Effect of particle size, air flow and inhaler device on the aerosolisation of disodium cromoglycate powders

Recently, the dispersion of mannitol powders has demonstrated the importance of particle size, air flow and inhaler device ( Chew and Chan, 1999). The aim of the present study is to extend our investigation to a different compound, disodium cromoglycate (DSCG) powders. Solid state characteristics of the powders were assessed by particle sizing, scanning electron microscopy, X-ray powder diffraction, moisture content, particle density determination and freeze fracture. The aerosol behaviour of the powders was studied by dispersion using Rotahaler® and Dinkihaler®, connected to a four-stage liquid impinger operating at 30–120 l/min. Three amorphous powders with a mass median diameter (MMD) of 2.3, 3.7, 5.2 μm and a similar polydispersity were prepared. The particles were nearly spherical with a particle density of 1.6 g/cm 3 and moisture content of 6.6 wt.%. Using Rotahaler®, the maximum fine particle fraction (FPF max) for all three powders was only 15 wt.%, attained at the highest flow of 120 l/min. Using Dinkihaler®, the FPF max was two to four times higher, being 36 and 29 wt.% for the 2.3 and 3.7 μm powder, respectively, at 60 l/min; and 18 wt.% for the 5.2 μm powder at 120 l/min. Hence, the study shows that the FPF in the DSCG powder aerosols was determined by the interaction of the particle size, air flow and inhaler design. The attribution of the amorphous nature and the different physico-chemical properties of the powder may explain the incomplete and low dispersibility of DSCG.