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Abstract

Powder flow is a critical attribute of pharmaceutical blends to ensure tablet weight uniformity and production of tablets with consistent and reproducible properties. This study aims at characterizing different powder blends with a number of different rheologic techniques, in order to understand how particles’ attributes and interaction between components within the formulation generate different responses when analysed by different rheological tests. Furthermore, this study intends on reducing the number of tests in early development phases, by selecting the ones that provide the best information about the flowability attributes of the pharmaceutical blends. This work considered two cohesive powders - spray-driedÌýhydroxypropyl celluloseÌý(SD HPMC) and micronizedÌýindomethacinÌý(IND) – formulated with other four commonly used excipients [(lactose monohydrated (LAC),Ìýmicrocrystalline celluloseÌý(MCC),Ìýmagnesium stearateÌý(MgSt) andÌýcolloidalsilicaÌý(CS)]. The experimental results showed that powder flowability may be affected by materials particles’ size, bulk density, morphology, and interactions withÌýlubricant. In detail, parameters, such as angle of repose (AoR), compressibility percentage (CPS), and flow function coefficient (ff_c) have shown to be highly affected by the particle size of the materials present in the blends. On the other hand, the Specific Energy (SE) and the effective angle of internal friction (φe) showed to be more related with particle morphology and materials interaction with theÌýlubricant. Since both ff_cÌýand φe parameters are generated from theÌýyield locusÌýtest, data suggest that a number of different powder flow features may be understood only by applying this test, avoiding redundant powder flow characterization, as well as extensive time and material spent in early development formulation stages.

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