Prolonged-release spherical micro-matrices of ibuprofen with Eudragit RS were prepared using a novel emulsion-solvent diffusion method. Those particles were termed "microsponges" due to their characteristic sponge-like texture and unique dissolution and compression properties, unlike conventional microcapsules or microspheres. The internal porosity of microsponges could be easily controlled by changing the concentration of the drug and the polymer in the emulsion droplet(ethanol). With lower concentration of ibuprofen in the ethanol, the resultant microsponges had a higher porosity, about 50%. The drug release rate from the microsponges was interpreted by the Higuchi model of spherical matrices, which depended only on their internal porosity of the microsponges when size distribution and drug content were the same. The tortuositles in the microsponges were found to be almost constant (3-4) irrespective of porosity, suggesting the same internal texture. Microsponge compressibility was much improved over the physical mixture of the drug and polymer owing to the plastic deformation of their sponge-like structure. The more porous microsponges produced stronger tablets.
The Pharmaceutical Society of Japan