Phenytoin is one of the most useful anticonvulsant medications available for the pediatric practitioner. Although benzodiazepines are typically the first-line therapy in an emergent situation, use of phenytoin or fosphenytoin is valuable for treating most types of seizure disorders and status epilepticus, with the exception of absence seizures.

Phenytoin’s mechanism of action is by blocking voltage-sensitive sodium channels in neurons, leading to decreased neuronal electrical recovery. Its administration can cause occasional serious adverse effects, including impairment of myocardial contractility, dysrhythmias, hypotension, and cardiac arrest, as well as the less serious but concerning adverse local effects, including phlebitis, purple glove syndrome, and tissue necrosis.

The parenteral form of phenytoin is dissolved in 40% propylene glycol and 10% ethanol and adjusted to a pH of 12; sodium hydroxide is added to maintain solubility. Extravasation of the solution may cause skin irritation or phlebitis. Therefore, it is recommended that intravenous (IV) phenytoin be given via central venous access. Phenytoin administered intravenously at a rate >50 mg/min may cause hypotension and arrhythmias. These complications are believed to be secondary to the diluent, propylene glycol.