Patent ID: 7182957

Claim:
A method of delivering a drug into a neutral or basic environment within a warm-blooded animal comprising: (a) providing a drug containing polymer blend that, when exposed to aqueous conditions, swells in an acidic environment and deswells in a neutral or basic environment, said polymer blend comprising: (i) an effective amount of chitosan (ii) an effective amount of a second polymer wherein said second polymer is selected from the group consisting of polyether glycols, cellulose esters, poloxamers, polysaccharides, poly vinylpyrrolidones, polyvinyl alcohols, and mixtures or copolymers thereof, said chitosan and said second polymer are not covalently or ionically crosslinked; and (iii) a drug, wherein said polymer blend is prepared by dissolving chitosan and a second polymer in an acidic aqueous solution to form an aqueous polymer blend, dehydrating said aqueous polymer blend, and recovering said polymer blend, wherein said drug is loaded simultaneous with or after said preparation of said polymer blend, and wherein said acidic aqueous solution is comprised of water and an acidifying agent selected from the group consisting of acetic acid, citric acid, hydrochloric acid, and combinations thereof, and wherein said acidic aqueous solution has a concentration from about 0.5 M to 11 M; and (b) orally administering said drug containing polymer blend to a warm-blooded animal wherein said polymer blend hydrates and swells in an acidic environment of the body and deswells in a more neutral to basic environment of the body thereby releasing said drug into the surrounding environment where in the acidic environment of the body is stomach and the neutral or basic environment of the body intestines.