Levofloxacin 1.5% safe for corneal endothelium

Key Points

Chicago-Intensive dosing with levofloxacin ophthalmic solution 1.5% (Iquix, Vistakon Pharmaceuticals) for 2 weeks did not demonstrate any adverse effects on the integrity and morphology of the corneal endothelium in humans, according to the study presented by Mark Abelson, MD, at the American Society of Cataract and Refractive Surgery annual meeting. All parameters evaluated in healthy human volunteers were almost identical to the mean baseline measurements after intensive dosing over a 2-week period.

Levofloxacin 1.5% was approved for treating patients with bacterial keratitis. A lower concentration, levofloxacin 0.5% (Quixin, Vistakon Pharmaceuticals) was approved for bacterial conjunctivitis. Bezwada et al. reported recently (Curr Med Res Opin. 2008;24:419-424) that in an in vitro study, the drug was the least cytotoxic of the fluoroquinolones to human corneal keratocyte and endothelial cell cultures. In an vivo study carried out by Clark and colleagues (Cutaneous Ocular Toxicol. 2004;23:1-18), wound healing was observed in rabbits and primates at a dose of two drops four times a day for 4 days. The investigators reported that there were no adverse effects on the cornea, re-epithelialization, keratocyte structure and organization, or wound healing, Dr. Abelson explained. He is associate clinical professor of ophthalmology at Harvard Medical School and senior clinical scientist at Schepens Eye Research Institute, both in Boston.

Effects on humans

The subjects were evaluated at baseline and on days 8, 15, and 21 (7-days post-dosing). The safety of the drug was tested after every 7 days of dosing and compared with baseline. The subjects were evaluated by specular microscopy for the endothelial cell density and the endothelial cell morphology, i.e., cell size variability and the percent of hexagonal cells. Pachymetry was performed to measure the central corneal thickness. Patients also were assessed by slit-lamp biomicroscopy and measurement of the visual acuity.

Study findings

All variables evaluated at baseline and after intensive dosing showed that levofloxacin did not affect any of the factors studied. Dr. Abelson reported that the mean endothelial cell density values measured at baseline and after dosing were virtually identical, that is, 2,767 ± 317 cells/µm² versus 2,786 ±295 cells/µm² , respectively. The sizes of the endothelial cells also were almost identical; the coefficient of variation at baseline and after dosing was 31.4 ± 5.2 versus 31.8 ± 5.9, respectively. The mean percentages of hexagonal cells in the corneal endothelium at baseline were 59.8 ± 10.8 compared with 61.9 ± 11.3 after dosing. Finally, the mean corneal thickness at baseline was 560 ± 36 µm compared with 568 ± 46 µm after dosing.

"There were no clinically significant negative changes in any measured safety parameter, including the endothelial cell density and morphology, the central corneal thickness, the visual acuity, slit-lamp biomicroscopy, IOP, or dilated funduscopy. The adverse events that were related to administration of levofloxacin were dysgeusia in 30% of the volunteers, ocular irritation in 7%, and ocular pruritus in 6%," Dr. Abelson commented.

Based on those findings, Dr. Abelson concluded that intensive dosing with levofloxacin 1.5% does not adversely affect the corneal endothelium.