Inhaled anti-infective drugs play a pivotal role in the prophylaxis and treatment of respiratory tract infections. In this study, fluoroquinolone antibiotic levofloxacin hemihydrate-loaded PLGA microparticles were prepared and evaluated. PLGA microparticles were prepared using three different preparation methods such as oil-in-water (o/w), water-in-oil-in-water (w1/o/w2) and modified water-inoil- in-water (w1/o/w3) emulsion solvent evapora-tion methods. Effects of preparation methods and formulation parameters on physicochemical properties of mic-roparticles characterized in terms of the particle size, encapsulation efficiency, production yield, in vitro release and aerodynamic properties were evaluated. Particle size results showed that the increasing volume of dichloro-metane in the organic phase caused a significant decrease in particle size of microparticles. Microparticles prepared by using o/w emulsion solvent evaporation method showed a higher encapsulation efficiency value compared to those prepared with double emulsion methods. Biphasic extended-release profile was produced in vitro. All for-mulations prepared except of F1 coded formulation were of suitable aerodynamic size for inhalation having a mass median aerodynamic diameter less than 5 μm. These results showed that levofloxacin hemihydrate-loaded PLGA microparticles could be a potential alternative to the existing levofloxacin therapy in respiratory tract infections.

Keywords: PLGA microparticles, Emulsification methods, Levofloxacin hemihydrate, Respiratory tract infections, Pulmonary delivery