Sustained release chitosan microspheres prepared by novel spray drying methods

Modified spray drying methods, especially a novel w/o/w emulsion-spray dryi ng method, were developed to prepare chitosan microspheres with a sustained drug release pattern. Release of the model drugs cimetidine and famotidine , from the microspheres prepared by the emulsion-spray drying methods, was greatly retarded with release lasting for several hours, compared with drug loaded microspheres prepared by conventional-spray drying or emulsion meth ods where drug release was almost instant. The slow release of drug was par tly due to the poor wetting ability of the microspheres which floated on th e surface of the dissolution medium. The addition of a wetting agent increa sed the release rate significantly. The coating of the microspheres with ge latin decreased the rate of release of drug in the presence of wetting agen ts.