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Effects of norfloxacin on the retina in rabbits
K Mochizuki1, T Higashide, M Torisaki
1Department of Ophthalmology, Kanazawa University School of Medicine, Japan.
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 micrograms norfloxacin, the oscillatory potential of the electroretinogram was transiently and selectively deteriorated in albino and pigmented rabbits, whereas the electroretinogram remained unchanged with 50 micrograms 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 micrograms norfloxacin. The electroretinogram and the retinal histology became abnormal 7 days after four intravitreal injections of 500 micrograms 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.
Conclusions:
These results indicate a high concentration of norfloxacin in the melanin-containing ocular tissues.
Insights
Intravitreal norfloxacin can affect retinal function, particularly in pigmented rabbits, due to its high concentration in melanin-rich ocular tissues. Further injections may lead to retinal abnormalities.
Area of Science:
- Ophthalmology
- Pharmacology
- Toxicology
Background:
- Fluoroquinolones exhibit melanin affinity, prompting reevaluation of ocular effects.
- Norfloxacin, a broad-spectrum fluoroquinolone, was investigated for ocular safety.
Purpose of the Study:
- To assess the retinal toxicity of intravitreal norfloxacin in rabbits.
- To determine the intraocular pharmacokinetics of intravitreal norfloxacin in rabbits.
Main Methods:
- Albino and pigmented rabbits were used to evaluate retinal toxicity and intraocular pharmacokinetics.
- Electroretinograms, visual evoked potentials, and retinal histology were analyzed.
Main Results:
- A 500 microgram dose of norfloxacin transiently affected the electroretinogram's oscillatory potential in both rabbit types.
- Retinal histology and electroretinograms showed abnormalities after multiple high-dose injections.
- Norfloxacin concentrations were high in the chorioretina and vitreous, persisting for days.
Conclusions:
- Norfloxacin accumulates to high concentrations in melanin-containing ocular tissues.
- Repeated intravitreal injections of norfloxacin can lead to retinal toxicity.