GROUND AND NATIVE CRYSTALS - COMPARISON OF COMPRESSION CAPACITY AND DISSOLUTION RATE

Some authors such as Huttenrauch have suggested that the trauma to cry stals during grinding may induce defects in these crystals causing dis order in the crystal lattice. This decrease in crystallinity should im prove compression capacity and dissolution rate, independently of any particle-size considerations. We have tried to study this hypothesis, using two types of crystals: aspirin and lactose a-monohydrate. For pr ecise and significant comparison, native and ground crystals must have the same particle size. Fine native crystals were separated by sievin g from a recrystallized batch. Fine ground crystals were prepared by g rinding the separated coarser crystals. Very fine crystals adsorbed on the crystal surface were removed by pneumatic sieving (Alpine(R)). Th ese two types of crystals were then studied as regards their morpholog y, crystalline state, compression capacity, and dissolution properties . From this study, it seems that no significant compression capacity i mprovement is to be observed when native and ground crystals of the sa me particle size are compared. A slight increase in the dissolution ra te of ground aspirin crystals might be ascribed to surface defects imp roving crystal wetting. Disorder seems to occur only at the crystal su rfaces. (C) 1998 Elsevier Science B.V. All rights reserved.