Effects of organic anions and vinblastine on biliary excretion of erythromycin in rats

Since little is known about the mechanism of biliary excretion of cationic drugs, biliary excretion of erythromycin was studied in rats. Infusion of sulfobromophthalein and taurocholate significantly decreased biliary erythromycin excretion, whereas infusion of dibromosulfophthalein, cefpiramide, ursodeoxycholate-3-O-glucuronide and taurolithocholate-3-sulfate had no effect on biliary excretion of erythromycin, Vinblastine significantly inhibited biliary erythromycin excretion, Phenothiazine treatment significantly increased biliary erythromycin excretion. However, erythromycin infusion did not affect biliary vinblastine excretion. These findings indicate a multiplicity of biliary excretory pathways for organic cations; at least one additonal pathway may exist for organic cations apart from beta-glycoprotein.