Evaluation with compression equations of compression behavior of pellets with different intragranular pore volumes

Microcrystalline cellulose (MCC), calcium phosphate (DCP)/MCC (4∶1, w/w) and lactose (Lac)/MCC (4∶1) pellets with different intragranular porosity were prepared in an extrusion-spheronizator and three volume ratios of ethanol/water were used as binder agents to prepare pellets.  The compression behaviors of these pellets with different intragranular pore volume were evaluated with the parameters of Kawakita model.  The results showed that high pore volume of pellets made up of MCC had the best compressibility and low pore volume of pellets had a poor compactibility.  However, the compressibility of different porosity of pellets made up of DCP/MCC (4∶1) or Lac/MCC (4∶1) was good, but they were not significantly different.  The reason might be the main compression mechanism of high porosity of MCC pellets was plastic deformation and that of DCP/MCC pellets or Lac/MCC pellets was not plastic deformation but fragmentation.  These results can be  observed directly by the SEM photographs.  According to these results, the conclusion could be drawn that high porosity MCC pellets and different porosity DCP/MCC pellets and Lac/MCC pellets can be used as cushion granules to maintain the original shape and release characteristics of drug pellets when pellets were tabletted.