Objective: The purpose of this study was to apply the rheological measurements to assess the flow properties of powders and granules and to compare the results with the standard pharmacopeial tests. Quality by design approach was utilized to better understand the compression of the solids into minitablets.Significance: Insights are provided regarding the methodology of rheological properties of powders and granules using powder flow analyzer (PFA). The 'six sigma' approach was presented as a tool for assessment of the minitablets manufacturing process.Methods: Pharmacopeial methods and rheological tests using PFA were performed to assess the flow properties of designed powder and fractionated granule mixtures - placebo and with benzodiazepines. Compression of 2.5 and 3 mm minitablets was carried out and the compression force registered during the process and weight uniformity were statistically analyzed by calculating the capability indices.Results: The flow rate measurement and cohesion test (PFA test) resulted in the best differentiation between mixtures. Higher values of capability indices were obtained for processes in which granule mixtures with better flow properties were compressed and 3 mm minitablets were produced and the usefulness of QbD tools in assessment of minitablets compression process was confirmed.Conclusion: Performed study showed that the flow properties are the critical quality attributes determining the performance of minitablets compression. The cohesion test is the most discriminative to distinguish the analyzed mixtures. Capability indices can be used to assess the manufacturing process as a useful tool in pharmaceutical development of minitablets.
Keywords: Minitablets; compression process; flow properties; process capability; quality by design.