Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
238373 | Powder Technology | 2010 | 7 Pages |
This paper discusses how the hydrophobicity of lubricated pharmaceutical formulations is affected by process variables such as shear rate and strain. Hydrophobicity is a critical property that affects the dissolution of powder formulations, tablets and capsules as well as the performance of tablet coating and granulation operations. In this paper, hydrophobicity is measured using a modified Washburn method. Results show that, in the absence of lubricant, the hydrophobicity of powders does not change substantially as a function of shear rate or strain. However, when magnesium stearate is present (concentrations studied here range between 0.5% and 2%), hydrophobicity increases as a function of strain, shear rate and lubricant concentration. Observed changes range over several orders of magnitude, readily explaining common “overlubrication” observations of delayed drug dissolution.
Graphical abstractThis paper presents a method to quantify the effects of process variables (strain and shear rate) and magnesium stearate concentration (hydrophobic component) on powder blend hydrophobicity. This figure shows that a blend containing magnesium stearate increases its hydrophobicity Φ (Φ is the slope of linearized Washburn curves) when it is exposed to larger shear rates (rpm of the shear cell) and to larger strain (revolutions of the shear cell).Figure optionsDownload full-size imageDownload as PowerPoint slide