Further studies on nitrofurantoin excretion in dog hepatic bile

Summary1 . Results obtained with a dog donor‐recipient model indicate that following intravenous administration of nitrofurantoin sodium, nitrofurantoin is subjected to enterohepatic cycling. At least one‐third of the nitrofurantoin originally excreted in the donors' bile after a nitrofurantoin dose of 3 mg/kg is reabsorbed intestinally in the recipients within 3 hours. 2 . After intraduodenal administration of a nitrofurantoin suspension to dogs at doses ranging from 2 to 12 mg/kg, about 10% of the dose is recovered in bile as nitrofurantoin within 6 hours. A hydrocholeretic effect was also observed which correlated with the amount of drug administered. Both biliary drug excretion and the related hydrocholeresis appeared linearly related over the drug dose range. 3 . The hydrocholeresis observed in dogs within 3 h after intravenously administered nitrofurantoin sodium, equivalent to 3 mg/kg nitrofurantoin, was at least ten times that seen following the intravenous administration of an equimolar dose of dehydrocholic acid given as its sodium salt.