Pharmacologic characteristics of phenytoin include its nonlinear pharmacokinetics, variable rate of hepatic metabolism, decreased elimination rates during the first weeks of life, and variable bioavailability of the drug with various generic preparations [50,51]. In addition, a redistribution of phenytoin results in a drop in brain concentrations after the first dose. Finally, phenytoin has poor oral bioavailability in infants. Thus, phenytoin use requires individualization of dosing after initiation of therapy and should generally be avoided as a chronic maintenance medication for newborns.