Influence of physicochemical and biological parameters on drug release from microspheres adhered on vesical and intestinal mucosa

The object of our work is to develop mucoadhesive microspheres to be applied into the urinary bladder. In the present study the microspheres were prepared and the release of a model drug after their adhesion to mucosa was evaluated. The microspheres were prepared by solvent evaporation method using Eudragit RL or hydroxypropylcellulose as matrix polymers and one out of five different polymers as mucoadhesives or non-mucoadhesive references. A method for the evaluation of the drug release from microspheres adhered on guinea pig urinary bladder and small intestine mucosa was developed and the influence of the following parameters on this process was followed: mucoadhesion strength of polymeric films, swelling of polymers and the drug release from microspheres. The results showed that the detachment forces were decreasing in the following order: CMCNa > Carbopol 934P > HPC > EE.HCl=PVP/VA. Carbopol swelled to the largest volume among all polymers and the drug release from microspheres was more retarded when Eudragit RL was used as matrix polymer. When comparing the results of pipemidic acid release from microspheres adhered on intestinal mucosa with detachment forces, similar ratios among the mucoadhesive polymers can be seen. On the other hand, differences between two mucosae were observed. These differences are due to the amount of mucus on mucosa and might also be influenced by the charge of mucus. The goal of our work at this point of investigation was achieved by microspheres containing carboxymethylcellulose as mucoadhesive and Eudragit RL as matrix polymer because they provide the longest release time from microspheres adhered on vesical mucosa and sufficient high strength of mucoadhesion. (C) 1999 Elsevier Science B.V. All rights reserved.