The effects of high shear blending on alpha-lactose monohydrate.

alpha-Lactose monohydrate is an important pharmaceutical excipient used extensively in dry powder inhaler (DPI) formulations. The ways in which a high shear blending process affect this material have been investigated and important process parameters have been identified. Total energy input (kJ/kg), blade design and the conditions in which lactose was stored prior to blending were found to have the most significant effect on the apparent particle size distribution of the processed material, which may subsequently affect the performance of DPI formulations. The power conditions used during blending, equipment temperature and humidity of the headspace above the powder were found to be less important in this respect. Additionally, it was found that high energy blending could induce changes in the water sorption characteristics of the material, although the formation of amorphous material could not be confirmed.