The Influence of Flow Rate on the Aerosol Deposition Profile and Electrostatic Charge of Single and Combination Metered Dose Inhalers
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The capability of the electrostatic next generation impactor (eNGI) has been investigated as a tool capable of measuring the electrostatic charge of single (Flixotide™; containing fluticasone propionate (FP)) and combination (Seretide™; FP and salmeterol xinafoate (SX)) pressurised metered dose inhalers (pMDIs) at different flow rates.
Aerosol mass distributions were investigated at 30, 60 and 90 l.min−1 and simultaneous charge measurements recorded.
Analysis of the mass distribution data indicated a flow dependent relationship, where the aerosol performance (aerodynamic diameter <5 μm) of FP significantly increased between 30 l.min−1 and 60 l.min−1 for both formulations. No significant increase in SX was observed for Seretide with increased flow rate. Analysis of the charge distribution indicated both formulations to primarily charge negatively with a concurrent increase in charge with increased flow rate. Interestingly, the charge-tomass ratio remained relatively constant between 30 l.min−1 and 60 l.min−1 and increased at 90 l.min−1, indicating that charging was majorly influenced at the highest flow rate.
This study has shown how the eNGI could be used as a simple Pharmacopeia based methodology for the evaluation of mass and charge profiles of single and combination pMDIs at a series of flow rates.
KEY WORDSelectrostatic NGI electrostatics eNGI pMDI flow rate inhalation
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