AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Quantifying Pharmaceutical Aerosol Dissolution at Relative Humidities >99.5%
ALLEN E. HADDRELL, Grazia Rovelli, David Lewis, Tanya Church, Jonathan P. Reid, University of Bristol
Abstract Number: 97 Working Group: Health-Related Aerosols
Abstract The efficacy of an inhaled pharmaceutical aerosol is dependent on the size and structure of the aerosol particles at the point of inhalation, its composition, and the microphysical processes that occur during inhalation. The degree to which/if particles grow when inhaled directly affects both where the dose is delivered and particle/droplet structure upon deposition. An understanding of this dynamic behaviour is critical to predicting regional and total dose, drug uptake, and pharmacokinetic rates. To be presented here is a comprehensive approach to probe all of these dynamic processes simultaneously for individual droplets produced from MDI, DPI and nebulizer starting formulations.
To study these effects, a new electrodynamic trap is to be reported. Novel features of the this trap include: (1) can capture and probe both liquid (originating from an MDI starting formulation or a nebulizer starting formulation) and solid particles (from a DPI starting formulation), (2) the conditions (relative humidity and temperature) that the levitated droplet experiences can rapidly be changed, (3) relative humidities greater than 99.5% are readily accessible. Taken together, these features directly mimic the conditions an inhaled aerosol experiences while simultaneously monitoring changes in particle size/structure.
Saturation is reached in the trap through creating a temperature gradient across the trapping region through independently controlling the temperature of each electrode with a Peltier cooler. The effect of changing the magnitude of the temperature gradient on water droplet evaporation is tailorable such that a relative humidity at saturation is readily reached.
This new trap is coupled with the a recently developed method to extract particle structure from light scattered from the droplet (termed a phase function). Together, these techniques allow for the detailed kinetic measurements of both droplet drying and dissolution to be reported.