Plasma protein binding of phenytoin after cholecystectomy and neurosurgical operations.

The purpose of the present study was to investigate whether changes in the protein binding of phenytoin occur postoperatively. Fourteen patients were studied after cholecystectomy and six patients after operations for intracranial aneurysm or meningeoma. It was found that the fraction of phenytoin not bound to plasma proteins rose significantly after operation. The total concentration, on the other hand, decreased, so the concentration of free phenytoin did not change much. Possible explanations to the changes observed are discussed, as well as the clinical usefulness of determination of the protein binding of phenytoin.