[The control of drug release of heavy-soluble, weak basic drugs in matrix tablets using the example of medazepam].

According to ideas about the diffusion layer in the process of dissolving solids the release of medazepam as a model substance for heavy-soluble, weak alkaline substances is modified by incorporation of solid acids of different solubility and dissociation rate into the matrix. The determination of the solubility and a "virtual" pH-value within the matrix tablets leads to the evaluation of the liberation. A relatively continuous release of medazepam following different pH-values in the medium was obtained by microencapsulation of the citrus acid incorporated. Using the ideas of the diffusion layer to explain the conditions within the matrix it becomes possible to control and influence the drug release from the matrix tablet.