Different studies were conducted by different investigators to assess the feline ocular side effects of licensed veterinary fluoroquinolones 25-31. The results of these studies indicate that some fluoroquinolones have variable affinity for retinal tissues in cats, and that fluoroquinolone-induced retinal degeneration is a dose- and concentration-dependent adverse reaction rather than an idiosyncratic reaction.
Orbifloxacin and marbofloxacin approved for use in cats and dogs have also been reported to cause retinal damage and/or blindness in cats 30. For Baytril®, a NOEL of 25 mg/kg body weight for 15 days and a NOEL of 15 mg/kg body weight for at least 24 days were found, which are conveniently far away from the recommended therapeutic dose of 5 mg/kg body weight in cats 29.
Pradofloxacin was specifically investigated for the effects on the feline retina at variable dosing schemes 31, 32. The evaluated parameters included i.e. body weight, haematology, clinical chemistry, ophthalmological examinations, examinations of retinal thickness and structure of retinal layers and electroretinography.
Veraflox® clearly demonstrated its ocular and retinal safety: ocular and retinal toxicity were absent in all pradofloxacin treated cats, and the safety margin was determined to be at least 10-fold the recommended oral dose of 5 mg/kg body weight once daily for three weeks.