Effects of humidity and glidants on the flowability of pharmaceutical excipients. An experimental energetical approach during granular compaction

Granular materials are part of the design, production and final products of different industrial sectors. Powder flowability is a major topic in manufacturing and transport as it is closely related to process feasibility. Nonetheless, the flows of granular materials are not easy to describe or quantify, even in the simple case of dry monodisperse cohesionless particles.

Flowability assessment is not a standard or normalized issue; still, no test is able predict powder flow behavior in all the different mechanical situations encountered during processing. This study aims (1) to evaluate flowability, as device-related, through the force or the energy supplied to the powder bed and (2) to study the effect of glidants and moisture content on flowability. To illustrate these aims, the flowability of two well-known pharmaceutical excipients, Avicel® PH-102 and Retalac® mixed with four different types of precipitated nano-silica (SIPERNAT® D10, D17, 50 S and 500 LS), was assessed using two granular compaction devices: Densitap® and FT4® compaction cell. Our results show that the hydrophilicity of colloidal silica affects surface coverage, ranging from 6% to over 80%.

Binary mixtures with hydrophobic additives, D10 and D17, generated smaller silica aggregates with a wider spread on the surface of host particles. For Retalac® conditioned at 20% RH, HR values changed from 1.30 (acceptable flow) to 1.17 (good flow). For Avicel® PH-102, conditioned at 60% RH, HR values changed from 1.22 (fair flow) to less than 1.10 (excellent flow).

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Materials: For this study, two well-known pharmaceutical ingredients with excellent compactibility were chosen: Avicel PH-102 and RetaLac. Avicel PH-102 is a high purity microcrystalline cellulose produced by FMC Biopolymer (United States), generally used in the pharmaceutical industry to tableting by direct compression. The RetaLac is a co-processed hypromellose/lactose-based excipient produced by MEGGLE (Germany), composed of equal parts of a K-type hypromellose polymer and α-lactose monohydrate. RetaLac excipient is specifically designed for direct compression and dry granulation of modified release formulations.

Article information: Cares, Maria & Falk, Véronique. (2021). Effects of humidity and glidants on the flowability of pharmaceutical excipients. An experimental energetical approach during granular compaction. International Journal of Pharmaceutics. 604. 10.1016/j.ijpharm.2021.120747.