AN IN-VITRO METHOD FOR ASSESSING THE DURATION OF MUCOADHESION

A novel in-vitro test system was designed for measuring the duration o f adhesion of discs containing various putative mucoadhesive materials to a mucosal surface on application of a constant tensile stress. Rat small intestine was used as the model mucosal surface and all experim ents were completed in pH 6.0 isotonic phosphate buffer at 37 degrees C. In all cases adhesive joint failure resulted from a cohesive failur e within the hydrating dosage form. As expected, increasing the force applied to the mucoadhesive joint resulted in shortening of the durati on of adhesion. A rank order of duration of adhesion for various mucoa dhesive materials was obtained, which differed markedly from the rank order of adhesive strength reported in the literature. The neutral pol ymer hydroxypropylmethyl cellulose, reported to have moderate mucoadhe sive properties, showed the longest duration of adhesion when subjecte d to a constant stress of 0.0846 N. Generally, the greater the reporte d rate of swelling, the shorter the duration of adhesion. It is sugges ted that a mucoadhesive dosage form capable of rapidly forming strong interactions with the mucosal surface, but only allowing limited hydra tion to form a rigid gel, would be the ideal candidate for stable long term mucoadhesion.