Using Filters to Estimate Regional Lung Deposition with Pressurized Metered Dose Inhalers

Purpose To evaluate the suitability of a recently proposed apparatus that uses filters to directly fractionate the in vitro lung dose into regional deposition estimates for use with pressurized metered dose inhaler (pMDI) devices as a less resource intensive alternative to cascade impaction. Methods Using three commercially available pMDI devices (Asmanex HFA, Ventolin HFA, QVAR), regional deposition estimates were measured directly using the filter-based apparatus (FBA). Regional deposition estimates were also generated for the same inhalers by performing cascade impaction measurements and inputting the results to an in silico regional deposition model. Regional deposition for each inhaler was evaluated at an inhalation flow rate of 30 and 60 L/min. Results Total recovery of active pharmaceutical ingredient and extrathoracic deposition was independent of method used. The regional deposition estimates provided by each method were similar and captured the same trends. Conclusions The direct measurement of estimated regional deposition is possible when using the FBA. This method is far less resource intensive than existing methods and so may be useful both for comparison of generic alternatives and the development of innovative products.