Enrofloxacin-associated retinal degeneration in cats

Objective The objective of this study was to evaluate the possible relation ship between the administration of parenteral enrofloxacin and the onset of acute retinal degeneration The animals studied included 17 cats that recei ved systemic enrofloxacin and in cats. developed retinal degeneration soon thereafter. Procedures In this retrospective clinical study, cats that received parente ral enrofloxacin and developed acute blindness were identified. Parameters recorded included breed, age, sex, enrofloxacin dosage (daily dose and numb er of days administered), medical condition for which the antibiotic had be en prescribed, ophthalmic signs, examination results, and the visual outcom e. Fundus photographs were obtained in seven cats, and electroretinography was performed in five cats. Histopathology was performed on two eyes from o ne cat (case 1) that received enrofloxacin 5 months previously and develope d retinal degeneration. Results All cats were the domestic shorthair breed; seven were females (one neutered) and ten were males (seven castrated). Ages ranged from 3 to 16 y ears old (mean +/- SD; 8.8 +/- 4.6 years). The medical disorders for which enrofloxacin was administered ranged from lymphoma and pancreatitis to otit is and dermatitis, and eight cats had urinary diseases. The daily and total dosage of enrofloxacin and number of days of administration were also high ly variable. Presenting clinical signs were most often mydriasis and acute blindness. All cats had diffuse retinal degeneration as evidenced by increa sed tapetal reflectivity and retinal vascular attenuation. Absence of recor dable electroretinographic responses suggested diffuse and extensive outer retinal disease. Vision returned in a few cats, but the retinal degeneratio n persisted or even progressed. Histopathology of two eyes revealed primari ly outer retinal degeneration, with diffuse loss of the outer nuclear and p hotoreceptor layers, and hypertrophy and proliferation of the retinal pigme nt epithelium. Conclusion Parenteral enrofloxacin is potentially retinotoxic in some cats, and may result in acute and diffuse retinal degeneration. Blindness often results, but some cats may regain vision. Practitioners should adhere close ly to the manufacturer's current enrofloxacin dosage recommendation (5 mg/k g q 24 h), and continue clinical observations for this drug toxicity in cat s.