AIM: To elucidate the effects of cefoperazone-sulbactam on the pharmacokinetics of warfarin and the mechanism behind the enhancement of warfarin's efficacy. METHODS: Thirty-two rats were randomly assigned to four groups: WN (healthy rats after the gastric-administration of 0.125 mg/kg warfarin), WCN (healthy rats after the gastric-administration of 0.125 mg/kg warfarin and 0.3 g/kg cefoperazone-sulbactam), WO (a rat model of biliary drainage after the gastric-administration of 0.125 mg/kg warfarin), WCO (a rat model of biliary drainage after the gastric-administration of 0.125 mg/kg warfarin and 0.3 g/kg cefoperazone-sulbactam). Blood samples were collected at various time points from the femoral artery to determine the plasma concentration of warfarin and from the tail vein to measure the International Normalized Ratio (INR). Warfarin levels were quantified using LC/MS/MS, and pharmacokinetic parameters were calculated using a non-compartmental model. The expression of P-glycoprotein (P-gp) in the ileal tissues of the WN and WCN groups was determined by Western blotting. RESULTS: Compared with the WN group, the WCN group demonstrated a significant increase in AUC0-t, Cmax, and Ka, and a notable decrease in CL/F, and INR values significantly increased. However, there was no significant difference in pharmacokinetic parameters and INR values between the WO group and the WCO group. Compared to the WN group, the WO group showed a significant reduction in AUC0-t, Cmax, and CL/F, with an obvious increase in t1/2. The INR of the WCN group was significantly higher than that of the WCO group after 6 hours.Western blotting results indicated a 62.1% reduction in P-gp expression in the ileum of the WCN group compared to the WN group (P<0.01). CONCLUSION: Cefoperazone-sulbactam significantly influences the pharmacokinetic parameters of warfarin and enhances its pharmacological effect by inhibiting intestinal P-gp expression. Biliary drainage significantly affects the pharmacokinetics of warfarin rats, and there is no significant drug interaction between the two after biliary drainage.