Development of a Reproducible Powder Characterization Method Using a Powder Rheometer

In this study, a powder rheometer was used to measure flow characteristics of two pharmaceutical model powders. Precise measurements were obtained for one of the model powders whereas the results were less precise for the second powder. In conclusion, further work is needed to increase the mechanistic understanding of powder rheological measurements. INTRODUCTION Modern pharmaceuticals are primarily manufactured by empirical approaches and batch-wise unit operations. However, regulatory authorities have started to require that future manufacturing schemes should be developed, monitored and controlled based on a mechanistic understanding of how material attributes and process parameters affect the performance of the final product. Yet, the mechanistic understanding of pharmaceutical powder processing is inadequate and generally relies on a few methods that are not very discriminative, e.g. flow through a funnel or Carr’s Compressibility Index as defined in several Pharmacopoeia tests. New tools for studying powders are therefore needed in order to increase the current understanding of underlying principles affecting powder behavior. The Freeman Technology 4 (FT4) bench-top powder rheometer, previously described elsewhere in the literature, might be such a tool due to the fact that it is designed to characterize powders under various conditions in ways that resemble large-scale production environments. In addition, the powder rheometer is able to measure several parameters related to process performance of powders. These methods include rheological, permeability, compressibility and torsional shear tests. Within the recent years, several studies have been published using a FT4 powder rheometer to investigate and characterize different powder properties. Though the FT4 rheometer does not provide direct inprocess measurements of powder properties, it is indeed a promising tool for increasing the mechanistic understanding of powder behavior in lab-scale. The knowledge obtained in the laboratory can then be transferred and applied to large-scale processes. In 2011, Dumarey et al. showed how methods provided by the FT4 powder rheometer can be of great value to understand how raw material attributes Development of a Reproducible Powder Characterization Method Using a