The role of capsule aperture size on the dispersion of carrier-based formulation at different air flowrates

The effect of capsule aperture size on the aerosol performance of lactose blend formulation was studied using Foradil (R) (containing 12 mu g of formoterol fumarate (FF1) and 24 mg of lactose) dispersed with a powder inhaler Aerolizer (R) at increasing air flowrates. Apertures sizes of 0.4, 1.0, 1.5, 2.5, and 4.0 mm were introduced at the opposite ends of the capsule. The formulation was dispersed into a Next Generation Impactor (NGI) at 30, 60 and 90 L/min, with the fine particle fractions (FPFrec and FPFem) measured by chemical assay of FF and lactose using high-performance liquid chromatography. Particle size distribution (PSD) of FF particles dispersed in wet media was also characterized by laser diffraction. FPFrec showed a stronger dependency on the flowrate than the capsule aperture size. The most efficient dispersion was achieved at 90 L/min. At a given flowrate, FPFem remained broadly constant across different aperture sizes. The laser diffraction studies demonstrated the presence of large agglomerates.