The present paper examines the effects of processing variables and lubricant content on the hydrophobicity of pharmaceutical blends. A novel shear cell is used to process blends, with different lubricant concentration, using different combinations of shear rate (i.e. rpm of the cell) and strain (i.e. length of exposure). The hydrophobicity of blends is measured using Washburn technique.

The results show that lubricant content and strain are the main parameters affecting blend hydrophobicity. Shear rate also affects it, for large values of strain. The results of the entire methodology (processing of lubricated blends and analytical technique to measure hydrophobicity) are highly reproducible, and the error associated is measured for all the experimental conditions explored.

We conclude that the Washburn technique is ideal to perform hydrophobicity measurements in the range expected for any lubricated pharmaceutical blend. Lubricant content and strain are key variables for the product properties.