¹Department of Pharmaceutical Technology, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey DOI : 10.29228/jrp.136 This study aimed to design and characterize an inhalable dry powder of mometasone furoate monohydrate (MFM) combined with the formoterol fumarate dihydrate (FFD). Homogenization in water and spray drying processes were used to prepare the dry powders for inhalation. The physicochemical characteristics of the dry powders were evaluated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The particle size distribution, content uniformity, solid behavior and aerodynamic properties of DPI were also determined. After the micronization process, the particle sizes of the raw materials significantly decreased. SEM images implied that FFD covered the MFM surface during the spray drying step, and uniform particles were produced. X-ray and DSC results demonstrated that MFM did not show any change in crystal structure after homogenization and spray drying processes. DSC analysis of DPI formulation exhibited that the same melting point of MFM was observed when the drugs were spray dried. FT-IR spectra exhibited the characteristic peaks for MFM in DPI formulation. Content uniformity results showed that the developed production method is suitable for manufacturing uniform formulations. According to angle of repose, Hausner ratio and Carr’s index results, DPI formulation has preferable flow properties. In addition, emitted dose, mass median aerodynamic diameter, fine particle fraction showed that the DPI formulation could ensure drug delivery to the alveoli. This study showed that the combination of homogenization and spray drying methods is suitable to obtain a DPI formulation containing MFM and FFD with a particle size less than 5 μm to reach alveoli. Keywords : Mometasone furoate monohydrate; formoterol fumarate dihydrate; dry powder inhaler; asthma; combined drug therapy