Spray drying of budesonide, formoterol fumarate and their composites—I. Physicochemical characterisation

The objective of this work was to examine the physicochemical properties of spray dried budesonide, formoterol fumarate and their mixtures at two different weight ratios: 100:6 and 400:6 of budesonide and formoterol fumarate, respectively. A comparison of the thermal properties, crystalline/amorphous nature and particle size of the starting micronised as well as processed materials was carried out. The micronised drugs on their own and the physical mixtures were crystalline in contrast to the spray dried counterparts which were shown to be amorphous. The glass transition temperatures (Tgs) of the processed actives were determined and appeared at 89.5 and 88 °C for budesonide and formoterol fumarate, respectively. As for the spray dried composites, an indication of miscibility and/or interactions between the components was indicated by differential scanning calorimetry and infrared analysis. The spray drying in all cases resulted in smooth, spherical microparticles of sizes suitable for inhalation.