Biliary cefpiramide excretion: its relation to biliary excretion of bile acids and sulfobromophthalein

Cefpiramide, a beta-lactam antibiotic, has been reported to be excreted from hepatocytes into the bile by a carrier-mediated system. Herein, the relationship of biliary cefpiramide excretion to the excretion of bile acids and sulfobromophthalein was studied in rats. Biliary cefpiramide excretion was markedly inhibited by sulfobromophthalein, lithocholate-3-O-glucuronide and taurolithocholate-3-sulfate, whereas it was not inhibited by ursodeoxycholate or taurocholate. However, the inhibitory effect of cefpiramide on the biliary excretion of sulfobromophthalein or lithocholate-3-sulfate was very small. These findings indicate that, although cefpiramide is excreted by a process common to organic anions and bile acid sulfate and glucuronide, two or more excretory pathways for organic anions exist and cefpiramide has affinity for only one of these carriers.