Abstract: The concentration of capecitabine and 5-fluorouracil in blood and the concentration of capecitabine in the intestinal single-pass perfusion effluent were tested by UPLC-MS/MS after single exposure of SD rats by linear accelerator.C_max,T_max,t_1/2,AUC,absorption rate constant (K_a) and apparent absorption coefficient(P_app) were then calculated. It showes that the testing method is simple and reproducible,and can simultaneously determine the prototype drug capecitabine and active metabolite 5-fluorouracil in rat plasma. Our analysis indicate that the single exposure of 10 Gy in the abdomen of linear accelerator has inhibited the absorption of capecitabine into the blood circulation in the small intestine and colon,resulting in delayed peak reaching time,decreased peak concentration and blood drug concentration,and accelerated excretion,while capecitabine metabolic rate hasn’tbeen affected.

Key words: Linear accelerator, Capecitabine, Metabolism, UPLC-MS/MS