In vitro assessment of the mucoadhesion of cholestyramine to porcine and human gastric mucosa.

Previous in vivo studies have suggested that the extended gastric residence and uniform intragastric distribution of cholestyramine may be due to mucoadherent properties. This series of in vitro investigations explored the possibility of the anion exchange resin exhibiting bioadhesive behaviour, and investigated the characteristics, such as particle size and surface charge, that may affect it. Tensile strength measurements were carried out to determine the mucoadhesion of cholestyramine and other test materials (resin particulates, polymers and hydrogels) with varying adhesive properties, to isolated porcine and human gastric mucosa. Optimal instrumental parameters for the system were determined initially and used; all procedures were carried out at room temperature (22 degrees C). The particle size of cholestyramine did not affect mucoadhesion to either porcine or human gastric mucosa (P=0.673, porcine; P=0.969, human), whilst anionic exchangers were found to provide better mucoadhesion than cationic exchangers (P=0.0002, porcine; P=0.0009, human). In some instances, it was found that the detachment forces recorded were lower with human gastric mucosa than with porcine gastric mucosa, although this was not consistently statistically significant. A rank order of mucoadhesion was constructed from a comparison of cholestyramine with eight other test materials. Cholestyramine produced the second highest degree of mucoadhesion, with Carbopol producing the greatest adhesion. Dextran and polyethylene glycol did not display good mucoadhesion under these conditions. From the findings presented here, we have found that cholestyramine demonstrates good mucoadhesion to both porcine and human gastric mucosa when compared to other known bioadhesives. It is suggested that particle size does not contribute to this mucoadherent behaviour but the surface charge of the resin has a significant part to play.