Kotoe Ohta

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

AbstractPurpose. 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 Carrs 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.

Effect of geometric structure and surface wettability of glidant on tablet hardness

The aim of this study is to investigate the effect of geometric structure and surface wettability of glidant on tablet hardness. Geometric structure is defined, in this work, as three-dimensional structure such as porosity, particle size and specific surface area. A variety of silica was incorporated in direct compressive fillers as glidant and mixed powder was compressed in single punch tablet machine with and without 0.5 wt.% magnesium stearate. Flowability of mixed powder was evaluated with Carrs index measurement. In the case of unlubricated compression, tablet hardness decreased as a function of additional concentration of silica. Reduction rate directly depended on surface coverage of silica over filler surface and hydrophobicity. Since surface coverage is related to geometric structure, it can be concluded that structural influence plays an important role to determine tablet hardness. While, in the case of lubricated compression, either water adsorption amount or geometric structure effects on tablet hardness. Increase of tablet hardness was observed only when hydrophilic porous and small size nonporous silica were added. All the other silica had deleterious effect on tablet hardness and in particular hydrophobicity strongly reduced tablet hardness.