Interactions between food components and drugs .4. Influence of pectins and bile salts on propranolol absorption

Influence of dietary fiber components on drug absorption was studied in vitro using artificial membranes and mucosa preparations from guinea pig in 2-compartment model systems (permeation model and equilibrium dialysis). Well defined pectin preparations with different structural properties were used as food components and propranolol (P) as basic model drug. The retardation of drug was increased with decreased degree of esterification (DE) of pectin. Pectins with a blockwise distribution of free carboxyl groups possessed a more intensive effect than pectins with a random arrangement. It was found that P transport across the artificial lipid membrane was significantly decreased by pectins with a blockwise (DE less than or equal to 54%) or statistical (DE = 36%) distribution of free COOH. Pectins with lower molecular weight giving low viscosities in the medium showed only a small effect on permeation of the drug. Furthermore, the influence of bile acids without and with pectins on P absorption was studied. The bile salts did only influence P transport when they were applied above the critical micellar concentration (CMC). P transport across the lipid membranes increased slightly when pectins were additionally used to the bile salts above the CMC. Transport of P across the guinea pig mucosa was less than the permeation through the artificial lipid membranes. However, the transport of P across the mucosa was significantly reduced by glycocholic acid (GC), by pectin BL-3 as well as by BL-3 and GC in the same way as found using the artificial lipid membranes.