysis: PHENYTOIN versus ZTALMY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENYTOIN versus ZTALMY.
PHENYTOIN vs ZTALMY
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.
Ganaxolone is a positive allosteric modulator of GABAA receptors, acting at extrasynaptic and synaptic receptors to enhance chloride ion conductance and inhibit neuronal excitability.
Oral: 300-400 mg/day in 3-4 divided doses; IV: 15-20 mg/kg loading dose, then 300 mg/day maintenance.
Initial: 5 mg orally once daily for 7 days; titrate by 5 mg/day every 7 days to a maintenance dose of 30 mg once daily. Maximum: 30 mg daily.
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 30 hours (range 20-40 hours) in adults, supporting once-daily dosing. Steady-state is achieved within 5-7 days.
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%.
Primarily hepatic metabolism via glucuronidation and oxidation; <1% excreted unchanged in urine. Fecal elimination accounts for approximately 90% of the administered dose, with <5% in urine.
Category D/X
Category C
Anticonvulsant
Anticonvulsant