CHAPTER 37 OTITIS EXTERNA, MEDIA, AND INTERNA 551
Maintenance Therapy Goals
Keep canals clear of debris with routine cleanings weekly to every other week; balance
overcleaning/overwetting with undercleaning.
Reduce bacterial and yeast colonization of the ear canal environment with cleansing
solutions or judicious use of topical medications.
Reduce inflammation and wax production with topical corticosteroids and treatment
of underlying causes of ear canal disease.
Examine ear canals at routine intervals to detect changes prior to the onset of clinical
symptoms.
COMMENTS
Do not use ivermectin in heartworm-positive dogs, or in collies, Shetland sheep-
dogs, Old English sheepdogs, Australian shepherds, and their cross-breeds; there is
increased risk of ivermectin toxicity in herding breeds; prevent ingestion of topical
ivermectins in herding dogs and their cross-breeds (due to possible ABCB1Δ[MDR1]
gene mutation).Ototoxicity has been reported with a large number of topical medications and ingredi-
ents; avoidance (if possible) is recommended if the tympanae are not intact (or cannot
be properly assessed); commonly reported ototoxic medications include aminogly-
coside and macrolide antibiotics, antineoplastic (platinum-based) agents, and loop
diuretics.Fig. 37.1.Normal tympanum in a 2-year-old male-castrate golden retriever. C, caudal; R, rostral; pf, pars
flaccida; pt, pars tensa; S, septum bulla (as visualized through intact tympanum); m, manubrium of the malleus;
h, tufts of hair on ventrum of canal proximal to tympanum.