Assay of paclitaxel (Taxol) in plasma and urine by high-performance liquid chromatography

A new, rapid and sensitive high-performance liquid chromatographic method for the analysis of paclitaxel (Taxol) in human plasma and urine was developed and validated. After addition of an internal standard, paclitaxel was extracted from plasma or urine by a liquid-liquid extraction using diethyl ether. Extraction efficiency averaged 90%. Chromatography was performed isocratically on a reversed-phase column monitored at 227 nm. Retention times were 7.7 and 6.7 min for paclitaxel and docetaxel, respectively, and the assay was linear in the range 25-1000 ng/ml. The limits of quantification for paclitaxel were 25 and 40 ng/ml in plasma and urine, respectively. The assay was shown to be suitable for pharmacokinetic studies of children involved in a phase I clinical trial.