Effects of norfloxacin on the retina in rabbits

Background: Fluoroquinolones have a strong affinity with melanin, and their ocular effects have been reevaluated. Norfloxacin, one of the fluoroquinolones, has broad-spectrum activity against aerobic gram-positive and gram-negative bacteria. We examined the retinal toxicity and intraocular pharmacokinetics of intravitreal norfloxacin in rabbits. Methods: Twenty-three albino and 23 pigmented rabbits were divided into three groups to evaluate retinal toxicity and two groups to investigate the intraocular pharmacokinetics. Each of these five groups was further divided into two subgroups (albino rabbits and pigmented rabbits). Results: With 500 Etg norfloxacin, the oscillatory potential of the electroretinogram was transiently and selectively deteriorated in albino and pigmented rabbits, whereas the electroretinogram remained unchanged with 50 g in pigmented rabbits. No changes were observed in the visual evoked potential or on histology of the retina 7 days after an intravitreal injection of 50 or 500 ltg norfloxacin. The electroretinogram and the retinal histology became abnormal 7 days after four intravitreal injections of 500 g norfloxacin at 7-day intervals. As regards the intraocular pharmacokinetics after an intravitreal injection, the norfloxacin concentration in the chorioretina was as high as that in the vitreous 3 h after injection and was much higher than that in the vitreous 7 days after injection. Similar results were obtained after multiple injections. Conclusion: These results indicate a high concentration of norfloxacin in the melanin-containing ocular tissues.