Unbound phenytoin plasma concentrations in patients comedicated with sodium valproate--the predictive value of plasma albumin concentration.

Abstract

1. Phenytoin protein binding in epileptic patients on phenytoin as monotherapy has been compared with protein binding in patients treated with both phenytoin and sodium valproate. In addition the relative value of assayed total phenytoin plasma concentrations and assayed unbound phenytoin plasma concentrations and the value of predicted unbound phenytoin plasma concentrations in predicting phenytoin toxicity has been assessed. 2. The mean phenytoin unbound fraction for patients taking sodium valproate (0.122) was significantly greater than for those on monotherapy (0.082). 3. There were six episodes of clinical toxicity. In five toxic episodes the assayed unbound phenytoin plasma concentrati..