Optical diagnostics studies of air flow and powder fluidisation in Nexthaler®. Part II: Use of fluorescent imaging to characterise transient release of fines from a dry powder inhaler

Abstract

The fine particle fraction is a key indicator of therapeutic effectiveness of inhaled pharmaceutical aerosols. This paper presents a fluorescence imaging technique to visualise and characterise the emission of active pharmaceutical ingredient (API) fines in model formulations containing coarse lactose carrier and 1.5-2 μm diameter fluorescent microspheres (model API fines). A two-camera arrangement was used to acquire simultaneous images of spatial and temporal distribution of model API fines and fluidised powder formulation near the mouthpiece exit of a DPI. Digital image analysis showed that the model API fines were released along with the bulk of the powder dose. More rapidly accelerating airflows were found to cause earlier release of API fines. The fluorescence imaging technique analyses a substantial fraction of the aerosol plume and was found to provide effective time-resolved characterisation of the de-aggregation and release of API fines with consistent results across a wide range of model API concentrations. Future studies should demonstrate the usefulness of the fluorescence imaging technique across different formulations and DPI devices.

Modelling Deaggregation Due to Normal Carrier–Wall Collision in Dry Powder Inhalers

“…Particle Image Velocimetry (PIV) has been used to obtain instantaneous velocity measurements of the fluid flow in Processes 2022, 10, 1661 2 of 25 DPI [10][11][12]. High-speed photography measurements have been applied to study carrier motion [11,13] and API-carrier detachment phenomena [14] in specially designed transparent DPI.…”

Effect of inflow conditioning for dry powder inhalers

“…In general, the device design, drug formulation, and inhalation characteristics are the main controlling parameters [6,7,8,9,10,11]. Many available studies have used commercially available DPIs with a fixed design to shed light on the influence of the above parameters on DPI effectiveness [12,13,14,15,16,17,18]. Recently, the effect of powder properties has been summarized by Mohammad et al in their study of high dose delivery inhalers concerning tuberculosis treatment [19].…”

WITHDRAWN: 3D characterisation of dry powder inhaler formulations: Developing X-ray micro computed tomography approaches

“…Microstructure can also be assessed when studying the fluidisation and ease of dispersion of cohesive DPI powders. Particle image velocimetry (PIV) [18] and fluorescent imaging [41] employ 2D cameras to study the flow velocity and spatial distributions of API fines respectively while LD airflow titration experiments have also been employed to study the ease of de-agglomeration [5,25]. However, cohesiveness is only an indirect indicator of the microstructure.…”