Occurrence of fragmentation during compression of pellets prepared from a 4 to 1 mixture of dicalcium phosphate dihydrate and microcrystalline cellulose

The occurrence of pellet fragmentation during the compression of pellets prepared mainly from a hard pharmaceutical filler material was investigated. The pellets consisted of 4 parts dicalcium phosphate dihydrate (generally considered as a hard material) to 1 part microcrystalline cellulose (used as a pellet forming material). Pellets of two porosities, 36% and 55%, were prepared. Compacts formed at 100 MPa applied pressure were fractured and the fracture surfaces were then visually examined. Lubricated pellets were also compacted in order to obtain tablets which could be easily deaggregated. Pellets retrieved from deaggregated tablets were compared with uncompacted pellets with respect to size and fracture resistance. The results showed that many pellets exposed in the tablet fracture surface were fractured, especially those with higher porosity. However, the lubricated pellets retrieved from deaggregated tablets were similar in size to the uncompacted pellets, i.e. fragmentation of these pellets was minimal. Furthermore, these retrieved pellets were more resistant to fracture than the original uncompacted pellets, indicating that the formation of cracks or flaws in the pellets during compaction was also minimal. It was thus concluded that deformation and probably densification, and not fragmentation, was the dominant compression mechanisms of this pellet formulation.