← Search & browse all drugs

phenytoin, combinations

N03AB52

Forms & Strengths

Phenytoin sodium combinations (various oral capsules and tablets containing phenytoin with adjunct ingredients like phenobarbital)

Adult Dosing

Epilepsy: Initial 100 mg orally 3 times daily, adjusted according to therapeutic serum concentrations (target 10-20 mcg/mL)
Status epilepticus: Not typically utilized via combination fixed-dose oral formulations

Pediatric Dosing

Epilepsy: Initial 5 mg/kg/day in 2 to 3 divided doses, with subsequent dosage adjustments based on clinical response and serum levels (usual maintenance 4-8 mg/kg/day)

Indications

Control of generalized tonic-clonic seizures
Control of complex partial seizures
Prevention and treatment of seizures occurring during or after neurosurgery

Mechanism of Action

Promotes sodium efflux from neurons, stabilizing the neuronal membrane and decreasing seizure activity by reducing post-tetanic potentiation at synapses

Contraindications

Hypersensitivity to phenytoin or hydantoins
History of prior acute hepatotoxicity attributed to phenytoin
Sinus bradycardia, sinoatrial block, second- and third-degree AV block, and Stokes-Adams syndrome (due to IV formulation risks, applicable broadly)

Adverse Reactions

Nystagmus, ataxia, slurred speech, mental confusion, dizziness
Gingival hyperplasia, nausea, vomiting, constipation
Rash, Stevens-Johnson syndrome, toxic epidermal necrolysis
Megaloblastic anemia, osteomalacia, hepatitis

Drug Interactions

CYP2C9 and CYP2C19 substrate and potent inducer of multiple CYP enzymes (CYP1A2, 2C9, 2C19, 3A4), significantly lowering concentrations of co-administered drugs like warfarin, oral contraceptives, and corticosteroids
Strongly affected by CYP inhibitors (e.g., amiodarone, fluconazole) which increase phenytoin levels and toxicity risks
CNS depressants and alcohol may enhance sedative and neurological adverse effects

Curated Content: Needs Vetting Before Put to Clinical Use