In vitro aerodynamic characterization of Dry Powders for Inhalation gives a quantification of the amount of API reaching different lung regions.

However, it disregards the assessment of the drug absorption profile, which for insoluble drugs strongly depends on the dissolution of the pharmaceutical dosage form.

Still, currently there are no standard apparatus or procedures available for dissolution testing of inhaled products.

Paddle over disk (POD) apparatus is a potential test method which can be conjugated with the Next Generation Impactor (NGI) allowing for a dissolution profile assessment of a respirable fraction of the aerosol.