Liquid chromatographic determination of ketoconazole, a potent inhibitor of CYP3A4-mediated metabolism

A high-performance liquid chromatographic assay with UV detection has been developed for the determination of ketoconazole in human plasma. Quantitati ve extraction was achieved by a single solvent extraction involving a mixtu re of acetonitrile-n-butyl chloride (1:4, v/v). Ketoconazole and the intern al standard (clotrimazole) were separated on a column packed with Inertsil ODS-80A material and a mobile phase composed of wa( er-acetonitrile-tetrahy drofuran-ammonium hydroxide-triethylamine (45:50.2:2.5:0.1:0.1, v/v). The c olumn effluent was monitored at a wavelength of 206 nm with a detector rang e set at 0.5. The calibration graph was linear in the range of 20-2000 ng/m l, with a lower limit of quantitation of 20.0 ng/ml. The extraction recover ies for ketoconazole and clotrimazole in human plasma were 93 +/- 9.7% and 83 +/- 10.0%, respectively. The developed method has been successfully appl ied to a clinical study to examine the pharmacokinetics of ketoconazole in a cancer patient. (C) 2001 Elsevier Science B.V. All rights reserved.