Drug release from laminated polymeric films prepared from aqueous latexes

Laminated films comprised of a drug-containing reservoir layer and a drug-free, rate-controlling membrane were prepared from aqueous latexes and investigated as an alternative drug delivery system to polymeric films cast from organic solvents. The reservoir layer was prepared by casting and drying the latex [copolymer of poly(ethylacrylate-methylmethacrylate) esters - Eudragit NE 30D (NE 30D)] containing the dissolved drugs (chlorpheniramine maleate, propranolol HCl, or salicylic acid). Monolithic solutions (salicylic acid-NE 30D) or dispersions (chlorpheniramine maleate or propranolol HCl-NE 30D) were formed, depending on the solubility of the drug in the polymer matrix. Zero-order drug release was achieved by laminating a second, drug-free latex film onto the reservoir layer. The rate-controlling membrane was either attached to, or cast directly onto the reservoir. The release rate was independent of loading for the monolithic dispersions, but dependent on loading for the monolithic solution. Release rates were enhanced by the addition of a hydrophilic polymer, hydroxypropyl methylcellulose, to the rate-controlling membrane. An inverse relationship was observed between the release rate and membrane thickness. The rate-controlling membrane, cast from organic polymer solutions, had a denser structure, resulting in slower drug release when compared with latex-cast laminates.