Treatment of refractory trigeminal neuralgia with intravenous phenytoin

The case of a patient who was successfully treated with i.v. phenytoin for an acute exacerbation of refractory trigeminal neuralgia (TN) is reported.

A 77-year-old, 87-kg Caucasian man with a 12-year history of right-sided, classical TN was admitted for an acute exacerbation of TN refractory to pharmacologic treatment with carbamazepine, baclofen, hydrocodone-acetaminophen, tramadol, hydromorphone, and gabapentin. His medical history included atrial fibrillation, peripheral vascular disease, benign prostatic hyperplasia, and chronic ataxia secondary to antibiotic therapy in the 1970s. His outpatient medications included carbamazepine, warfarin, ergocalciferol, and saw palmetto. A 15-mg/kg dose of i.v. phenytoin sodium (1300 mg on the basis of total body weight) was recommended by neurology consultants. Because of potential adverse reactions related to high serum phenytoin concentrations and rapid infusion rates (e.g., hypotension, ataxia, nausea, vomiting, apnea, nystagmus), the patient's age, the baseline presence of atrial fibrillation and ataxia, and the fact that seizures were not being treated, the clinical pharmacist recommended dividing the 1300-mg dose into two 650-mg doses separated by four hours, with each infused at 25 mg/min; this suggestion was accepted. The patient's pain score dropped from a self-rated 12/10 to 2/10 after the first infusion and to 1/10 after completion of the second infusion. The patient's blood pressure and heart rate were monitored via telemetry every five minutes during both infusions. No adverse events were noted.

Phenytoin sodium 15 mg/kg i.v. divided into two doses separated by four hours was safe and effective in treating an acute exacerbation of refractory TN.