The effect of V-mixer scale-up on the mixing of magnesium stearate with direct compression microcrystalline cellulose

The effect of V-mixer size on the mixing of magnesium stearate with directly compressible microcrystalline cellulose is reported. The mixers used were geometrically similar with a seven-fold difference in tile volumes of the smallest (320 cm(3)) and biggest mixer (2250 cm(3)). To evaluate the mixing process and compare the performance of the mixers, the extent of the decrease in tablet crushing strength was measured. The kinetics of the decrease in crushing strength were best described by the sum of two separate processes, one first-order and the other second-order. Overall, the faster second-order process dominated mixing because the first-order rate decreased, while the second-order rate increased, with an increase in mixer volume. Results show that the limiting crushing strength increased with an increase in miser size and that there was a linear relationship between the limiting crushing strength and the logarithm of the volume of the mixer. A decrease in mixer load from 33 to 18%, also led to an decrease in tablet strength. The results can be used to scale-up the lubricant mixing process in V-mixers. (C) 1997 Elsevier Science B.V.