Development and Characterization of Spray-Dried Combined Levofloxacin-Ambroxol Dry Powder Inhaler Formulation

Background: This study explores the development and characterization of spray-dried composite microparticles consisting of levofloxacin (LVX, a broad-spectrum antibiotic), and ambroxol (AMB, a mucolytic agent that has antibacterial and antibiofilm properties), for the intended application of the drug against lower respiratory tract infections (LRTIs). Methods: A range of LVX to AMB mass ratios (1:1, 1:0.5, and 1:0.25) were prepared, with and without the use of the dispersibility enhancer leucine (LEU), and spray-dried following pre-optimized parameters to achieve the required particle size (1-5 µm) and flow properties. The formulations were characterized by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and a thermogravimetric analysis (TGA). The in vitro aerosolization performance of the new formulation was evaluated with a twin-stage impinger (TSI) at a flow rate of 60 ± 5 L/min. Using a validated RP-HPLC method, LVX and AMB were quantitatively determined. Results: The combined spray-dried LVX, AMB, and LEU particles were spherically shaped with sizes ranging from 1.9 to 2.9 µm, thus complying with the size requirements for effective deep lung deposition. The dispersibility enhancer leucine produced a high yield and enhanced the flow properties and aerosolization characteristics of the spray-dried formulations. The LVX to AMB mass ratios showed a remarkable impact on the aerosolization properties, with the LVX to AMB 1:1 mass ratio demonstrating the best flow and FPFs for both drugs. There must be a balanced ratio of these components for spray drying the composite particles to obtain composite particles of the required size and with the appropriate flow property. The addition of 5% of LEU significantly (p < 0.005) improved the FPF of all the formulations, probably by enhancing the surface hydrophobicity of the composite particles. Conclusions: The spray-dried combined antibiotics formulation has a strong potential for efficient lung delivery intended for the management of LRTIs.