Ocular and systemic manifestations after oral administration of a high dose of enrofloxacin in cats.
OBJECTIVE
To characterize the effects of oral administration of a high dose of enrofloxacin to cats.


METHODS
24 (12 male and 12 female) young healthy cats.


METHODS
Cats were allocated on the basis of sex into 2 groups (4 males and 4 females/ group) from which 3 subgroups for 3 durations (3, 5, or 7 days) of enrofloxacin (50 mg/kg, PO, q 24 h) or control solution (1 mL of water, PO, q 24 h) administration that began on day -1 were created. Funduscopic examinations were performed daily. Electroretinography (ERG) was performed before and every 2 to 3 days after the start of oral administration. Four cats/study group were euthanized on days 3, 5, and 7, and eyes were collected for light and electron microscopic evaluations.


RESULTS
Neurologic, funduscopic, and ERG abnormalities were evident only in cats administered enrofloxacin. Funduscopic changes (granular appearance or graying of the area centralis) were noticed on or before day 3 (after only 3 days of enrofloxacin administration), with subsequent similar changes along the visual streak. Vascular attenuation (between days 2 and 4) and generalized tapetal hyperreflectivity (between days 5 and 7) followed. Reduction in b-wave ERG amplitude preceded funduscopic changes. Morphologic changes in the photoreceptor layers correlated with duration of enrofloxacin administration, with generalized degenerative changes evident after 3 doses.


CONCLUSIONS
The study indicated that a high dose of enrofloxacin (50 mg/kg/d, PO) induced retinal and systemic changes. Enrofloxacin at 10 times the recommended dosage is acutely toxic to the outer retina of clinically normal cats.
Ford
Marnie M
MM
Veterinary Medical Teaching Hospital, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA.
Dubielzig
Richard R
RR
Giuliano
Elizabeth A
EA
Moore
Cecil P
CP
Narfström
Kristina L
KL
D000284:Administration, Oral; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000009:adverse effects*; D001522:Behavior, Animal / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D002371:Cat Diseases / Q000139:chemically induced*; D002415:Cats; D000077422:Enrofloxacin; D005128:Eye Diseases / Q000139:chemically induced*; D005260:Female; D024841:Fluoroquinolones / Q000008:administration & dosage* / Q000009:adverse effects*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D012119:Respiration / Q000187:drug effects; D012160:Retina / Q000187:drug effects / Q000648:ultrastructure
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D000077422:Enrofloxacin