Comparative pharmacokinetics of cefoperazone and cephradine in untreated streptozotocin diabetic rats

Experimental diabetes mellitus was induced in adult male rats by injecting streptozotocin (STZ; 60 mg/kg iv) for the purpose of surveying changes in the pharmacokinetics of biliary excretion after the intravenous administration of 40 mg/kg of cefoperazone (CPZ) or cephradine (CED). CPZ, CED, and other organic anions share affinity for the organic anion transport system in the bile canalicular membrane. The STZ treatment had a marked influence on the distribution and elimination of both cephalosporins. The blood levels of both cephalosporins at each time point after administration differed significantly between the STZ-treated and control rats. The values of mean residence time (MRT) of CPZ and CED were significantly decreased in the STZ-treated rats. Basal bile flow rates were increased after the administration of CPZ in the control and STZ-treated rats. Biliary clearance (CLbile) of CPZ was more than 60% of the CLtot, whereas CLbile of CED was less than 20% of CLtot in both groups of rats. The mean CLbile value of CPZ in the STZ-treated rats was 1.0 ml/min higher than that of the control rats, whereas the mean CLbile value of CED was almost the same as that of the control rats. The increased CLbile of CPZ suggested that diabetes alters the biliary excretion of CPZ. The changes in MRT of CPZ in the STZ-treated and control rats are mainly caused by an increase in the biliary excretory rate and renal clearance. The changes in MRT of CED in the STZ-treated and control rats are caused by a decrease in the apparent volume of distribution and increased renal clearance.