QbD In Dry Powder Inhaler Development : Multifaceted Powder Characterization for Product Development

Developing products comprising fine powders remains problematic and dry powder inhalers are a prime example. Why? Because fine, dry particle behavior is notoriously more complex and variable than any single phase solid, liquid or gaseous material, where powders can exhibit the behavior of solids, liquids or gases - and sometimes all three. Product development in this area consequently remains largely based on empirical control, and as such QbD implementation in its true sense is a challenge. Successful current development is largely based on control of both input materials and processes, but often without a deeper fundamental scientific basis, limiting a true design space or any predictive capacity. The behavior of powders is often dominated by the material surfaces, and measurement of basic surface properties of real (as opposed to model and ideal) materials is often beyond current practical technology - for example, surface chemistry, electrostatic charge, surface rugosity, molecular surface structure cannot be effectively measured. Furthermore the relationship of each powder with its nominated device partner, and patient user environment can substantially change performance. This session will review some examples of the highs and lows of attempts to truly understand DPI formulation development, various techniques for powder characterization and assess the opportunities and challenges in developing effective QbD strategies for this dosage forms involving dry powders