Corneal stromal penetration of topical ciprofloxacin in humans

Use of fluoroquinolone agents as single drug treatment for severe bacterial keratitis requires that adequate stromal drug concentrations are achievable that exceed the MIC90 for common corneal pathogens. The purpose of this study, therefore, is to document the human stromal penetration of the fluoroquinolone, ciprofloxacin, in human tissue obtained from patients undergoing penetrating keratoplasty.

Twelve patients, all with intact corneal epithelia, received 0.3% ciprofloxacin (Ciloxan) eyedrops every 15 minutes for the first hour and then every hour for 10 hours before their scheduled keratoplasty. Corneal tissue samples obtained from the excised buttons at the time of surgery were frozen and subsequently analyzed for drug concentration using high-pressure liquid chromatography.

A mean corneal tissue concentration of 5.28 +/- 3.4 micrograms/g tissue (mean +/- standard deviation) of ciprofloxacin was determined. Tissue levels ranged from 1.43 micrograms/g of tissue to 10.58 micrograms/g of tissue.

Ciprofloxacin penetration was variable in patients with an intact epithelium and, in some cases, did not exceed the MIC90 for some gram-positive organisms. The presence of an epithelial defect is expected to potentiate the penetration of ciprofloxacin to most likely exceed the MIC90 for most corneal pathogens.