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Published on: April 6, 2017
Entrainment of lactose inhalation powders: a study using laser diffraction
C P Watling1, J A Elliott, R E Cameron
1Pfizer Institute for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, CB23QZ, UK.
Summary
Investigating powder entrainment mechanisms in dry powder inhalers reveals that increasing fine particles alters powder flow from erosion to fracture. This impacts aerosolization efficiency and powder delivery.
Area of Science:
- Pharmaceutical Sciences
- Materials Science
- Chemical Engineering
Background:
- Dry powder inhalers (DPIs) rely on precise powder aerosolization for effective drug delivery.
- Understanding powder entrainment mechanisms is crucial for optimizing DPI performance.
- Lactose is a common carrier excipient in DPI formulations.
Purpose of the Study:
- To investigate the entrainment mechanisms of lactose inhalation blends using laser diffraction.
- To determine how added fine particles influence powder entrainment behavior.
- To correlate powder flowability with entrainment mechanisms and aerosolization characteristics.
Main Methods:
- Utilized a diffraction particle size analyzer (Malvern Spraytec) to analyze powder entrainment.
- Compared transmission data with particle size information to differentiate between erosion and fracture mechanisms.
- Employed an annular ring shear tester to measure powder flowability.
- Investigated lactose blends with varying weight percentages (wt%) of added fine particles (0%, 5%, 10%).
Main Results:
- Entrainment mechanism shifted from mild fracture (multiple small plugs) to severe fracture (fewer, larger plugs) with increased fine particle content.
- Severe fracture included single-plug emptying or delayed emptying due to sticking.
- Fracture severity was inversely proportional to powder flowability.
- Higher fine particle volume led to a smaller fraction of aerosolized fines, attributed to dispersion behavior.
Conclusions:
- Laser diffraction provides detailed insights into inhalation powder entrainment beyond simple particle size distribution.
- Fine particle content significantly alters entrainment mechanisms, impacting powder flow and aerosolization in DPIs.
- Powder flowability is a key factor influencing entrainment severity and aerosolization efficiency in lactose-based DPIs.
