Slow-release of famotidine from tablets consisting of chitosan/sulfobutyl ether β-cyclodextrin composites

An intermolecular complex formed from a 1:1 weight ratio of chitosan (CS, molecular weight 30 kDa) and sulfobutyl ether β-cyclodextrin (SBE-β-CyD, degree of substitution 7) was less soluble than either of the original components. The release of famotidine from tablets composed of a simple mixture of CS and SBE-β-CyD is slower in media at pH 1.2 than at 6.8. Macroscopic observation of tablets and a kinetic analysis of release profiles suggested that, at pH 1.2, the drug was slowly released from the less-soluble CS/SBE-β-CyD complex formed on the surface of the tablet immediately after exposure to water, accompanied by the dissolution of the interpolymer complex and, ultimately, the erosion and disintegration of the tablet. In the case of the medium at pH 6.8, the formation of a gel by CS was the cause of the slow release, especially for CS/SBE-β-CyD tablets which were significantly gelated and both the diameter and thickness of the tablet had expanded. The in vitro slow releasing characteristic of the CS/SBE-β-CyD tablet was reflected in the in vivo absorption of the drug after oral administration to rats. These results suggest that a simple mixing of CS and SBE-β-CyD is potentially useful for the controlled release of a drug.