Effects of anti-epileptic drugs on the L-tryptophan binding to human serum albumin.

Effects of four anti-epileptic drugs (AED; phenobarbital, phenytoin, carbamazepine and sodium valproate) on the L-tryptophan binding to human serum albumin were studied. Among these drugs examined, only sodium valproate inhibited the binding even within the concentrations of its therapeutic range, and the Klotz plotting analysis revealed that the inhibition was competitive. The results of examinations with sera from epileptic patients medicated with these AED and drug-free normal controls also suggested that the protein binding ratios of L-tryptophan were decreased in the blood plasma of some patients with the high valproate concentrations and the low albumin contents.