Diphenylhydantoin Concentrations in Saliva

Abstract
As usually measured, plasma diphenylhydantoin concentration is an estimate of the drug bound to plasma protein as well as the drug free in plasma water. The latter is less easily measured but is a better index of the biological activity of diphenylhydantoin. The present study has shown that diphenylhydantoin concentrations in saliva are similar to the concentrations of diphenylhydantoin free in plasma water. This finding makes available a convenient index of the biological activity of diphenylhydantoin, even when the plasma protein binding of the drug may be abnormal, as in uremia.