Venous irritation related to intravenous administration of phenytoin versus fosphenytoin.

Study Objective: To compare the frequency, severity, and time course of venous irritation after administration of a single intravenous dose of phenytoin with an equimolar dose of fosphenytoin, a water-soluble phenytoin prodrug.

Design: Randomized, double-blind, two-period, crossover study.

Setting: University hospital clinical research unit.

Patients: Twelve healthy volunteers within 15% of ideal body weight and with no clinically significant abnormalities on physical examination, medical history, or laboratory assessment.

Interventions: Volunteers randomly received a 30-minute infusion of phenytoin sodium 250 mg (250 mg/5 ml) or an equimolar dose of fosphenytoin 375 mg (375 mg/5 ml). Subjects returned for the crossover treatment 14-21 days later.

Measurements And Main Results: Subjects assessed venous irritation (pain, burning, itching), and investigators evaluated phlebitis (erythema, swelling, tenderness), induration, exudation, and cording. Phenytoin was associated with a significantly higher degree of pain at the infusion site in all subjects and a significant degree of phlebitis in eight subjects (p < 0.05); cording occurred in six subjects. The time course of phenytoin-induced phlebitis was bimodal. Erythema and tenderness were prominent at the end of the infusion and again at 24 hours. Cording was first noted between 24 hours and 1 week after infusion. In contrast, fosphenytoin was associated with mild pain in two subjects, one incident of phlebitis, and no erythema or cording.

Conclusions: Fosphenytoin administration resulted in significantly less venous irritation and phlebitis compared with an equimolar dose of phenytoin. The clinical use of this water-soluble phenytoin prodrug should minimize the frequency and severity of infusion-site reactions and should allow convenient, rapid, intravenous administration of drug, undiluted or admixed with intravenous solutions.