The effectiveness of two ciprofloxacin formulations for experimental Pseudomonas and Staphylococcus keratitis

Ciprofloxacin is a fluoroquinolone antibiotic with broad spectrum bactericidal activity. A commercially available form of ciprofloxacin contains benzalkonium chloride (BAC) (0.006%) and EDTA (0.05%) as preservatives. Since BAC has been shown to cause adverse changes in corneal epithelial cells, a formulation of ciprofloxacin devoid of BAC and EDTA but with the same effectiveness would be valuable. We present here the results of experiments designed to assess the efficacy of a BAC-free and EDTA-free formulation of ciprofloxacin, Ciprofloxacin-polystyrene sulfonate (PSS), in experimental models of Pseudomonas aeruginosa and Staphylococcus aureus keratitis. Both formulations of ciprofloxacin sterilized corneas infected with P aeruginosa, and both formulations showed equal bactericidal activity for S aureus. Normal eyes treated with either formulation showed mild conjunctival irritation compared to untreated normal eyes. The bactericidal activities of both formulations of ciprofloxacin were excellent. Therefore, the Ciprofloxacin-PSS formulation could serve as an effective single drug therapy for ocular infections.