Effect of geometric structure of flow promoting agents on the flow properties of pharmaceutical powder mixture.

PURPOSE

The object of this work was to investigate the mechanism of how the surface geometric structure of flow agents affects on the flowability of pharmaceutical powder mixtures.

METHODS

Nonporous and porous silicas were mixed with directly compressible fillers as flow promoting agents. The geometric structure of flow agents was investigated by gas adsorption and laser diffraction analysis. Flowability was evaluated with Carr's index measurement. Adhesion force between fillers and flow agents was determined using atomic force microscopy.

RESULTS

Flowability was improved with the addition of both nonporous and porous flow agents. In the case of nonporous flow agents, effect to promote flowability decreased with the increase of particle diameter, whereas porous flow agents highly improved flowability independent of particle diameter. Atomic force microscopy measurement found that the adhesion force between a porous agent and filler was smaller than that between a nonporous agent and filler.

CONCLUSIONS

Enhancement of flowability varies depending on the geometric structure of flow agents. Porous flow agents improve flow properties more than nonporous agents, because porosity is highly contributed to reduction of adhesion force between particles.