Experimental observations of dry powder inhaler dose fluidisation

Lactose characteristics and the generation of the aerosol

“…Two lactose powders containing different proportions of fines (6% and 16%) exhibited a fracture mechanism during fluidisation that resulted in large agglomerates breaking off from the powder bed as it cracked along lines of weakness [47]. Of course, the porosity of the powder, which is the ratio of the volume of all voids in a powder bed to the total volume, provides a measure of the ease with which a flow can move through a stationary powder bed: the higher the porosity, the more void space is available for the air to flow through [47]. A direct correlation of particulate interaction with the aerosol performance is difficult because of the heterogeneous nature of both the drug and carrier surfaces (see Section 2.2.2) and assumptions with respect to force measurement.…”

The relationship between drug concentration, mixing time, blending order and ternary dry powder inhalation performance

“…The flowability of some of the formulations was, therefore, investigated. This was achieved through measurement of the angle of repose, as more advanced techniques, such as ring shear testing (Tuley et al, 2008) or powder rheometry (Shur et al, 2008), incorporate a preshear or conditioning stage, which might have obliterated any structural differences between formulations produced using different blending orders. In addition, these techniques would have required the manufacture of a greater amount of formulation than was permitted by the available salbutamol sulphate supply.…”

An Investigation into the Effect of Fine Lactose Particles on the Fluidization Behaviour and Aerosolization Performance of Carrier-Based Dry Powder Inhaler Formulations

“…The increased energy from these collisions enhances API resuspension (12). Whilst studies by Versteeg et al, and Tuley et al, have shown similar observations (13,14), Shur et al, related the different fluidization mechanisms for powder beds with high and low fines content to powder flow measurements performed using powder rheology (12). These findings suggest the specific relevance of the Geldart classification in defining the mechanism by which the addition of relatively small concentrations of lactose fines (Geldart group C powders) can directly affect the fluidization properties of an aeratable coarse lactose (Geldart group A powder).…”