Development of an ultra fast liquid chromatography-tandem mass spectrometry method for simultaneous determination of cefazedone and etimicin in beagle dog plasma: Application to the pharmacokinetic study of the combination of cefazedone and etimicin injec

A new, sensitive and efficient ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method has been developed and validated for simultaneous quantification of cefazedone and etimicin in beagle dog plasma. After addition of the internal standard (IS) metronidazole, plasma samples were treated by protein precipitation procedure, and then separated on a Venusil MP C18 column (100 mm × 2.1 mm, 3.0 μm) (Venusil, China) using gradient elution with the mobile phase consisting of 0.01% heptafluorobutyric acid (HFBA) in acetonitrile and 0.01% HFBA in water at a flow rate of 0.4 mL min−1. The detection of the analytes was performed on 4000Q UFLC-MS/MS system with turbo ion spray source in the positive ion and multiple reaction-monitoring (MRM) mode. The linear range was 1.0-200 μg mL−1 for cefazedone and 0.5-100 μg mL−1 for etimicin, with lower limits of quantification of 1.0 and 0.5 μg mL−1, respectively. Intra-day and inter-day precisions were within 7.2% and 4.3%, respectively for both analytes, and the accuracy (relative error, RE, %) was less than 10.7% and 12.7%, respectively. The mean absolute extraction recoveries of analytes and IS from beagle dog plasma were all more than 73.22%. The validated method was successfully applied to the pharmacokinetic study of cefazedone and etimicin in beagle dog after intravenous administration of cefazedone injection combined with etimicin injection and the two single injections alone, respectively. The results indicated there were not obvious differences between the pharmacokinetic behaviors between the combined group and either of the single groups.