Investigation of tableting properties of excipients and their binary mixtures with two different tableting devices

Tablet is the most common pharmaceutical dosage form due to ease of administration, chemical and physical stability, and relatively low manufacturing cost. Direct compression is the preferred method for tablet production. Direct compression formulations typically contain a considerable amount of excipients. Therefore, excipients can have a significant effect on the tableting properties of formulations. More research is needed for better comprehension of the compression behaviour of different materials. The objective of this work was to investigate tableting properties of different excipients and their binary mixtures with two different laboratory scale tableting devices; the Gamlen® D1000 Powder Compaction Analyzer and the FlexiTab®. The excipients used were microcrystalline cellulose (MCC), lactose, mannitol, starch, and dicalcium phosphate (DCP). Different compression pressures were used to survey the compression behaviour of the excipients at a wide pressure range. In addition, potential effects of compression speed, dwell time, and lubrication method were considered. The excipients and their binary mixtures were characterised based on compressibility (solid fraction vs. compression pressure) and tabletability (tensile strength vs. compression pressure). The results obtained with the devices were compared to enhance process understanding. Based on the compressibility curves, it appeared that plastic deformation was the main compression mechanism of MCC and starch and fragmentation the main compression mechanism of lactose, mannitol, and DCP. The tabletability of MCC was excellent, and also the tabletability of mannitol was good. The tabletability of DCP was intermediate, whereas lactose and starch had inferior tabletabilities. In general, the tabletabilities and compressibilities of the binary mixtures were more or less what was expected based on the results of the individual materials. The results obtained with the different speed parameters and lubrication methods were mainly in line with the perceptions of the compression mechanisms of different materials. In overall, the results obtained in the Gamlen and FlexiTab experiments were quite similar. However, tensile strengths appeared generally slightly lower in the FlexiTab experiments. Probable explanations are the higher compression speed of the FlexiTab and differences in hardness measurements. This study indicated that the FlexiTab and Gamlen devices have different benefits. The Gamlen device is clearly very suitable for investigating tableting properties during formulation development, but the FlexiTab device has the advantages of higher compression speed and automatic powder feeding mechanism. Tabletability results were slightly better with the Gamlen, but more experiments are needed for solving the reasons (e.g. compression speed and hardness measurements). More information of the compression behaviour of different materials could be obtained by analyzing punch displacement data and by using different compression equations.