Abstract: To study the pharmacokinetics of cyadox and its metabolites following single oral cyadox (40 mg/kg body weight) in healthy swine. A LC-MS/MS assay was used to determine plasma cyadox and its metabolites concentrations. The plasma concentration was analyzed with the pharmacokinetics software WinNonlin 5.2. Rosenblueth method of non compartment model was used to calculate the pharmacokinetic parameters of cyadox and its metabolites. The main pharmacokinetic parameters of cyadox and its metabolites were as follows. Cyadox:t_1/2 (7.52±1.77) h, C_max(0.02±0.01) μg/mL, AUC_{(0-36 h)} (0.26±0.24) (h·μg)/mL, MRT(11.37±3.21)h. N1 (cyadox 1-monoxide):t_1/2 (3.05±1.12) h, C_max(0.35±0.18) μg/mL, AUC_{(0-36 h)} (2.13±2.31) (h·μg)/mL, MRT(11.83±3.34) h. N4(cyadox 4-monoxide:t_1/2 (2.91±1.15) h, C_max(0.60±0.32) μg/mL, AUC_{(0-36 h)} (3.78±4.28) (h·μg)/mL, MRT(11.00±2.86)h. Bisdesoxycyadox:t_1/2 (3.85±1.30) h, C_max(0.46±0.19) μg/mL, AUC_{(0-36 h)} (4.21±2.47) (h·μg)/mL, MRT(13.35±2.65)h. Quinoxaline-2-carboxylic acid(QCA):t_1/2 (5.08±0.57) h, C_max(0.25±0.11) μg/mL, AUC_{(0-36 h)} (3.05±1.46) (h·μg)/mL, MRT(15.15±1.83)h. The results showed the mainly form in plasma was metabolites, concentration and area under the curve of metabolites were higher than cyadox. Cyadox is the longest elimination half-life of each metabolites, and quinoxaline -2-carboxylic acid (QCA) mean residence time is the longest time.

Key words: swine; cyadox; LC-MS/MS; QCA