Effect of absorption enhancers on the absorption of FD-4 as a poorly absorbable marker macromolecule from the liver surface in rats

The purpose of this study is to improve the rate at which drugs are absorbed from the liver surface by utilizing absorption enhancers such as extracted saponin from Saponaria officinalis (saponin), sodium caprate (Na-Cap), sodium salicylate (Na-Sal), and disodium ethylenediamine-tetraacetic acid. Fluorescein isothiocyanete-dextran with molecular weights of 4400 (FD-4) as a poorly absorbable marker macromolecule was applied to the rat liver using a cylindrical diffusion cell, in the presence or absence of the absorption enhancers. After a 15-min pre-treatment with or the co-administration of saponin or Na-Cap, the absorption ratios of FD-4 and plasma area under the curve were significantly increased, compared to control values. On the other hand, the absorption of FD-4 was increased by a 30-min pre-treatment with Na-Sal. The absorption of FD-4 applied to the rat liver was promoted by absorption enhancers. This approach could have therapeutic use for poorly absorbable compounds.