GLC determination of griseofulvin in human plasma

A specific and quantitative GLC method for the determination of griseofulvin in human plasma is described. The method involves extraction with ether, evaporation, addition of the internal standard dissolved in benzene, and GLC analysis using an electron-capture detector. The sensitivity of the method is 0.05 mug/ml of plasma. The results obtained with this specific GLC method were compared with the results obtained with the more frequently used spectroflurometric method by analyzing duplicate plasma samples obtained from 12 subjects following a single dose of griseofulvin. It was deduced that the 30% higher plasma levels obtained spectrofluormetrically were due to the coextraction and presence of the metabolite 6-demethylgriseofulvin in the assay solutions.