Sistemi matriciali per il rilascio prolungato di farmaci

“Prolonged release matrix systems” In the field of extended release dosage forms, hydrophilic matrices represent a subject of constant development with special relevance to the mechanism which rules over drug release kinetics. When such systems come into contact with water they swell as a consequence of polymeric chains relaxation and solvent diffusion; when water concentration exceeds a certain value the polymer undergoes a phase transition from a glassy to a rubbery state. This transition takes place at the swelling front. The primary aim of this work was to develop a simple and reliable model in which, by applying an impermeable film to the surface of the tablet and leaving only one base uncovered, the area of the swelling front can be considered almost constant during the entire release process. Moreover, this area can be easily determined. Therefore, many parameters directly related to the drug itself (solubility, particle size, formulation content) were investigated in order to evaluate their influence on the release rate using the area held by the active principle at the swelling front as a tool for analyzing drug release. A different process for matrix preparation was investigated, hot-melt extrusion, and compared with the most commonly used direct compression method. The results obtained with this strategy can open new and interesting topics requiring further investigation.