Fine Particle Profile of Fluticasone Propionate/Formoterol Fumarate Versus Other Combination Products: the DIFFUSE Study

The efficacy of inhaled products is affected by the degree, and potentially the site, of drug particle deposition in the lungs. Lung deposition correlates with the fine particle fraction (FPF; the proportion of dose containing particles <5 μm in aerodynamic diameter). This in vitro study (defining fluticasone propionate/formoterol particulate size [DIFFUSE]) examined the effects of inhalation flow rate on the FPF of the fluticasone propionate/formoterol (FP/FORM) pMDI aerosol compared with three other inhaled corticosteroids/long-acting β2-agonist (ICS/LABA) combination therapies administered by either DPI or pMDI [fluticasone propionate/salmeterol (FP/SAL), budesonide/formoterol (BUD/FORM) and beclometasone dipropionate/formoterol (BDP/FORM)]. Aerodynamic particle size distribution was determined for each product using an 8-stage Andersen Cascade Impactor at two inhalation flow rates: 28.3 and 60.0 L/min. Fine particle dose (mass of dose <5.0 μm) and FPF were calculated as a percentage of the labeled dose for the LABA and ICS of each product at both flow rates. FP/FORM suspension aerosol provided a high and consistent FPF of approximately 40% for the ICS and LABA components at both flow rates. At 28.3 L/min, the FPF of each component of FP/FORM (41.2% and 39.2%) was greater than that of FP/SAL DPI (12.5% and 11.3%), BUD/FORM DPI (8.2% and 6.6%) and BDP/FORM pMDI (28.5% and 26.0%). At 60.0 L/min, the FPFs of the FP/FORM components (43.7% and 42.1%) were greater than those of FP/SAL (17.8% and 14.8%) and BUD/FORM (35.0% and 30.1%), and similar to those of BDP/FORM (43.0% and 39.5%). The FP/FORM suspension aerosol produced a high and consistent FPF of approximately 40% across both flow rates. The consistent FPF in vitro may be predictive of FP/FORM providing more consistent drug dosing in vivo, helping to counteract variable lung dose due to variation in inspiratory flow rate among patients and between a patient's day-to-day or successive inhalation maneuvers.