ABSTRACT
Controlled release of drugs and other bioactive agents can be achieved by incorporating solutes either in dissolved or in dispersed form in polymers. During the design stage of these formulations or during experimental verification of their release behavior it is desirable to develop and use simple yet sophisticated mathematical models to describe the release kinetics. From a mathematical modeling point of view, controlled release systems may be classified according to the controlling physical mechanism(s) of release of the incorporated solute. In diffusion controlled release systems, the transport of solute through the polymer is achieved by molecular diffusion due to concentration gradients. Chemically controlled systems include all polymeric formulations where solute diffusion is controlled by a chemical reaction such as the dissolution of the polymer matrix or cleavage of the drug from a polymer backbone.
