Rapid and simple GLC determination of valproic acid and ethosuximide in plasma of epileptic patients.

A GLC method for the determination of valproic acid and ethosuximide in plasma was developed. The procedure involved a single solvent extraction of drugs from acidified plasma samples, followed by a GLC injection of the unconcentrated organic phase. This rapid, sensitive, specific, and reproducible method has been used for 2 years for the routine determination of plasma levels of valproic acid and ethosuximide in epileptic patients who receive other antiepileptic drugs simultaneously.