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Estimating Aerosol Size Distributions and Doses Entering the Trachea

Byron PR, Wei X, Bormann K.

Respiratory Drug Delivery 2016. Volume 1, 2016: 109-116.

Abstract:

Predicting total lung dose in vitro (TLD_in vitro) from inhalers, based on experimental estimates of the aerosol drug mass exiting mouth-throat (MT) models during realistic breath profile testing, provides values for TLD_in vitro that can be correlated with clinical measurements of TLD_in vivo. In the event that aerodynamic particle size distributions (APSDs) can also be determined for the aerosol drug dose exiting these models (APSD_TLDin vitro), it may be possible to compare distributions between inhalers and/or to project possible regional drug distribution in the lung using modeling. Presently however, realistic testing for the dry powder inhalers (DPIs) that will likely dominate our markets in years to come, frequently requires the use of inhalation profiles (IPs) with peak inhalation flow rates (PIFRs) > 100 L/min, the maximum flow rate at which cascade impactors suitable for pharmaceutical use have been calibrated. By coupling our proposed realistic test methods for powder inhalers to constant flow rate cascade impactors employing the Next Generation Pharmaceutical Impactor (NGI), via a Nephele Mixing Inlet (NMI) and air supply, we explored the possibility that realistic IPs could be employed in a modified NGI with airflow set to 140 L/min, to determine APSD_TLDin vitro for drug aerosols from a proprietary inhalation drug product, Budelin^® Novolizer^®.