Effect on Addition of Light Anhydrous Silicic Acid to Drugs which are Different in Physical Properties by Particle Size etc

Pharmaceutical preparations such as sodium bicarbonate, lactose and potato starch show 2 different physical properties depending on their crystal diameters and moisture contents. Light anhydrous silicic acid (LASA) was added in several levels to 2 forms of the above preparations in order to investigate how these amounts of addition cause differences in their physical properties. Results are as follows: 1) The angle of repose was minimized when LASA was added to powdered sodium bicarbonate in a proportion ranging from 0.1 to 0.25% and became greater in proportions exceeding 0.25%. Both the angle of repose and apparent specific volume of crystalline sodium bicarbonate were minimized by addition of LASA 0.01% and became greater in proportions exceeding 0.5%. 2) In the case of powdered lactose, addition of LASA 0.01%resulted in negligible improvement in the physical properties. The effect was maximum in the proportion of 0.25%. In the case of crystalline lactose, addition of LASA even in 0.01% improved the physical properties. The effect was slightly enhanced by addition of LASA up to 0.1%. However, the addition of LASA in the proportion ranging from 0.25 to 0.5% deteriorated the effect. 3) The degree of improvement in the physical properties of wet and dry potato starch reached maximum by addition of LASA 0.25 and 0.05%, respectively. The effect on wet stacrch by addition of LASA was greater. 4) Scanning electron microscopy for observing the mixed conditions revealed that larger number of LASA particles attached to particles of the preparations when the physical properties were improved to a greater extent, and further increased proportions of addition resulted in the tendency to deteriorate physical properties by generation of aggregated particles of LASA attached particles of the preparations.