Retinal safety of a new fluoroquinolone, pradofloxacin, in cats: assessment with electroretinography

Purpose To investigate the safety of a new fluoroquinolone, pradofloxacin, on the cat retina using electroretinogram. Methods Ganzfeld ERGs were recorded in 40 cats treated orally for 23 days in 4 groups: CTRL (n = 9): placebo-vehicle; PRADO30 (n = 10): pradofloxacin 30 mg/kg/day; PRADO50 (n = 14): pradofloxacin 50 mg/kg/day; and ENRO30 (n = 7): enrofloxacin at toxic doses of 30 mg/kg/day. ERG was performed before treatment and once weekly during the treatment period. An extended ISCEV protocol with addition of 8 steps of increasing luminance in dark adapted condition was carried out to assess: V_max (saturated scotopic b-wave amplitude) and k (luminance inducing V_max/2). OCT and retinal histological changes were also investigated. Results Pradofloxacin showed no effects in respect to rod b-wave, V_max, k and maximum scotopic a-wave (P > 0.05). Oscillatory potentials, cone ERG and flicker were also unaltered (P > 0.05). Rod b-wave was undetectable after treatment in ENRO30 group, V_max was reduced to 10.5% of the baseline (P < 0.05), accompanied by an increase of k by 1 log cd s/m² (P < 0.05). Oscillatory potentials, cone b-wave amplitude and 30 Hz flicker amplitude were reduced to 8.3%, 58.9% and 37.4% of the baseline, respectively (P < 0.05). Effects were also seen in OCT and retinal histology starting within one week after the start of treatment and thereafter remaining stable. Conclusion Pradofloxacin at 6 and 10 times the recommended doses was shown to have no retinal toxic effects in cats, neither on rod or cone function with ERG.