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 absorption-promoting effect was observed with dihydroxycholate; 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 on their chemical structures and/or their physicochemical properties. Solubilizing activity, hemolytic activity, lipophilicity and Ca2+ 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) .times. Ca2+ ion sequestration capacity showed higher promoting effects on rectal absorption of sodium ampicillin.