he principal component of many solid pharmaceutical formulations and indeed of dry powder inhalers, rather than being an active pharmaceutical ingredient (API), is most likely to be lactose. It is an excipient that fulfils a number of functions including those of diluent, flow-aid and API carrier. 

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Pulmonary Drug Delivery: Advances and Challenges

Published Online: 29 MAY 2015

DOI: 10.1002/9781118799536.ch7