Comparison of high-performance liquid chromatographic and microbiological methods for determination of voriconazole levels in plasma

A new selective high-performance liquid chromatography (HPLC) method with U V detection for the determination of the investigational triazole voriconaz ole in human plasma by using acetonitrile precipitation followed by reverse -phase HPLC on a C-18 column was compared with a simple agar well diffusion bioassay method with Candida kefyr ATCC 46764 as the assay organism. Poole d plasma was used to prepare standard and control samples for both methods. The results of analyses with spiked serum samples (run as unknowns) were c oncordant by the bioassay and HPLC methods, with expected values being obta ined. HPLC demonstrated an improved precision (3.47 versus 12.12%) and accu racy (0.81 versus 1.28%) compared to those of the bioassay method. The rang e of linearity obtained by both methods (from 0.2 to 10 mu g/ml for HPLC an d from 0.25 to 20 mu g/ml for the bioassay) includes the range of concentra tions of voriconazole (from 1.2 to 4.7 mu g/ml) which are considered clinic ally relevant. Although either methodology could be used for the monitoring of patient therapy, the smaller variability observed with HPLC compared to that observed with the bioassay favors the use of HPLC for pharmacokinetic studies.