Applicazioni farmaceutiche delle tecniche di estrusione

The extrusion is a widely applied processing technique within the plastic industry and in the last decade also in pharmaceutics. Extrusion is the process of pumping raw materials with a rotating screw through a die into a product of uniform shape. In wet extrusion the material is conditioned and softened with the addition of solvents prior to processing; in hot melt extrusion the material softens during process by applying elevated temperature. Among hot melt extrusion techniques there is injection molding. This is usually applied to realize objects with precision. Several research groups have demonstrated hot-melt extrusion processes as a viable method to prepare lots of pharmaceutical dosage forms (granules, pellets, sustained release tablets, transdermal and transmucosal drug delivery systems, implants). In this work we focused on the application of extrusion techniques for the production of a container intended for time controlled delivery of drugs. Modular release of the API should be determined either by the formulation (e.g. polymer chemo-physical characteristics) and/or thickness of the shell. Two cellulose derivatives, namely hydroxypropyl (HPC) and hydroxypropyl-methyl cellulose (HPMC) were chosen as functional polymers in virtue of their ability to slow interact with aqueous fluids. While HPC is thermoplastic and thereby able to be processed by hot melt extrusion and injection molding, HPMC is thermoplastic only at a temperatures close to degradation and so was processed in wet extrusion. The drug release performance, tested both in vitro and in vivo, was found to be dependent on the shell thickness. Moreover, injection molding technique would represent a viable way also for industrial production.