LC-MS/MS法测定大鼠血浆内奥沙美辛的浓度

Determination of oxametacin in rat plasma by LC-MS/MS method

目的:建立LC-MS/MS法测定奥沙美辛在大鼠血浆中的浓度,并初步研究其在大鼠体内的药动学行为。方法:血浆样品以甲基叔丁基醚(含0.5%的甲酸)液液萃取,采用ZORBAX SB-C_(18)(2.1 mm×100 mm,3.5μm)色谱柱进行色谱分离,柱温40℃,以甲醇-水-甲酸(70∶30∶0.1)为流动相,流速0.3m L·min^(-1),进样量10μL,分别以m/z 371.0→338.0和m/z 356.0→311.8为奥沙美辛和内标(吲哚美辛)的质谱检测条件。大鼠灌服5、10、20 mg·kg^(-1)奥沙美辛后,不同时间点取样测定其血浆中奥沙美辛的浓度,由DAS2.0计算药动学参数。结果:奥沙美辛质量浓度在2.0~1 000 ng·m L^(-1)内线性关系良好(r=0.999 1,权重1/X^2);定量下限为2.0 ng·m L^(-1);奥沙美辛和内标的提取回收率均高于80%,日内、日间的RSD均小于15%;奥沙美辛血浆样品在室温放置4 h,-20℃冰箱放置1月以及预处理后室温放置12 h的变化率均小于15%。奥沙美辛在大鼠体内吸收较快,达峰时间约1 h,但是吸收很差,绝对生物利用度只有约2.3%。结论:建立的方法适合于奥沙美辛的药动学研究。

Objective：To develop a rapid and accurate LC-MS/MS method for the determination of oxametacin in rat plasma and to study its pharmacokinetics in rats.Methods：Plasma samples were prepared with liquid-liquid extraction using tert-butyl methyl ether（containing 0.5%formic acid）.The separation was performed using a ZORBAX SB-C_（18） column（2.1 mm×100 mm,3.5μm）,with the column temperature of 40℃.The mobile phase was methanol-water-formic acid（70∶30∶0.1）at the flow rate of 0.3 m L·min^（-1）.The injection volume was 10μL.Tandem mass spectrometry data m/z 371.0→338.0 and m/z 356.0→311.8 were used for assaying of oxametacin and internal standard（indomethacin）.Rats were given oxametacin at a dose of 5,10 and 20 mg·kg^（-1）by oral gavage and the concentration of oxametacin in plasma was detected at the different time point.The pharmacokinetic parameters were calculated by DAS 2.0.Results：The concentration of oxametacin was linear within the range of 2.0-1 000 ng·m L^（-1）（r=0.999 1,weights 1/X^2）.The lower limit of quantitation was 2.0 ng·m L^（-1）.The extract recoveries of oxametacin and internal standard were higher than 80%.The RSDs for intra-day and inter-day detection were less than 15%.The variation of oxametacin in plasma sample was less than 15%if it was kept at room temperature for 4 hours,-20℃for one month or room temperature for 12 hours after pretreatment.The absorption rate of oxametacin in rats was rapid with Tmax of about 1 h,but the absorption was very poor.The absolute bioavailability was only about 2.3%.Conclusion：The LC-MS/MS method was established for the study of the pharmacokinetics of oxametacin.