Simple gas-chromatographic measurement of valproic acid in psychiatric patients: effect on levels of other simultaneously administered anticonvulsants.

A simple, rapid and precise gas-chromatographic procedure which involves one-step extraction and on-column methylation for routine clinical monitoring of plasma valproic acid levels is described. Six other commonly, simultaneously administered anticonvulsants can also be determined by substituting methylene chloride for chloroform for extraction and changing the column temperature. Also, described is the effect of valproic acid on blood levels of other simultaneously administered anticonvulsants.