Impact of Vehicle Composition on Solubility, Autoclave Sterilization Stability, and Antibacterial Activity of Ciprofloxacin Hydrochloride Ear Drops

This research focused on the formulation of ciprofloxacin hydrochloride ear drops for the treatment of acute otitis externa, caused by pathogens such as <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i>. The study aimed to enhance the solubility of ciprofloxacin at physiological pH and improve its stability during autoclave sterilization by employing polyalcohol vehicle systems composed of deionized water, glycerin, and propylene glycol. Formulations containing 0.33% <i>w</i>/<i>v</i> ciprofloxacin HCl were evaluated for solubility within a pH range of 4.0 to 7.0 and underwent autoclave sterilization to assess their chemical stability and antibacterial efficacy. Following sterilization, the formulations were stored at 25 °C in amber containers for a duration of 180 days. High-performance liquid chromatography (HPLC) was utilized to evaluate chemical stability, while antibacterial activity was determined using the disk diffusion method. The results demonstrated that glycerin and propylene glycol effectively inhibited ciprofloxacin precipitation at physiological pH. The ciprofloxacin content decreased by less than 3.58% while preserving antimicrobial efficacy against <i>S. aureus</i> and <i>P. aeruginosa</i>. Both formulations retained over 90% of their labeled drug content, indicating a minimum shelf life of 180 days under the specified storage conditions.