Comparing the dynamic flow properties and compaction properties of pharmaceutical powder mixtures

The dynamic flow properties and compaction characteristics of mannitol and mannitol-sodium carbonate mixtures (80/20, 70/30 and 60/40 by mass) were measured using a Freeman FT4 powder rheometer. The results showed that the mixtures containing up to 30% sodium carbonate had better flow properties and improved compaction characteristics when compared with mannitol alone. The study demonstrated the feasibility of combining a more expensive pharmaceutical excipient with a cheaper ingredient, without compromising desired powder characteristics. It may also provide a useful method for assessing the suitability of new formulations for use as direct compression bases, as part of a wider range of powder flow tests

Measuring the flow properties of small powder samples using an avalanche tester

The feasibility of using a small-scale avalanche tester to measure the flow properties of pharmaceutical lactose powders was examined. The modes of behavior observed in larger systems were displayed and showed a clear distinction between angular, free-flowing particles and more spherical particles of similar flow characteristics. Angular Lactohale LH100 particles showed slumping behavior at a rotational frequency of 0.33 Hz that disappeared at higher frequencies. Spherical lactose powder with a similar flow function to LH100 only showed rolling behavior under the same conditions, as did more cohesive powders LH200 and LH300. Further investigation of the LH100 data using fast Fourier analysis showed that the slumping frequency was one tenth of the rotational frequency