Effect of Bile Salts on the Rectal Absorption of Sodium Ampicillin in Rats

Abstract

The rectal absorption of sodium ampicillin in the presence of various bile salts, such as dehydrocholate, dihydroxycholate, trihydroxycholate, and their glycine and taurine conjugates, was investigated using the in situ rat rectal loop method. A marked but variable absorptionpromoting effect was observed with dihydroxycholate, whereas trihydroxy and triketo bile salts did not enhance the rectal absorption of sodium ampicillin. These results suggest that the promoting efficacy of bile salts for rectal absorption of sodium ampicillin depends upon their chemical structures and/or their physicochemical properties. Solubilizing activity, hemolytic activity, lipophilicity and calcium ion sequestration capacity of the bile salts were measured in vitro, and the relations between promoting efficacy and physicochemical properties were investigated. The bile salts having higher hemolytic activity, higher lipophilicity, and higher values of lipophilicity (Rm value)×calcium ion sequestration capacity showed higher promoting effects on rectal absorption of sodium ampicillin.