Comparative Evaluation of Glidants for Enhancing the Flowability of Poorly Flowing Powdered Materials with Varying...

Background: An increasing number of commercially available drug substances and bioactive ingredients are characterized by poor flowability. Inadequate flow properties may lead to material blockage during transport within production lines, as well as the formation of air voids within the bulk. Such phenomena can disrupt the technological process and may even result in batches that fail to meet quality requirements. Therefore, ensuring adequate powder flow is of utmost importance in the manufacture of health-related products. Methods: Binary mixtures were prepared using one of four model substances (ibuprofen, metamizole sodium, mefenamic acid, or sunflower lecithin) combined with a glidant (colloidal silica, precipitated silica, or tricalcium phosphate). The glidant content ranged from 0.5 to 10.0% w/w depending on the model substance, and mixing was carried out for 5-30 min. The resulting binary mixtures were evaluated for flow properties using the angle of repose method, and in selected cases, bulk density was also determined. Results/Conclusions: The study demonstrated that powder flow improvement depended not only on the glidant but primarily on the properties of the host material (particle size, shape, and bulk density). Coarser powders such as ibuprofen responded well to low glidant levels, although excessive silicon dioxide caused oversilication. Metamizole sodium showed progressively better flow with increasing particle size and density, and tribasic calcium phosphate further improved performance, particularly with longer mixing times. Very fine or cohesive powders, such as mefenamic acid and sunflower lecithin, showed limited response to silica-based glidants, whereas tribasic calcium phosphate proved more effective and additionally increased bulk density. Overall, no universal glidant strategy was identified; effective flow enhancement requires a tailored approach based on specific powder characteristics.