DETERMINATION OF ITRACONAZOLE AND HYDROXY-ITRACONAZOLE IN SERA USING HIGH-PERFORMANCE-LIQUID CHROMATOGRAPHY AND A BIOASSAY

The concentrations of itraconazole and its active metabolite, hydroxy- itraconazole, were determined in the sera of 49 patients having receiv ed itraconazole for therapeutic or prophylactic purposes. Measurements by HPLC were compared with a biological assay using a strain of Paeci lomyces variotii as test organism and itraconazole as standard. The co ncentration of hydroxy-itraconazole in serum was on average 1.6 times higher than the concentration of itraconazole. The sum of itraconazole and hydroxy-itraconazole concentrations determined by HPLC showed a l inear relationship with the concentrations obtained by the bioassay (r = 0.94). The biological method gives approximately 20% higher values than the HPLC method indicating that hydroxy-itraconazole is biologica lly more active than itraconazole. As the values of the Paecilomyces v ariotii bioassay are in the same range as the HPLC measurements, it is concluded that both methods are suitable for the monitoring of itraco nazole medication.