Characterization of the properties of powder excipients commonly used in pharmaceutical compounding

Capsules are the most popular and versatile dosage form produced in pharmaceutical compounding. In the preparations of capsules, powder excipients are nonactive ingredients that can be used for the purpose of increasing bulk, enhancing flow, and improving stability of a powder formulation. Flow properties of powder excipients can impact not only the compounding procedure, but also the uniformity and quality of the final product. In this study, an FT4 Powder Rheometer was used to compare dynamic, bulk, and shear properties of the following four powder excipients: Loxoral, Loxasperse, a commercial powder excipient, and lactose monohydrate. Changes in flow energy, measured as the powders are exposed to external conditions such as air, compression, consolidation, and shear forces, were used to compare flow properties of the four excipients. Results show Loxasperse to have superior dynamic properties, indicating more efficient packing potentials. Though Loxoral did not have the most favorable flow in terms of dynamic properties, Loxoral outranked the other excipients when comparing bulk and shear properties. Taking into account processing equipment and the external environment, compounding pharmacists can reevaluate current formulas to include excipients with more favorable flow properties, resulting in more uniform and higher quality products.