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Plasma protein binding of phenytoin in 100 epileptic patients

journal contribution
posted on 2023-05-18, 21:52 authored by Gregory PetersonGregory Peterson, Stuart McLeanStuart McLean, Aldous, S, von Witt, RJ, Millingen, KS
The plasma protein binding of phenytoin was investigated in 100 epileptic patients, using equilibrium dialysis at 37 degrees C. The unbound fractions of phenytoin in plasma formed a skewed distribution, with a range of 9.7 to 24.7% and a median value of 12.3%. Most (80%) patients appeared to form one group with free phenytoin fractions from 9.7 to 14.5%, while the remainder formed a group with elevated free fractions (greater than 14.5%). Total and unbound plasma concentrations of phenytoin were strongly correlated (r=0.95, P less than 0.0001). There was a weak correlation between increasing age and the unbound phenytoin fraction (r=0.28, P less than 0.01). The results indicate that measurement of the total phenytoin concentration in plasma should usually provide a reliable index of anticonvulsant effect. However, determination of the unbound phenytoin fraction would be beneficial in the management of those patients in whom this fraction may be elevated, due to interacting drugs or biochemical abnormalities.


Publication title

British Journal of Clinical Pharmacology








College Office - College of Health and Medicine


Blackwell Publishing Ltd

Place of publication

United Kingdom

Repository Status

  • Restricted

Socio-economic Objectives

Evaluation of health and support services not elsewhere classified

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