Formulation, characteristics and aerosolization performance of azithromycin DPI prepared by spray-drying

In this study, a number of dry powder formualtions of azithromycin for inhalation were designed to optimize the composition and further explore the relationship between the composition, the physical properties and the aerosolization performance, hence developing a dry powder inhalation (DPI) of azithromycin (AZI) as an alternative to its counterpart nebulizer. Dry powders of azithromycin with a variety of carrier types and carrier:drug ratios were prepared by spray-drying and characterized afterwards for different physical properties, including particle size and distribution, morphology, flowability, powder density and hygroscopic nature. In-vitro deposition was also evaluated after the aerosolization of powders at 60 L min− 1 via the Aerolizer® into a twin-stage liquid impinger (TI). It was found that the type and amount of the carrier had significant effects on the aerosolization performance of DPI. The results also showed that the particle size and flowability were two critical physical properties responsible for the aerosolization performance. Specifically, moderate particle size around 5–6 µm produced relatively high respirable fractions (RF). In terms of the flowability, the angle of repose within the range of 43°–52° was in a good linear relationship (r = 0.9523) with the RF value. In particular, the addition of L-leucine with the carrier:drug ratio of 1:5 showed the highest RF at 37.5%, which indicated that L-leucine is a promising carrier for the dry powder formulation of AZI for inhalation.