Comparison of the particle size distribution of fluticasone propionate/formoterol and beclometasone/formoterol MDI using laser diffraction

Introduction: Fluticasone propionate/formoterol (FP/FORM; flutiform ® ; 125/5μg) has been shown to deliver a consistent median mass aerodynamic diameter (MMAD) and fine particle fraction (FPF), which were flow rate(FR)-independent (28.3-60L/min; MMAD: 3.15-3.52µm; FPF: 41%-44%) 1 . In contrast, the MMAD and FPF for beclometasone/formoterol (BDP/FORM; Foster ® MDI; 100/6µg) 1 , were FR-dependent (28.3-60L/min; MMAD: 0.50-1.21 µm; FPF: 29%-43%). To understand these results, the particle size distribution (PSD) of both were measured by Laser Diffraction (LD). Methods: Volumetric Median Diameter (VMD) was measured near the mouthpiece by LD to determine if BDP/FORM released larger particles than FP/FORM directly after actuation. Both pMDIs were actuated at ∼10cm from the laser beam. Due to their bimodal PSD, measurements were made with a flow-optimized throat to filter out particles >10µm. Results: Mean VMD (n=6/inhaler) was 3.4±0.07µm for FP/FORM and 4.2±0.14µm for BDP/FORM. The fine particle fraction (VMD Conclusions: The VMD for FP/FORM was similar to its published MMAD whereas the VMD for BDP/FORM was considerably larger than the reported MMAD. BDP/FORM had a significantly higher % of large particles, which are more likely to deposit in the throat, based on total mass compared to FP/FORM. These results may explain the FR-dependency seen with BDP/FORM and why FP/FORM has previously been shown to have a higher FPF than BDP/FORM at a low FR despite BDP/FORM having a smaller MMAD. 1 Johal et al Comp Prod Ther 2013;3:39-51 Sponsor: Mundipharma GmbH.