DESIGN AND EVALUATION OF LAYERED DIFFUSIONAL MATRICES FOR ZERO-ORDER SUSTAINED-RELEASE

New layered matrix systems designed for zero-order sustained release a re presented. The devices consist of a hydrophobic middle layer and pr ess-coated hydrophillic and/or hydrophobic barrier layer(s). The syste ms overcome the inherent disadvantage of non-linear release associated with diffusion-controlled matrix devices by providing additional rele asing surface with time to compensate for the decreasing release rate. The in vitro release of pseudoephedrine hydrochloride as a model comp ound from the matrices was examined. Modulation of release from a sele cted matrix containing aminophylline was evaluated in a crossover stud y using nine beagle dogs. Preliminary in vitro/in vivo correlation was also studied. The systems described in this paper can potentially be scaled up to commercial production. (C) 1998 Elsevier Science B.V.