Biliary excretion of acetaminophen in ureter-ligated rats.

Over one fourth (28.4%) of a 100 mg/kg intravenous dose of acetaminophen (AA) is excreted into bile of conscious rats within 8 h. The main metabolite in bile was the glucuronide (14.3%), followed by the sulfate (8.2%), the glutathione conjugate (4.7%) and unchanged AA (1.2%). In rats with bilateral ligation of the ureters, the amount of total AA excreted into bile was significantly increased to 37.8% of the dose; this enhanced excretion was a consequence of augmented amounts of glucuronide (20.3%) and sulfate (12.0%) whereas the amount of the glutathione conjugate in bile was slightly diminished (4.2%). During renal failure, increased biliary elimination of AA conjugates, mainly as the sulfate, seems to partially compensate the lack of renal excretion.