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Dynamic avalanching accurately assesses flowability and quality.

Article Excerpt
The amount of fine ([less than or equal to]10[micro]m) particles in bulk antibiotics can be source of problems during the production of finished dosage forms as they can be subjected to forces of agglomeration and/or cohesion, resulting in poor powder flow and non-uniform drug dispersion in a formulation blend. Dynamic avalaching measurements were conducted on samples of the antibiotic Cefaclor. The surface fractal, or fractal dimension, progressively increased from the sample with the lowest specific surface area value to that with the highest, and this finding can be related to a progressive increase in powder surface roughness resulting from the corresponding increase in the amount of fine particles in the tested samples. This suggests the possibility of using fractal dimension values instead of specific surface area measurements to assess the suitability of Cefaclor samples for tablet formulation.

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Cefaclor is a [beta]-lactam cephalosporin antibiotic that has a wide particle size distribution. Because of the non-porous nature of the material, the specific surface area value accounts for a significant amount of fine particles possibly present in the samples under analysts. In light of this, dynamic avalanching measurements were performed on cefaclor samples characterized by comparable particle size distribution curves, but different specific surface area values.

What is dynamic avalanching?

Dynamic avalanching is a technique for investigating powder flow properties under dynamic conditions and has, in the last decade, received growing attention from the scientific community. (1), (2) Powder avalanching in a rotating drum enables the evaluation of dynamic powder flow characteristics on the basis of deterministic chaos theory. (3)

In the last few years, the commercial availability of automated powder flowability analysers has contributed to the widening acceptance of this analytical technique in the pharmaceutical industry. (4), (5) The first instrument launched on the market, AeroFlow (TSI Inc. Particle Instruments/Amherst, MA, USA), was based on a rotating plexiglas drum that contained the powder to be tested. The powder movement was monitored by a light and photocell arrangement; the photocell, located behind the drum, collected the light passing through the drum and recorded light variations resulting from cyclic formation of avalanches. Kaye has reported the theoretical basis for this commercial device. (3),...

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