COMPRESSED BARRIER LAYERS FOR CONSTANT DRUG-RELEASE FROM SWELLABLE MATRIX TABLETS

A new multi-layer tablet device is proposed for the extended release o f drugs at a constant rate. It consists of the application, during tab letting, of compressed barrier layers on one or both surfaces of a hyd rophilic matrix containing the active ingredient. The barriers can lim it the core hydration process by maintaining the planar surfaces of th e tablet covered during dissolution. Moreover, the coatings reduce the extent of the core surface exposed to the interaction with the dissol ution medium and to drug release. As a result, the release rate is red uced and the kinetics shifted towards constant drug release. The effec ts of the coating application on the release patterns of three differe nt matrix cores containing trapidil or sodium diclofenac as model drug s were tested. The matrix cores were designed to provide different rel ease mechanisms and extents. At the same time, the morphological behav iour (swelling and/or erosion processes) of the system during dissolut ion was studied.