New proportion of levofloxacin citrate: Structural, physicochemical properties, and potency studies

Stability and potency improvement have been reported by reacting levofloxacin (LF) with citric acid (CA) in a (1:1) molar ratio. However, CA is known to be irritant to the gastrointestinal tract and should be minimized. In a novel approach, this experiment aimed to prepare LF - CA salt with reduced CA, the (2:1) molar ratio, study the structure, and investigate its solubility, stability, and potency improvement. Solvent-dropped grinding and slow evaporation methods were used to prepare the new ratio composition salt, characterized by electrothermal, differential scanning calorimetry, and powder X-ray diffractometry to confirm the physically new solid-state formation. Next, Fourier transform spectrophotometry identified the chemical interaction between LF and CA. After that, a comprehensive structural study using single-crystal X-ray diffractometry determined the 3D structure of the new salt, which determined the solid physicochemical behavior. Finally, stability, solubility, and potency tests were done to investigate the benefits of the new LF-CA composition. As a result, this experiment successfully synthesized the salt, which bound 4.5 water molecules, named LFCA (2:1) - 4.5 hydrate. This new solid-state salt was comparable with the established (1:1) molar ratio in solubility, stability, and potency, higher than LF alone. Hereafter, with a reduced CA portion, this new composition holds potential for further development in drug formulation as a stable, safer, and more efficient antibiotic.