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H Davidson, RR Dubielzig; An Experimental Model for Retinal Degeneration in the Cat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3485.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the toxic effect, both systemically and ocularly of a systemically administered antibiotic in normal cats Methods: As part of a safety study conducted on the FDA approved feline antibiotic enrofloxacin cats were intentionally given a toxic dose of the medication. Normal healthy adult cats, 16 female and 16 male, were included in the study. Cats received a complete physical examination including funduscopic examination prior to being placed on study. Cats were placed into 4 groups: control, 5mg/kg (standard medication dose), 20mg/kg, and 50mg/kg SID. Cats were dosed orally for 21 days. On days 0, 4, 11, 18, 25, and 32 ophthalmic examinations were completed. On d21 ½ the cats from each group were humanely killed. The remaining cats were observed for an additional 14 days and then humanely killed. Immediately after death the eyes were removed. Fixation of both globes was accomplished by front quarter perfusion with Karnovsky's fixative for both paraffin and plastic sections. The left eye was sectioned sagitally and processed in paraffin for light microscopy and the right segments of tapetal and nontapetal retina were sampled and embedded in resin for light and electron microscopy. Results: All cats in all groups remained systemically healthy throughout the study, with only ocular changes noted. Cats in the 20mg/kg and 50mg/kg groups had evidence of subtle changes visible on fundus examination, with the 50mg/kg group being more notable. On d18 of the study 2 out of 8 20mg/kg, and 6 out of 8 in the 50mg/kg group cats had funduscopic evidence of retinal degeneration. Histologically the retinas of all the high dose cats showed atrophy of photoreceptors and outer plexiform layers. The atrophy was seen throughout the retina but was more severe in the nontapetal retina. One of the 20mg/kg cats had atrophy of the outer plexiform layer but no abnormal features were detected by electron micrography. No abnormalities were found in the 5mg/kg group. Conclusion: A dose of 50mg/kg of enrofloxacin had a toxic effect on the feline retina. This toxic dose damaged the retina without an adverse effect on the cat's physical status.
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