Can phenytoin be given to patients?

From the Guidelines

Phenytoin can be given to patients, but it requires careful consideration and monitoring, with a recommended intravenous loading dose of 20 mg/kg, divided in maximum doses of 400 mg every 2 h orally, or 18 mg/kg IV at a maximum rate of 50 mg/min, as stated in the study by 1. The medication is primarily used to treat epilepsy and prevent seizures, with maintenance doses typically ranging from 4-6 mg/kg/day.

• Blood level monitoring is essential, with therapeutic ranges between 10-20 mcg/mL.
• Phenytoin has a narrow therapeutic window and numerous drug interactions due to its metabolism through the cytochrome P450 system.
• Common side effects include gingival hyperplasia, nystagmus, ataxia, and skin rashes.
• Long-term use may lead to osteoporosis, vitamin D deficiency, and folate deficiency.
• Phenytoin is contraindicated in patients with certain cardiac conduction abnormalities, porphyria, and hypersensitivity to hydantoins.
• It should be used cautiously in pregnant women due to potential teratogenic effects.
• Regular monitoring of drug levels, complete blood counts, liver function, and vitamin D levels is recommended during treatment, as noted in the study by 1. In terms of administration, the choice between oral and parenteral routes is at the discretion of the emergency physician, as there is a lack of evidence to support one route over the other in terms of preventing early recurrent seizure, as stated in the study by 1.
• However, intravenous loading is faster, but it may have more serious adverse effects, including hypotension, bradyarrhythmias, cardiac arrest, and extravasation injuries.
• Oral administration is cheaper, but it takes more than 5 hours to reach therapeutic levels.
• Fosphenytoin, a prodrug of phenytoin, is also available and has a lower risk of adverse cardiac effects, as noted in the study by 1.

From the FDA Drug Label

Because of the risks of cardiac and local toxicity associated with intravenous phenytoin, oral phenytoin should be used whenever possible.

The rate of intravenous administration should not exceed 50 mg per minute in adults and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) in pediatric patients.

Phenytoin Sodium Injection should not be given intramuscularly because of the risk of necrosis, abscess formation, and erratic absorption.

Phenytoin can be given to patients, but it is recommended to use oral phenytoin whenever possible due to the risks of cardiac and local toxicity associated with intravenous administration. If intravenous administration is necessary, it should be done slowly and with caution, following the recommended rate of administration. Additionally, intramuscular administration is not recommended due to the risk of necrosis, abscess formation, and erratic absorption. 2

From the Research

Administration of Phenytoin

• Phenytoin can be given to patients for the treatment of generalized tonic-clonic seizures, partial seizures with or without generalization, and convulsive status epilepticus 3, 4, 5.
• The drug is typically administered orally or intravenously, with a loading dose of 18 mg/kg given by IV infusion for the treatment of status epilepticus 5.
• Maintenance therapy with phenytoin should start at 4 to 7 mg/kg/day and be adjusted to both clinical response and serum levels 5.

Patient Considerations

• Phenytoin is not recommended as the first choice for treating epileptic seizures, except as a co-drug for managing convulsive status epilepticus, due to its potentially adverse effects 3.
• In patients with epilepsy who also have intellectual disability, and are susceptible to balance disturbances and cognitive dysfunction, it is wise to replace phenytoin with another drug, such as carbamazepine or oxcarbazepine 3.
• The long-term use of phenytoin is not recommended for patients with loss of locomotion, marked cognitive impairment, or symptoms and signs of cerebellar disease 3.

Monitoring and Safety

• The prevention of phenytoin intoxication, with the subsequent development of phenytoin-induced encephalopathy, depends on careful observation of the patients and frequent monitoring of plasma levels of phenytoin and other concomitantly administered antiepileptic drugs 3.
• Fosphenytoin, a phenytoin prodrug, has the same pharmacological properties as phenytoin but none of the injection site and cardiac rhythm complications of intravenous infusions of phenytoin, and is better tolerated and can be delivered faster than intravenous phenytoin 6.