HYDROCOLLOIDS AND GELS OF CHITOSAN AS DRUG CARRIERS

Chitosan, a natural, biocompatible polymer, is becoming popular in dos age form design. In our study the design factors affecting the release of lidocaine and lidocaine chloride from chitosan hydrocolloids and g els were studied. In hydrocolloids a relatively high viscosity was fou nd at low concentrations of chitosan caused by the increased effective volume of the polymer molecules, due to the reflection of the same ch arges in the chains. The drug release is slow and sustained, being inf luenced by the chitosan content. The mechanism of chitosan gel formati on is not known exactly, but it is clear that for gel formation the le ngth of the chitosan chains and the degree of reacetylation are respon sible. The release profile of gels follows almost zero order kinetics. Also, the degree of reacetylation is responsible for the release beha viour. The rotational motion of nitroxides (Tempol, spin-labeled lidoc aine) determined by EPR experiments showed practically equal rotationa l motion at different degrees of reacetylation. Thus, it was concluded that the free spaces, available for nitroxide rotation, were not chan ged significantly. The degree of reacetylation affects the translation al diffusion more strongly.