The use of micronized cellulose disintegrants as insoluble swellable matrices for sustained-release tablets.

Five cellulose disintegrants--low-substituted hydroxypropylcellulose (L-HPC), microcrystalline cellulose (MCC), carboxymethylcellulose (CMC), cross-linked NaCMC (C.L.NaCMC), and CaCMC-were evaluated as directly compressed matrices for sustained-release (SR) tablets in vitro, using procainamide hydrochloride as a model drug. Coarser particles (14-19 microns) of the jet mill ground disintegrants, as well as intact disintegrants, provided rapidly disintegrating tablets with fast drug release but finer particles (2.5-3.5 microns) provided matrix-type SR tablets. The SR tablets based on non-ionic polymers (L-HPC and MCC) did not disintegrate at any pH; those based on anionic polymers (C.L.NaCMC and CaCMC) did not disintegrate at pH 1.2, but they disintegrated gradually from the exterior in water and in a pH 6.8 medium. We conclude that the particle size and concentration of the cellulose disintegrants are determinant factors in the formulation of SR matrices.