FOSPHENYTOIN IN INFANTS

In comparison with phenytoin preparations, which have a pH value of 11 , fosphenytoin, a phosphorylated prodrug of phenytoin, has a pH value of only 8.6, which decreases the risk of cardiovascular and cutaneous side effects. The near-neutral pH value of fosphenytoin allows effecti ve intravenous or intramuscular administration. A 1-mg phenytoin equiv alent (PE) of fosphenytoin is converted to 1 mg of phenytoin in adults . We describe four infants whose seizures were treated with intravenou s fosphenytoin. We had difficulty maintaining therapeutic serum phenyt oin levels of 10 to 20 mu g/mL on doses of 5 to 8 mgPE/kg/day, and man y bolus doses of 5 to 10 mgPE/kg or maintenance doses of more than 10 mgPE/kg/day were given. Despite increased doses in three out of the fo ur patients, a therapeutic serum phenytoin level was not maintained. F rom our experience, careful and individual dosing of fosphenytoin in t his age group can be considered.