Bio-analysis of docetaxel and hydroxylated metabolites in human plasma by high-performance liquid chromatography and automated solid-phase extraction.

A semi-automated reversed-phase high-performance liquid chromatography (HPLC) method has been developed and validated for the quantification of the novel anticancer drug docetaxel in human plasma. The chromatographic system also separated putative hydroxylated metabolites. A limited validation was performed for the assay of the metabolites while these reference compounds were not available in large quantities. The sample pretreatment of the plasma samples involves a solid-phase extraction (SPE) on Cyano end-capped columns. 2'-Methylpaclitaxel was used as internal standard. An APEX-octyl column (150 x 4.6 mm I.D.; particle size 5 microns) was used with acetonitrile-0.02 M ammonium acetate buffer pH 5 mixture as the mobile phase. UV detection was performed at 227 nm. In patient samples hydroxylated docetaxel metabolites were detected and quantified by using the docetaxel calibration curve. The accuracies and precisions of the assay fall within +/- 15% for all quality control samples and within +/- 20% for the lower limit of quantitation, which was 10 ng/ml using 1.00 ml of sample for both the parent drug and its metabolites. The overall recovery of the sample pretreatment procedure for docetaxel was 78.0% +/- 5.8% anc 84.8% +/- 3.1% for the internal standard 2'-methylpaclitaxel. Docetaxel was found to be stable in human plasma at -30 degrees C for at least 6 months. At ambient temperature docetaxel was stable for at most 15 h in human plasma.