Tabletting behaviour of pellets of a series of porosities - a comparison between pellets of two different compositions

The tabletting behaviour of pellets prepared from a 4:1 mixture of dicalciu m phosphate dihydrate (DCP) and microcrystalline cellulose (MCC) was studie d and compared with the tabletting behaviour of pellets made solely from mi crocrystalline cellulose (results from an earlier study by Johansson et al, ), A series of pellets with porosities in the range 26-55% were prepared an d tabletted at applied pressures of 25-200 MPa, Tablets were also formed fr om lubricated pellets. The degree of compression during compaction was calc ulated, and the porosity and tensile strength of the tablets and their perm eability to air flow were determined. The porosity of the pellets was found to significantly affect the tablettin g behaviour of the DCP/MCC pellets. However, the relationship between pelle t porosity and tablet data for the DCP/MCC pellets was different from that for the MCC pellets. The DCP/MCC pellets were generally less prone to a red uction in volume during tabletting, and the pore structure of the DCP/MCC t ablets was more closed. It was concluded that the DCP/MCC pellets were more rigid and underwent a different mode of deformation during tabletting than the MCC pellets. This mode of deformation was characterised by a more limi ted bulk deformation and a more extensive surface deformation at the pellet surfaces. The DCP/MCC pellets tended to give tablets of a lower mechanical strength. They were also less sensitive to lubrication in terms of their c ompactability, which may be explained either by less surface coverage by th e lubricant before compression or rupture of the lubricant film during comp ression caused by the more extensive surface deformation of DCP/MCC pellets . (C) 1999 Elsevier Science B.V. All rights reserved.