Evaluating the Particle Distribution for Dry Powder Inhalers

Fluidization and disaggregation processes during dry powder inhaler use influence the aerodynamic particle size distribution, permeation, and dissolution of the active pharmaceutical ingredient(s).

This paper describes work to develop an effective test set-up to elucidate these effects by combining laser diffraction particle size distribution measurement (Spraytec) with automated imaging, via Unidose. Unidose is an apparatus developed by Nanopharm, an Aptar company. By capturing the whole impactor sized mass it enables the application of morphologically directed Raman spectroscopy to particles in the size range associated with respiratory drug delivery. Set-ups were tested with different throat models and with different commercially available dry powders inhalers. Particle size distribution data were successfully measured by laser diffraction using the developed test set-ups, and the results were compared with those generated by imaging.