Differences in effects on drug absorption between dihydroxy and trihydroxy bile salts.

The effect of a dihydroxy bile salt, sodium taurodeoxycholate (STDC), on drug absorption from rat small intestine was investigated in comparison with that of trihydroxy one, sodium cholate (STC). The enhancement or inhibitory effects on the absorption of various model drugs by STDC bore similar tendency to those by STC, and the magnitude was greater than the latter. The absorption of sulfaguanidine was enhanced by STDC, which solubilized the phospholipids from the mucosal barrier membrane in addition to the STC-like, or ethylenediaminetetraacetate-like action. STDC inhibited the absorption of sulfadimethoxine contrary to the insignificant effect by STC. The direct action of STDC on the mucosal membrane reduced the absorption in addition to the physicochemical action, such as micellar complex formation. Quinine absorption was inhibited in the presence of STDC, which can be explained by the micellar complex formation. Possible mechanisms of the differences in the effect of STDC and STC were discussed in relation to their micellar properties.