ABSTRACT
The manufacturer of fosphenytoin advises that the fosphenytoin dosage, concentration in solutions, and infusion rate always be expressed in terms of phenytoin sodium equivalents. A dosage of 1.5 mg of fosphenytoin is converted after intramuscular or intravenous injection to 1 mg phenytoin. The rate of conversion of fosphenytoin to phenytoin may be increased among patients who have significant kidney or liver dysfunction and those who have hypoalbuminemia. Fosphenytoin is indicated for the short-term (1 week or less) replacement of injectable or oral phenytoin pharmacotherapy when it is unavailable or is considered to be inappropriate or of less therapeutic benefit for the patient. Fosphenytoin is an inactive prodrug that is converted in vivo to phenytoin. Fosphenytoin is completely absorbed and converted to phenytoin following intramuscular injection. Peak blood concentrations are obtained within 30 minutes following intramuscular injection. Fosphenytoin is bound to plasma proteins extensively.
