Development of a new formulation of roflumilast for pulmonary drug delivery to treat inflammatory lung conditions

The aim of this study was to develop roflumilast dry powder inhaler (DPI) formulations by spray drying using hydroxypropyl-β-cyclodextrin (HPβCD) and to determine their suitability for pulmonary delivery. Different feed solution concentrations, solvent systems and spray drying parameters were used to obtain the formulations which were characterized using X-ray powder diffraction, thermal analysis, scanning electron microscopy, particle size distribution, bulk and tapped density, specific surface area, dynamic vapour sorption, in vitrodeposition properties using a Next Generation Impactor (NGI) and transepithelial permeability. Microparticles spray dried from ethanol were wrinkled and amorphous, exhibiting high glass transition temperatures while those from methanol:n-butyl acetate consisted of irregularly shaped porous particles partially crystalline. All formulations presented low density, particle size and residual solvent content exhibiting high depositon in the lower stages of the NGI. Mass median aerodynamic diameters (MMADs) were in the range of 3.32–4.49 μm, with high fine particle fractions (FPF < 5 μm). Stability studies demonstrated no significant modifications in the solid-state nature and in the aerolisation performance of the selected formulation which presented a Papp of 8.73 × 10−6 ± 4.70 × 10−7 cm/s. The developed roflumilast DPI formulations have potential therapeutic applications in the treatment of lung diseases.