Abstract
Abstract: :
Purpose: The goal of this study is to characterize the effect of two 4th generation fluoroquinolones, Vigamox (Moxifloxacin 0.5%) and Zymar (Gatifloxacin 0.3%) on corneal epithelial barrier function. Methods: Rabbit corneas were set in custom corneal perfusion chambers and pefused with BSS Plus. The ex–vivo topical treatments with Vigamox, Zymar, moxifloxacin 0.5% or gatifloxacin 0.3% consisted of 5–min exposure. The in–vivo treatment consisted of 1–week treatment with either Vigamox or Zymar and corneas mounted in the chambers. Carboxyfluorescein (CF, paracellular marker) or Sodium Fluorescein (SF, transcellular marker) was applied for 5 min. The perfusate was collected for 2 hours and the amount of CF or SF was determined by luminescence spectrometry. The permeability to fluorescein was quantified with the slope of linear regression. The amount of fluoroquinolones in the perfusate was measured by reversed–phase HPLC. Results: The rate of CF permeation in Zymar–treated corneas was significantly, 4.2x higher than in the controls and 1.6x higher than in the Vigamox–treated corneas (3.4±0.6 vs. 0.8±0.4 vs. 2.1±0.6). The rate of SF permeation was significantly, 1.8x higher in Zymar–treated corneas when compared to Vigamox whereas no differences were noted between the latter and the controls (0.5±0.2 vs. 0.28±0.1 vs. 0.35±0.1). The in–vivo treatment with Vigamox did not cause significant differences when compared to the controls, while Zymar yielded higher values (0.65±0.2 vs. 0.53±0.2 vs. 1.0±0.7). The rate of CF permeation following the ex–vivo treatment with gatifloxacin 0.3% was 3.4x lower when compared to Zymar (0.7±0.3 vs. 3.4±0.6) whereas moxifloxacin 0.5% caused 1.8x lower CF permeation than Vigamox (1.2±0.4 vs. 2.1±0.6). HPLC analysis revealed that 5–min ex–vivo treatment with Vigamox delivered 8.4x more fluoroquinolone on the endothelial side of the cornea ("anterior chamber") than Zymar. Conclusions: These studies indicate Zymar considerably damages the transepithelial paracellular pathway (tight junctions) in addition to the impairment of the transcellular route (cell membrane). The effect of Zymar appears to be due to BAK, since gatifloxacin 0.3% alone caused no damage to the corneal epithelial permeability whereas both Vigamox and moxifloxacin 0.5% produced similar corneal permeabilities. Vigamox treatment generated substantially higher drug penetration through the cornea than Zymar. Therefore, Vigamox offers advantages of better ocular tissue safety as well as penetration compared to BAK–induced toxicity from Zymar.
Keywords: antibiotics/antifungals/antiparasitics • cornea: epithelium