Biliary excretion of diflunisal conjugates in patients with T-tube drainage

The urinary and biliary excretion of diflunisal and its glucuronide and sulphate conjugates were studied in 10 patients following cholecystectomy. Total urinary excretion (0-24 h) was 36.6 +/- 16.4% of the 250 mg dose. Biliary excretion (0-24 h) was restricted to the phenolic and acyl glucuronides and accounted for 3.7 +/- 2.3% of the dose. An inverse relationship existed between urinary and biliary excretion of diflunisal and its conjugates. The data indicate that the reduced plasma clearance of diflunisal in patients with renal failure may, at least in part, be due to increased biliary excretion of diflunisal glucuronides followed by hydrolysis in the gut and reabsorption of diflunisal i.e. enterohepatic cycling.