The biliary excretion of cefazolin.

The biliary excretion of cefazolin was studied by perfusion of isolated rabbit livers. Under these conditions, 6.7 percent of the amount of cefazolin added to the circulating blood was excreted in bile, and concentrations of drug in bile were significantly higher than concentrations in serum. Biliary excretion of cefazolin was also studied in humans after the intravenous administration of 500 mg of the drug. In 10 normal subjects, maximal concentrations of cefazolin (17.10 plus or minus 8.5 mug/ml) in the fluid obtained by duodenal tubing were attained 1-2 hr after administration of cefazolin. Concentrations were similar in bile collected by external drainage from five cholecystectomized patients (maximal levels, 14.0 plus or minus 4.7 mug/ml) 1-2 hr after injection. Assays during cholecystectomy showed that 1 hr after injection, cefazolin levels were much higher in common duct bile (31 plus or minus 11 mug/ml) than in gallbladder bile (5 plus or minus 2 mug/ml).