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Penetration of Fluoroquinolone Antibiotics in the Rabbit Cornea as Detected by Confocal Microscopy

¹ Ophthalmology, Univ of California - Irvine, Irvine, CA, United States

Commercial Relationships: B.J. Reiser, None; R.S. Chuck, None.

Abstract

Purpose. To detect penetration of fluoroquinolone antibiotics in ex vivo rabbit corneas by measuring excited fluorescence induced at 488nm using confocal microscopy.
Materials and Methods. 25 New Zealand White rabbit eyes were enucleated and the corneas prepared for treatment within 6 hours of sacrifice. The eyes were treated with the following solutions: balanced salt solution (BSS, Alcon Laboratories, Fort Worth, TX) which served as a control, ciprofloxacin (0.3 %) (Ciloxan, Alcon Laboratories, Inc.), ofloxacin (0.3%) (Ocuflox, Allergan, Inc., Irvine, CA), gatifloxacin (0.3%) (Allergan, Inc., Irvine, CA), and levofloxacin (0.5%) (Quixin, Santen USA, Inc, Napa, CA). Three drops of each were topically applied to the cornea and allowed to incubate for 5 minutes in a moist chamber maintained at 4 ° C. Another three drops were applied and allowed to sit for another five minutes. To rinse away excess antibiotic, each globe was washed with approximately 5 ml of lactated Ringer’s solution (Baxter Healthcare Corp., Deerfield, IL) prior to embedding in OCT and freezing in liquid nitrogen. Within 24 hours of freezing, 8µm sections were prepared and mounted for confocal microscopy. At an excitation wavelength of 488nm, the resultant fluorescent images were captured and recorded. All images were analyzed using a spectrometric program, LSM®, and all data analysis was performed using the Microsoft Excel ® spreadsheet program.
Results. Based on the observed fluorescence in the full thickness cornea induced at an excitation wavelength of 488nm, all antibiotic-treated sections showed penetration of the fluorescent fluoroquinolone into greater than 80% of the total depth of the epithelium. Ciprofloxacin penetrated into 84 +/- 6.5%, ofloxacin penetrated into 92.3 +/- 3.0%, gatifloxacin penetrated into 92.4 +/-2.7% , and levofloxacin penetrated into 95.2% +/-2.4% of the epithelium. Peak fluorescence intensities of the fluoroquinolones in the stroma did not significantly rise above background intensity.
Conclusions. In ex vivo rabbit cornea, fluoroquinolone antibiotics penetrate through most of the epithelium without significantly penetrating the stroma.

Keywords: cornea: basic science • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • animal model

© 2003, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any part of this abstract, contact the ARVO Office at arvo{at}arvo.org.