Mathematical analysis of drug release from planar matrix when drug is loaded under the solubility

The release of a drug from a planar matrix when drug loading is below saturation was analyzed mathematically, and a perfect sink was deduced from the generalized solutions. The variation of drug concentration in the matrix and the effect of the volume of the extraction medium on the release were investigated. Results show that drug concentration in a matrix is strongly dependent on its location. The profiles become steep at the matrix-medium interface. The effect of the volume of the extraction phase on the release is not important when Vr is more than 50, otherwise appreciable effects will occur. Maximum release rate is of no practical interest as it occurs at the very beginning of the process.