Effect of lubrication on the compaction properties of pharmaceutical excipients as measured by die wall pressure

The effects of lubrication on the compaction properties of pharmaceutical powders were evaluated by measuring several compaction parameters, including maximum die wall pressure (MDP), residual die wall pressure (RDP), and RDP/MDP, which is a novel parameter for evaluating the compaction properties of materials. In tableting model powders lactose and mannitol, a higher RDP/MDP and a tendency toward capping were observed. The addition of a small amount of internal lubricant to either powder decreased RDP/MDP and inhibited the capping tendency. When external lubrication was applied to the powders, similar improvements in these compaction properties were observed. However, the tensile strength of the mannitol tablet prepared under external lubrication conditions was much greater than that of the tablet prepared with 0.5% internal lubricant. On the other hand, the hardness of lactose tablets was almost the same irrespective of the lubricating method. These phenomena were explained by the plastic deformation property of mannitol and by the fragmentation of lactose particles during compression.