Comparative Pharmacology
Head-to-head clinical analysis: DILANTIN versus TEGRETOL XR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DILANTIN versus TEGRETOL XR.
DILANTIN vs TEGRETOL-XR
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Phenytoin 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 acts by blocking voltage-dependent sodium channels, thereby inhibiting the spread of seizure activity.
Carbamazepine stabilizes inactivated state of voltage-gated sodium channels, thereby inhibiting repetitive neuronal firing and reducing synaptic transmission.
300–400 mg/day orally in 2–3 divided doses; IV loading dose 15–20 mg/kg at max 50 mg/min, then 300 mg/day IV divided 2–3 times daily.
200-400 mg orally twice daily; maximum 1200 mg/day for monotherapy, 1600 mg/day for combination therapy.
None Documented
None Documented
Average 22 hours (range 7-42 hours) in adults. Dose-dependent; increases with higher concentrations due to saturable metabolism. In neonates: 10-15 hours. In chronic use, half-life may increase.
Initial: 25-65 hours; chronic dosing: 12-17 hours due to autoinduction. Steady-state reached in 2-4 weeks.
Primarily hepatic metabolism to inactive metabolites (p-hydroxyphenyltoin and glucuronide conjugate). Less than 5% excreted unchanged in urine. Fecal excretion minimal (<2%).
Renal: ~72% as unchanged drug and metabolites (primarily glucuronides). Fecal: ~28% via bile (enterohepatic recirculation possible).
Category C
Category C
Anticonvulsant
Anticonvulsant