THE EFFECTS OF SLUGGING AND RECOMPRESSION ON PHARMACEUTICAL EXCIPIENTS

Slugs of microcrystalline cellulose (MCC), dibasic calcium phosphate (DCP) and Starch 1500 were compressed, either on their own or in various combinations, between 12.7 mm flat faced punches on a single punch tableting machine at 10 different pressures. 10 tablets of each batch were compressed and the crushing strengths for five were determined. The remaining slugs were screened through an oscillating granulator and recompressed at the same pressure used initially. The crushing strengths of the final tablets were again determined. The mean yield pressures were evaluated for the slugs utilizing Heckel analysis. The results indicated that the hardest tablets were produced using 75% MCC:25% DCP. The mean yield pressure values showed that on addition of a further excipient to MCC there is a move away from predominantly plastic deformation. This was very noticeable with blends of MCC and DCP. The latter excipient has a high mean yield pressure value which implies that it is a brittle material which deforms by fragmentation. It would seem that fragmentation of DCP within the 75% MCC:25% DCP blend enhances bonding on compaction and so leads to increased crushing strength. However, for all slugged tablets there was a reduction in the crushing strength of the tablet after the second compression for all the materials investigated. The blends consisting of Starch 1500 showed less of a reduction in the crushing strength than the other excipient blends. These results in general would indicate that the extent of plastic deformation is less when the materials are compressed twice, compared to when they are compacted once. It was concluded that the slugging process is therefore independent of an increase in dwell time.