Preparation of silicone microspheres by emulsion polymerization: application to the encapsulation of a hydrophilic drug.

The objective of this work was to evaluate the ability of appropriate silicone elastomers to encapsulate hydrophilic compounds in microspheres prepared according to a multiphase emulsion-polymerization process. The particle size of the microspheres can be modified by controlling the usual emulsification parameters, such as the viscosity of the different phases, shear rates and surface activity properties of additives. The encapsulation efficiencies of a hydrophilic drug, propranolol hydrochloride, were very high but its release rates were very slow. Osmotic agents such as glycerol and propylene glycol did not enhance the release rate, whereas it was slightly increased by both sodium chloride addition and higher drug loading.