Phenytoin

Management of generalized tonic-clonic (grand mal) and complex partial seizures

Prophylaxis against seizures after trauma or surgical intervention

Treatment of ventricular arrhythmias, especially those associated with digitalis or tricyclic antidepressant toxicity

Treatment of prolonged QT interval

Treatment of epidermolysis bullosa and chronic pain syndromes

Drug of choice for status epilepticus

Treatment for acute and chronic seizures

Onset of action: 30–60 min

Protein binding >90% in adults

Elimination half-life: 22 h

95% hydroxylated and conjugated in liver with glucuronic acid for renal excretion

Therapeutic range: 10–20 μg/mL

Hydantoin derivative

In the CNS, helps to limit nerve impulse generation, thereby limiting spread of seizure focus by:

• Decreasing influx of Na ⁺ ions across cell membranes in the motor cortex

• Decreasing presynaptic Ca ²⁺ release

• Decreasing extracellular K ⁺ concentration

In the heart, works to limit reentrant arrhythmias by:

• Prolonging the effective refractory period and suppressing ventricular pacemaker automaticity

• Shortening the action potential for status epilepticus (IV and PO dosages are the same)

Pediatric: Loading dose, 15–20 mg/kg in single or divided doses, then 5 mg/kg per d in divided doses

Adult: Loading dose, 10–15 mg/kg, then 5–6 mg/kg per d in 3 divided doses

For treatment of cardiac arrhythmias: 1.5 mg/kg IV every 5 min for maximum dose of 15 mg/kg or 1.5 g