Chitosan tablets for controlled release of theophylline: Effect of polymer-drug wet or dry blending and anionic-cationic interpolymer complex

Chitosan tablets containing theophylline were prepared by directly compressing the wet or dry blended polymer-drug powders. The effects of the viscosity and swelling ability on the release rates of drugs were examined. The theophylline releasing rates of tablets prepared by polymer-drug wet blending increase with a decrease in the viscosity of the blending chitosan solution. On the other hand, the swelling ability of the polymer greatly influences the release kinetics of the tablets prepared by polymer-drug dry blending. Tablets prepared by both polymer-drug wet and dry blending were acid-nonresisted. Tablets in simulated gastric fluid disintegrated quickly, and the drugs were released within four hours. To retard the disintegrated rate of chitosan tablets in acid medium, interpolymer complex of chitosan with anionic polyelectrolyte (alginate) is needed. By this treatment, the swelling and erosion rate of the chitosan tablets could be reduced, then controlling the release rate of the theophylline can be achieved. Drug release mechanism of the various tablets were investigated by the model of Peppas; in addition, a nuclear magnetic resonance imagine microscopy is also introduced to examine the swelling or diffusion mechanism of various tablets.