Using an emulsion solvent evaporation process to design multi-purpose microcapsules for sustained release of water-soluble drugs and increased loading and reduced crystal transformation during interactive powder mixing

An ion-exchange resin containing porous carrier was designed and prepared using an emulsion solvent evaporation process. Encapsulation of porous water-insoluble ion-exchange resins (sodium polystyrene sulfonate and cholestyramine) in a water insoluble matrix forming polymer (cellulose propionate) introduced desirable porosity and hardness to the carrier particles. The porosity of the carrier particles was further increased by encapsulation and subsequent washout of a water-soluble polymer (1:1 w/w PEG 400 and 3350) mixture. The density of the carrier particles was improved by encapsulation of a water insoluble inert dense powder, anhydrous dibasic calcium phosphate. The formulation for preparing the carrier particles and the preparation method were successfully optimized.; The assessment of the particulate properties of the carrier particles showed that the prepared carrier microcapsules possessed higher porosity than sugar spheres and microcrystalline cellulose granules. Indirect and direct measurement of particle friability and hardness demonstrated that the microcapsule carrier particles were resistant to handling and possessed compression properties equivalent to that of MCC granules with excellent powder flow.; Encapsulation of porous ion-exchange resins into the carrier particles increased the ability of the carrier particles to carry fine drug powders during an interactive mixing process. In addition, the elasticity and low density of the carrier particles made them less sensitive to changes in the adhesion properties of the drug particles. Using very sensitive MDSC analysis it was also shown that these porous carrier particles prevented or reduced the crystallization of metastable drugs during an interactive mixing process.; These ion-exchange resins containing microcapsules provided a reliably high loading system for either cationic (acidic) drugs, or anionic (basic) drugs when used for solvent deposit drug loading. The system also protected the drugs from decomposition at elevated temperature and therefore, the drug stability was improved. Sustained release of the drugs from the resin microcapsules was achieved by formation of ion-exchange resin-drug complex.