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.

Using Filters to Estimate Regional Lung Deposition with Dry Powder Inhalers.

PURPOSE: To develop an in vitro method to rapidly evaluate regional lung doses delivered by pharmaceutical inhalers. Currently, cascade impactor measurements are used, but these are resource intensive and require significant post processing of in vitro data to arrive at regional deposition estimates. METHODS: We present a specialized filter apparatus that mimics tracheobronchial (TB) deposition of pharmaceutical aerosols emitted by commercially available dry powder inhalers (DPIs). The filter housing includes an electrostatic neutralizer to eliminate artificial electrostatic filtration effects. Regional deposition (tracheobronchial and alveolar) for four DPIs (Onbrez Breezhaler, Flovent Diskus, Pulmicort Turbuhaler, and Asmanex Twisthaler) was estimated using cascade impactor measurements and an in silico regional deposition model. These estimates were compared to direct measurements of regional deposition as provided by the TB filter mimic and an absolute filter placed downstream of the TB filter housing, representing the alveolar dose. RESULTS: The two methods were shown to provide similar estimates of extrathoracic, tracheobronchial, and alveolar deposition, as well as total recovery of active pharmaceutical ingredients. CONCLUSIONS: Because of its design, the TB filter apparatus makes it possible to estimate regional deposition with inhalers directly using variable inhalation profiles without any additional equipment or changes to the experimental configuration. This method may be useful to expedite development of both innovative and generic drug products as it provides regional respiratory tract deposition estimates using fewer resources than exisiting methods.