Phenytoin Sodium

What it is and how it works

Mechanism of Action The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a reduction in sustained high-frequency neuronal discharges.

Indications

Parenteral Phenytoin Sodium Injection is indicated for the treatment of generalized tonic-clonic status epilepticus, and prevention and treatment of seizures occurring during neurosurgery. Intravenous phenytoin can also be substituted, as short-term use, for oral phenytoin. Parenteral phenytoin should be used only when oral phenytoin administration is not possible . Parenteral Phenytoin Sodium Injection is indicated for the treatment of generalized tonic clonic status epilepticus and prevention and treatment of seizures occurring during neurosurgery. Intravenous phenytoin can also be substituted, as short-term use, for oral phenytoin. Parenteral phenytoin should be used only when oral phenytoin administration is not possible.

Dosage and administration (summary)

For Status Epilepticus and Non-emergent Loading Dose: Adult loading dose is 10 to 15 mg/kg at a rate not exceeding 50 mg/min. Pediatric loading dose is 15 to 20 mg/kg at a rate not exceeding 1 to 3 mg/kg/min or 50 mg/min, whichever is slower. Continuous monitoring of the electrocardiogram, blood pressure, and respiratory function is essential. Maintenance Dosing: Initial loading dose should be followed by maintenance doses of oral or intravenous Phenytoin Sodium Injection every 6 to 8 hours. ( 2.2 , 2.3 ) Intramuscular Administration: Because of erratic absorption and local toxicity, Phenytoin Sodium Injection should ordinarily not be given intramuscularly.

Contraindications

Phenytoin Sodium Injection is contraindicated in patients with: A history of hypersensitivity to phenytoin, its inactive ingredients, or other hydantoins . Sinus bradycardia, sino-atrial block, second and third degree A-V block, and Adams-Stokes syndrome because of the effect of parenteral phenytoin on ventricular automaticity. A history of prior acute hepatotoxicity attributable to phenytoin .

Warnings and precautions

Withdrawal Precipitated Seizure : May precipitate status epilepticus. Dose reductions or discontinuation should be done gradually. Serious Dermatologic Reactions : Discontinue phenytoin at the first sign of a rash, unless the rash is clearly not drug-related. If signs or symptoms suggest SJS/TEN, use of this drug should not be resumed and alternative therapy should be considered. Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan hypersensitivity : If signs or symptoms of hypersensitivity are present, evaluate the patient immediately.

Pregnancy

Pregnancy P regnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as Phenytoin Sodium Injection, during pregnancy.

Storage and supply

How Supplied Phenytoin Sodium Injection, USP—50 mg/mL 2 mL (100 mg) Single Dose vials packaged in 25s (NDC 0641-0493-25) 5 mL (250 mg) Single Dose vials packaged in 10s (NDC 0641-2555-10) Storage and Handling For single-dose only. After opening, any unused product should be discarded.

Source: Phenytoin Sodium (Phenytoin Sodium) — US FDA prescribing information, 2024-04-09, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.