Intravenous administration of fosphenytoin: options for the management of seizures.

Fosphenytoin is a water-soluble disodium phosphate ester of phenytoin that is converted in plasma to phenytoin. Fosphenytoin is compatible with most common i.v. solutions and can be administered safely through the i.m.route. An additional safety factor is the absence of propylene glycol in the fosphenytoin formulation. Propylene glycol is used as a vehicle in the i.v. phenytoin preparation and by itself may produce serious cardiovascular complications. Studies of the pharmacokinetics, safety, and tolerance of i.v. fosphenytoin have demonstrated that fosphenytoin produces phenytoin plasma concentrations similar to those achieved with oral and i.v. phenytoin, but without significant cardiovascular effects and only minimal discomfort at the injection site. Aside from local reactions, the most common adverse events associated with fosphenytoin have been pruritus and reactions typical of phenytoin (e.g., dizziness, somnolence, and ataxia). Fosphenytoin represents a significant advance in the treatment of patients with seizures who require parenteral therapy.