Phenytoin

Drug Class

Antiepileptic (Na⁺ Channel Blocker)

Mechanism of Action (MOA)

Stabilizes inactivated voltage-gated Na⁺ channels → ↓ repetitive neuronal firing.

Black Box Warning

IV use — cardiovascular risk with rapid infusion: do not exceed 50 mg/min (adults); too-rapid IV can cause severe hypotension and cardiac arrhythmia (also applies to fosphenytoin).

Clinical Notes

Focal/tonic-clonic seizures and status. Zero-order kinetics (narrow window); gingival hyperplasia, hirsutism, nystagmus/ataxia, SJS (HLA-B*1502).

Source

FDA label

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