Comparative Pharmacology
Head-to-head clinical analysis: DILANTIN versus LAMICTAL XR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DILANTIN versus LAMICTAL XR.
DILANTIN vs LAMICTAL 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.
Lamotrigine inhibits voltage-sensitive sodium channels, stabilizing neuronal membranes and inhibiting the release of excitatory neurotransmitters such as glutamate and aspartate.
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.
Lamotrigine extended-release tablets: Initial 25 mg orally once daily for 2 weeks, then 50 mg once daily for 2 weeks, then 100 mg once daily for 1 week, then 200 mg once daily; maintenance 200–400 mg once daily as adjunctive therapy for epilepsy. For bipolar disorder, dose titration as per prescribing information; typical maintenance 200 mg once daily.
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.
Terminal elimination half-life is approximately 25-33 hours in healthy adults, increasing to 50-60 hours in patients taking valproate, and decreasing to 15-27 hours in patients taking enzyme-inducing drugs like carbamazepine, phenytoin, or phenobarbital.
Primarily hepatic metabolism to inactive metabolites (p-hydroxyphenyltoin and glucuronide conjugate). Less than 5% excreted unchanged in urine. Fecal excretion minimal (<2%).
Primarily renal; ~70% of lamotrigine is excreted in urine as glucuronide conjugates, 10% as parent drug, and 20% via feces.
Category C
Category C
Anticonvulsant
Anticonvulsant