Evaluation of the Malvern Spraytec® with inhalation cell for the measurement of particle size distribution from metered dose inhalers

The purpose of this study was to evaluate the Malvern Spraytec(R) with inhalation cell attachment as a means of analyzing the particle size distribution of aerosols from pressurized metered dose inhalers (pMDIs). The aerosol particle size distribution of various commercially available, placebo, and experimental pMDI formulations was determined using Spraytec(R) under various experimental conditions and the relevant data were compared with the Andersen cascade impactor data. The Spraytec(R) volume median diameter (Dv 50) values for commercial chlorofluorocarbon- and hydrofluoroalkane (HFA)-based pMDIs were respectively smaller and higher compared with their reported mass median aerodynamic diameter values. It was possible to obtain a close agreement between Spraytec(R) D-v 50 and the reported mass median aerodynamic diameter values for a solution-type pMDI formulation, Qvar 50, by equilibrating the pMDI to 55 degreesC before the measurement and using a 20-cm throat extension. Incorporation of a nonvolatile solvent propylene glycol (PG) in placebo pMDIs (15% w/w ethanol, 0.5-20.0% w/w PG in HFA 134a) showed an increase in Dv 50 with increasing concentration of PG. Furthermore, it was possible to obtain a correlation (R-2 = 0.8037) between Spraytec(R) and Andersen cascade impactor data for the experimental nimesulide-pMDI formulations containing 0.1% w/w drug, 0.25-10% w/w PG, and 15% ethanol in HFA 134a. (C) 2004 Wiley-Liss, Inc.