Figure 1. . Aerosols can be formulated for a number of delivery modalities including metered dose inhalers and dry powder inhalers, producing solutions, suspensions or dry powders.

The outcome of the therapy can be dependent on the formulation. Aerosolization and aerosol processing are key intermediate steps that are often ignored when considering the delivery of drugs to the lungs but result in rapid changes in particle size, phase, morphology and composition, thereby affecting deposition pattern, disposition and, possibly, clinical efficacy.