Effect of the interaction of drug-beta-cyclodextrin complex with bile salts on the drug absorption from rat small intestinal lumen.

This investigation was concerned with the change of the bioavailability of a drug owing to the interaction of the drug-beta-cyclodextrin complex with bile salts in rat intestinal lumen. The absorption of sulfamethizole (SMZ) from rat intestinal lumen after administration of SMZ-beta-cyclodextrin complex was determined by a closed-loop method in the presence or absence of bile. The blood level of SMZ after administration of SMZ-beta-cyclodextrin complex was significantly decreased in comparison with that after administration of SMZ alone in bile duct-ligated rats. On the other hand, the blood level of SMZ after SMZ-beta-cyclodextrin administration in intact rats (bile duct non-ligated) or on the addition of sodium cholate was similar to the level in the case of SMZ alone. Thus, bile salts were found to act as a competing agent in the gastrointestinal tract.