Effect Of Xiao-Ai-Ping Injection On Pharmacokinetics And Tissue Distribution Of Paclitaxel In Rats

Background:Paclitaxel was isolated from the bark of Taxus brevifolius in 1968.It is a cytotoxic natural anti-tumor drug with anti-microtubule depolymerization effect,which is widely used in the treatment of various tumors.Traditional Chinese Medicine has been more and more used in combination therapy of tumor due to its effects of reducing toxicity of chemotherapy drugs,increasing sensitivity of chemotherapy agent and improving the quality of life of cancer patients.Xiao-Ai-Ping injection（XAP,it has been renamed Tong-Guan-Teng injection）is a kind of Traditional Chinese Medicine injection made of Marsdenia tenacissimae.It shows the functions of clearing away heat and detoxification,fighting cancer,etc.It is used to treat esophageal cancer,gastric cancer,lung cancer,liver cancer,ovarian cancer which can also be used as adjuvanttherapy with radiotherapy and chemotherapy.At present,XAP is often used in combination with paclitaxelin the treatment of tumors.Many published researches have reported that the combination of XAP and paclitaxel showed enhancing efficacy and reducing toxicity.However,the effect of XAP on the pharmacokinetics and tissue distribution of paclitaxel is rarely studied.Objective:In order to analyze the effect of XAP on the pharmacokinetics and tissue distribution of paclitaxel in rats,a rapid,sensitive and easy-to-use LC-MS/MS method was established for the simultaneous determination of paclitaxel and its main metabolite p-3’-hydroxypaclitaxel in rat plasma.The method was applied to the determination of paclitaxel in rats.Then,the concentration of paclitaxel and its main metabolite p-3’-hydroxypaclitaxel in the heart,liver,spleen,lung,kidney,brain,ovary and other tissues of rats were measured at the same time to explore the effect of XAP injection on the distribution of paclitaxel in the tissues of rats.Methods:A liquid chromatography-tandem mass spectroscopy assay method was developed and validated to quantify paclitaxel simultaneously and its main metabolite p-3’-hydroxypaclitaxel in rat plasma.Docetaxel was used as internal standard.The mobile phase was 0.1%formic acid water and 0.1%formic acid methanol,and the chromatographic column was Agilent ZORBAX Eclipse Plus C₁₈column（rapid resolution 4.6×50 mm,3.5μm）.Gradient elution was used with a flow rate of 0.7 m L/min and a running time of 5.5 min.Paclitaxel,p-3’-hydroxypaclitaxel and their internal standard were detected by positive ion scanning and multi-reaction monitoring mode.The specificity,recovery,matrix effect,accuracy,precision,sample stability and dilution integrity of the analytical method were verified under different storage conditions.The pharmacokinetic parameters and the concentrations of paclitaxel and its main metabolite p-3’-hydroxypaclitaxel in the tissues of rats were measured after tail intravenous administration of paclitaxel in the absence（control group）or presence of intraperitoneal administration of 10 m L/kg,20m L/kg XAP（study groups）respectively.Results:The lower limit of quantitation of paclitaxel and p-3’-hydroxypaclitaxel is 0.5ng/ml.The linear range of calibration curve is 0.5-300ng/ml.The specificity,dilution reliability,precision,accuracy and stability of the analytical method were accordance with the requirements of the guiding principles of biological sample analysis.The extraction recoveries of paclitaxel and p-3’-hydroxypaclitaxel were 96.7±3.2%,97.5±4.0%,96.1±1.8%and 94.3±7.6%,97.1±4.3%,95.3±2.4%at low,medium and high concentrations respectively.Compared with the control group,the area under the plasma concentration-time curve(AUC_0-∞)of paclitaxel increased significantly to 12572.3±2173.4μg/L*h after 10 days of continuous injection of10m L/kg XAP in the combined administration group.The clearance rate dropped to0.8±0.1 L/h/kg,and the AUC_0-∞of p-3’-hydroxypaclitaxel significantly increased to18.2±10.2μg/L*h.The AUC_0-∞of p-3’-hydroxypaclitaxel in the 20 m L/kg XAP group significantly increased to 9.9±2.1μg/L*h.The exposure of paclitaxel and its metabolite p-3’-hydroxypaclitaxel in rat liver,heart,spleen,lung and kidney tissues was increased after 10 days of pretreatment with XAP.Conclusion:A LC-MS/MS method that was simple,rapid and convenient,with good peak shape,high resolution and strong operability was established for the simultaneous determination of paclitaxel and p-3’-hydroxypaclitaxel in rat plasma.The combined administration of XAP and paclitaxel increase the exposure of paclitaxel and p-3’-hydroxypaclitaxel in rats and their distribution in liver,heart,spleen,lung and kidney tissues.The results of experiment indicated that herb-drug interaction might be existed in XAP and paclitaxel which provides scientific theoretical basis for the clinical value of the combined application of XAP and paclitaxel.