Accuracy assessments for laser diffraction measurements of pharmaceutical lactose

Abstract

The accuracy of laser diffraction size measurements of dry powder inhaler particles, which play an important role in guiding effective inhaler system design, is assessed. Additionally, data for lactose particle shape characteristics are presented. Comparisons made between microscopy and cohesion-minimized laser diffraction size measurements for pharmaceutical lactose particles indicate that non-sphericity causes a broadening of the size distribution while the median diameter is unchanged. This is corroborated by data in the literature. Poured particles and those dispensed from an inhaler shared a common characteristic agglomerate modal diameter that was absent in the cohesion-minimized wet suspension. It is concluded that the interpretation of integral measurements of the particle size distribution using laser diffraction, for cohesive particle systems, is reasonable. The method of dispensing particles from an inhaler and delivery through an artificial throat is critical and both decreased the proportion of agglomerates present.