Influence of Compression Force on Consolidation Behavior and Drug Release Property of Wax Matrix Tablets

In order to characterize the force-dependence of the consolidation behavior and drug release properties of wax matrix tablets, granules consisting of isoniazid and hydrogenated castor oil (80 : 20) were compressed at various compression force, then the compacts obtained were tested for various properties including tablet density, crushing force and dissolution rate. The packing fraction increased with increasing compression force and reached a constant level (0.973) at a force above 1273 kg/cm2. The tensile strength of the compacts increased with the increase of the packing fraction, but it continued to increase slightly even after the packing fraction held at an almost constant value. Although the matrix structure became tighter with increasing compression force, the drug release rate from the tablet noticeably increased. Theoretical analysis of this seemingly extraordinary phenomenon provides a reasonable explanation in which the void space left after compression could not work as an effective water channel during dissolution due to the poor wettability of the matrix material. Also, the force-dependence of the disorder in the internal structure of the tablets was examined on the basis of the two-direction dissolution rate analysis. As a result, it was found that the internal disorder increased with increasing compression force, and when the compression force exceeded 1273 kg/cm2, the disorder was considerably extended.