The absence of significant biliary excretion of antipyrine or its metabolites in humans.

Three patients with complete bile duct obstructions requiring a percutaneous biliary fistuala were given an oral dose of antipyrine. Drug elimination was assessed through plasma t1/2 studies and urine and bile excretion of both antipyrine and its metabolites. Urine metabolite patterns were in agreement with reference standards, but analysis of bile revealed no antipyrine metabolites and minimal parent compound (mean of total administered dose excreted from the bile fistulas was 4%). This finding was not predicted from previous experiments in the bile-cannulated rat and suggests caution regarding interspecies extrapolation of data concerning the hepatic disposition of certain commonly used test drugs in clinical pharmacologic studies.