Design Matrix Diffusion-Controlled Systems
In a matrix diffusion-controlled system, the drug is bound to a polymeric
carrier in a dispersed form. For controlled release systems using non-
biodegradable polymeric materials as carriers, the solubility of the drug in the
system is the controlling factor for the release rate. For biodegradable
polymers, the release rate is controlled both by the solubility of the drug in
the system and by the rate of degradation of the polymeric carrier.
Matrix System Types
Homogeneous Matrix Systems
In a homogeneous matrix system, the drug is dissolved or dispersed in a
homogeneous matrix, primarily a polymer. Once the matrix system is
immersed in the dissolution medium, the drug present on the surface of the
matrix will dissolve in the dissolution medium. This will result in concentration
differences and the drug will diffuse from the inner to the outer layers of the
matrix. As a result, a depletion zone will form at the boundary of the matrix
