Pentobarbital inhibits the billiary excretion of organic acids: a study with succinysulfathiazole in the rat.

The present study was undertaken to determine whether the use of pentobarbital as an anesthetic reduces the biliary excretion of acidic drugs in rats. The drug chosen for the experiment was succinylsulfathiazole, a compound excreted unmetabolized in the bile. Animals anesthetized with urethane excreted 22.1% of the dose in the bile as compared to only 8.4% for the same time period in pentobarbital anesthetized animals. The choice of anesthetic did not affec the bile flow but did influence the bile/liver concentration gradient of succinylsulfathiazole, with the pentobarbital treated rats demonstrating a significantly lower value. Despite the higher biliary excretion of succinylsulfathiazole in the urethane treated rats, the total amount in the bile plus urine was 60% of the dose in the urethane anesthetized animals as compared with 62% in the pentobarbital treated rats. These results suggest that pentobarbital reduced the hepatic transport of succiylsulfathiazole into the bile. The question whether urethane is a preferred anesthetic for biliary excretion studies warrants further investigation.