Use of the Revolution Powder Analyzer as a tool to measure the flowability of lactose suitable for direct compression

This poster has been presented at the 15th World Meeting on Pharmaceutics, Biopharmaceutics and Pharmaceutical Technology, which took place in Prague, Czech Republic.

Objective

The aim of this study is to compare the flowability of different types of lactose using the Revolution Powder Analyzer. This instrument enables to evaluate the flowability of powders in a dynamic state 1 with low stress 2 such as the state of the powder during die filling in the tablet press. Good flowability is a requirement for efficient and reproducible die filling enabling consistent tablet weight and API content uniformity 3.

Materials and Methods

Excipients

Granulated lactose : EXCIPRESS TM GR150 (Armor Pharma)
Spray-dried lactose : EXCIPRESS TM SD2L (Armor Pharma)
Sieved lactose : ARMOR PHARMA TM lactose monohydrate 80M
Milled lactose : ARMOR PHARMA TM lactose monohydrate 150M, 200M, 350M and 450M

Revolution Powder Analyzer

Figure 1. Avalanche of powder using the Revolution (Mercury Scientific Inc)

An identical volume of powder is placed in a rotating drum. When the powder turns in the drum, it provokes an avalanche 1 which is shown on the 3 pictures (Figure1). The analysis of avalanches is done with an image software.

For this study, two measurements were selected:

The break energy (mJ/kg) that represents the amount of energy required to start each avalanche.
The surface fractal calculated by the software. It provides an indication of how rough the surface of the powder bed1 is (from 1 to 11). The calculation is done after each avalanche, and it determines how the powder reorganizes itself.

Results

Lactose Characterization and Flowability

The break energy of granulated, spray-dried and sieved lactose are lower versus milled lactose (Table 2) indicative of a higher flowability1. There is a correlation between the size of the particles and the flowability of the powder. Larger particles of powder shows higher flowability as Van der Walls forces are less dominant1.

Surface fractal

If the powder forms a smooth and even surface, the surface fractal will be close to 2. If the surface is rough, the surface fractal will be greater than 5.

Granulated and spray-dried lactose have a surface fractal close to 2 (Figure 2). It means that these lactose grades could be directly used on the tablet press. They are ready-to-use for direct compression.

Sieved lactose presents a surface fractal between 2 and 5 (Figure 2). This lactose is made of coarse particles so it is not recommended for compression.

The different grades of milled lactose have a surface fractal greater than 5 (Figure 2) so milled lactose could not be used directly on the press. It needs to be granulated or spray-dried.

Conclusion

The Revolution Powder Analyzer enables to select the lactose that could be used for direct compression. This is done by the calculation of the surface fractal that represents the surface roughness of the powder bed after an avalanche. This parameter gives an indication of the way the filling of the powder into the die of the tablet press will be done. It could be used as a quick feasibility test for excipient characterization during product development.

See the full poster on Use of the Revolution Powder Analyzer as a tool to measure the flowability of lactose suitable for direct compression here

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Source: Amor Pharma, M. CHARBAUT, A. PERRIN, L. KERRIOU, PBP poster: Use of the Revolution Powder Analyzer as a tool to measure the flowability of lactose suitable for direct compression