A novel method of characterizing medicinal drug aerosols generated from pulmonary drug delivery devices

A novel method for analyzing electromechanical properties (e.g., size, electrostatic charge, polarity) of therapeutic aerosols produced by four different commercially available pressurized metered dose inhalers (pMDIs), including Albuterol™, Atrovent™, Qvar™, and Ventolin™, is presented. Respiratory drug particles aerosolized from pulmonary drug delivery devices may not only have different aerodynamic particle size distributions but also electrostatic charge distributions. The interactive effects of these two electromechanical properties on regional deposition of inhaled aerosols in the lung airway have been acknowledged by the investigators of aerosol medicine research, which requires precise quantification for analytical perspective. Experimental studies using a multi-stage electrical low pressure impactor (ELPI) reported the net charge (q(+) or q(-)) and aerodynamic diameter (d(a)) of the pMDIs. However, the ELPI has a limitation of providing the net charge of all particles deposited on its impaction stage, not for each particle in real time. To resolve this issue, this study reports the application of an electronic single-particle aerodynamic relaxation time (ESPART) analyzer, which operates on the principle of laser Doppler velocimetry to measure simultaneously d(a), q(+), and q(-) (charge magnitude and polarity) on a single particle basis and in real time. Aerosol particles from all drug delivery devices were found to not only have different size and charge distributions but they also varied in their polarities. The drug aerosols cloud emitted by Albuterol™ and Ventolin™ were determined to be electropositive, while Atrovent™ and Qvar™ were electronegative. Count and mass distributions were reproducible for all pMDIs. In conclusion, the ESPART provided more detailed charge information about the pMDI aerosol particles.