Guest Column: Powder Characterization Techniques For Capsule Filling

By Tim Freeman, Freeman Technology

Capsules are widely used to provide metered doses for oral and pulmonary drug delivery. For oral administration, fill weights are typically in the range 50 to 500 mg but for dry powder inhalers, dose size is far smaller, principally within the range 0.5 to 15 mg. These smaller volumes, in combination with the fine particle size of inhaler formulations, are particularly challenging. Capsule filling success relies on characterizing powders in a way that allows for a correlation between measured properties and the powder's behavior in the dosing equipment. Research has shown that bulk, shear, and dynamic powder properties all influence capsule filling performance, so powder testers with all three methodologies are uniquely applicable.