Diphenylhydantoin: correlation between protein binding and albumin concentration.

The unbound fraction of diphenylhydantoin is inversely correlated with the patient's serum albumin concentration and can be accurately estimated graphically without binding analyses. The data for this relationship was obtained from a study in which we observed that the unbound fraction of diphenylhydantoin was two times higher in patients with the nephrotic syndrome. However, in these patients it was not necessary to diminish the dosage since the absolute concentration of unbond drug was unchanged due to a compensatory increase in the apparent volume of distribution and plasma clearance.