Aerodynamic particle size analysis of aerosols from pressurized metered-dose inhalers: Comparison of andersen 8-stage cascade impactor,next generation pharmaceutical impactor,and model 3321 aerodynamic particle sizer aerosol spectrometer |
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Authors: | Jolyon P Mitchell Mark W Nagel Kimberly J Wiersema Cathy C Doyle |
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Institution: | (1) Trudell Medical International, 725 Third Street, N5V 5G4 London, ON, Canada |
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Abstract: | The purpose of this research was to compare three different methods for the aerodynamic assessment of (1) chloroflurocarbon
(CFC)-fluticasone propionate (Flovent), (2) CFC-sodium cromoglycate (Intal), and (3) hydrofluoroalkane (HFA)-beclomethasone
dipropionate (Qvar) delivered by pressurized metered dose inhaler. Particle size distributions were compared determining mass
median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction <4.7 μm aerodynamic diameter
(FPF<4.7 μm). Next Generation Pharmaceutical Impactor (NGI)-size distributions for Flovent comprised finer particles than determined
by Andersen 8-stage impactor (ACI) (MMAD=2.0±0.05 μm NGI]; 2.8±0.07 μm ACI]); however FPF<4.7 μm by both impactors was in the narrow range 88% to 93%. Size distribution agreement for Intal was better (MMAD=4.3±0.19 μm
(NGI), 4.2±0.13 μm (ACI), with FPF<4.7 μm ranging from 52% to 60%. The Aerodynamic Particle Sizer (APS) undersized aerosols produced with either formulation (MMAD=1.8±0.07
μm and 3.2±0.02 μm for Flovent and Intal, respectively), but values of FPF<4.7 μm from the single-stage impactor (SSI) located at the inlet to the APS (82.9%±2.1% Flovent], 46.4%±2.4% Intal]) were fairly
close to corresponding data from the multi-stage impactors. APS-measured size distributions for Qvar (MMAD=1.0±0.03 μm; FPF<4.7 μm=96.4% ±2.5%), were in fair agreement with both NGI (MMAD=0.9±0.03 μm; FPF<4.7 μm=96.7%±0.7%), and ACI (MMAD=1.2±0.02 μm, FPF<4.7 μm=98%±0.5%), but FPF<4.7 μm from the SSI (67.1%±4.1%) was lower than expected, based on equivalent data obtained by the other techniques. Particle bounce,
incomplete evaporation of volatile constituents and the presence of surfactant particles are factors that may be responsible
for discrepancies between the techniques. |
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Keywords: | pressurized metered-dose inhaler impactor time-of-flight aerodynamic size distribution aerosol measurement |
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