Antibacterial activity of the white precipitate formed on the corneal surface after treatment with ciprofloxacin ophthalmic solution

Purpose, To determine the antibacterial activity of the white crystalline p recipitate formed on the corneal surface after topical administration of 0. 3% ciprofloxacin ophthalmic solution by microbiologic assay. Methods. White crystalline precipitate formed on the corneal surface of seven patients wa s scraped and individually dissolved in sterile distilled water. Quantifica tion by high-performance liquid chromatography (HPLC) and microbiologic ass ay of ciprofloxacin in the precipitate solutions were done. Microbiologic a ssay was performed by agar diffusion method against Klebsiella pneumoniae. Results. By HPLC, concentrations of ciprofloxacin were estimated to be 1.5- 60 mu g/ml in the dissolved precipitate obtained from six patients, whereas the concentrations based on microbiologic assay varied from 1.6 to 16.1 mu g/ml. Ciprofloxacin was not detected by either method in the precipitate o btained from one patient. The antibacterial activity (mu g/ml) determined b y microbiologic assay was not related to the actual amount of ciprofloxacin in the solutions as estimated by HPLC in cases 1, 2, 4, and 7. It was almo st the same in the solutions from cases 5 and 6. Conclusion. The white crys talline precipitate formed on the corneal surface after topical administrat ion of 0.3% ciprofloxacin ophthalmic solution exhibited bacterial inhibitor y activity, indicating that the precipitate may function as a drug depot.