A model for osmotic pressure driven release from cylindrical rubbery polymer matrices

Osmotic pressure-driven drug release from rubbery polymer matrices in a cylindrical geometry has been shown to produce a period of nearly constant release. In order to explain this behavior and in an effort to produce a tool for device design, a mathematical model of the release was developed. The model was tested by application to literature data of the release of NaI from poly(dimethylsiloxane) cylinders and found to provide good agreement with the data. The model demonstrates that, although there is a decrease in solute concentration as one moves from the exterior to the center of the cylinder, a period of nearly constant release is produced, lasting until about 60% of the initial drug load has been released. (C) 2003 Published by Elsevier B.V.