Abstract: In order to study the pattern of cefotaxime metabolism in chicken plasma, an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was successfully developed for the simultaneous determination of cefotaxime and its metabolite desacetylcefotaxime. Cefotaxime at a dose of 10 mg/kg was administered to laying hen, and chicken plasma was collected at different time points to quantitate cefotaxime and desacetylcefotaxime by UPLC-MS/MS. The results showed that the limits of detection (LOD) for cefotaxime and desacetylcefotaxime were 0.07 and 0.14 μg/L, respectively; the limits of quantification (LOQ) were 0.23 and 0.99 μg/L, respectively. The recoveries of cefotaxime and desacetylcefotaxime ranged from 86.7%–95.2% and 89.5%–112%, respectively, with relative standard deviation (RSD) less than 7.7%, which met the requirements for quantitative analysis. Cefotaxime was rapidly distributed in laying hens and reached the peak (56.34 mg/L) immediately after administration, and the rate of cefotaxime metabolism was fast, which was detected at a level lower than 3.0 μg/L after 24 hours. The main metabolite deacetylcefetaxime reached its peak (10.22 mg/L) after 45 min, and it was eliminated at a relatively slow rate was and was still as high as 54.0 μg/L at 24 h after administration.

Key words: cefotaxime (CTX), desacetylcefotaxime (DCTX), ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), plasma