Otitis externa and otitis media are common in rabbits, particularly in lop-eared breeds.1,2 In 1 study of > 2,500 clinically normal rabbits, 32% of adult and 4% of young adult animals had evidence of unilateral or bilateral suppurative otitis media.2 In addition, 34% and 17% of affected adult and young adult rabbits, respectively, had otitis externa.2 Topical medication is the mainstay of treatment for otitis externa in human and veterinary medicine; however, in patients with tympanic membrane rupture, a number of topical medications have been found to have ototoxic effects.3–11 Topical antimicrobial administration is commonly used for treatment of otitis externa and otitis media in patients with tympanic perforation.12 In studies13,14 of human patients with otitis, topical administration of antimicrobials resolved infections more rapidly and effectively than did antiseptic treatment or placebo treatment, and no clear benefit was seen when systemic antimicrobial administration was were used alone. Similar evidence for the use of topical preparations in patients with otitis externa and otitis media is present in the veterinary literature, although the weight of evidence suggests that systemic antimicrobial treatment is also necessary in cases of otitis media in which the tympanic membrane is intact or has healed after myringotomy and lavage.15,16
In practice, topical antibacterial or antifungal medications are frequently administered in combination, often in otic preparations that contain a corticosteroid. When combination products are applied to the middle ear, it is possible that the drugs or other in-gredients (eg, the drug carrier or preservatives) have the potential to be ototoxic.
The purpose of the study reported here was to determine whether an ESS preparation (approved for the treatment of otitis externa in dogs and used extralabelly in cats and exotic species) would have ototoxic effects in healthy rabbits with and without intact tympanic membranes. We hypothesized that ototoxic effects (auditory response deficits as measured by BAER testing and histologic changes) would be observed in patients with ruptured tympanic membranes that received this treatment.
Not funded by any external source. The authors have no financial conflicts of interest or disclaimers to report.
Brainstem auditory-evoked response
Enrofloxacin–silver sulfadiazine emulsion
Scanning electron microscopy
C23 location (Canada), Charles River Laboratories, Wilmington, Mass.
Karl Storz, Tuttingen, Germany.
Nicolet VikingQuest EMG/NCS/EP System, Natus Medical Inc, Pleasanton, Calif.
Cadwell Industries Inc, Kennewick, Wash.
Coviden, Mansfield, Mass.
Baytril Otic, Animal Health Division, Bayer Healthcare LLC, Shawnee Mission, Kan.
Tousimis, Rockville, Mary.
SPI Supplies, West Chester, Pa.
FEI Teneo SEM, FEI Co, Hillsboro, Ore.
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