Drug release mechanism from a microcrystalline cellulose pellet system.

A common form of modified release is the encapsulation of specially formulated or coated pellets. An important first step in the development of a multiparticulate coated dosage form is to characterize the uncoated pellet. In earlier work, an uncoated pellet system developed in these laboratories and prepared from microcrystalline cellulose (MCC) was investigated and found to exhibit both the physical characteristics of an inert matrix and varying degrees of in vitro modified release. The use and characterization of MCC as a spheronization matrix material forms the basis for this formulation study. The drug release mechanism has been verified by varying selected formulation factors and evaluating the resulting pellets according to the relationship developed by T. Higuchi for granular inert matrices. In all cases, this MCC pellet system adhered to the theoretical relationships and the drug release mechanism can, therefore, be classified as an inert matrix.