Small Animal Dermatology, 3rd edition

CHAPTER 37 OTITIS EXTERNA, MEDIA, AND INTERNA 549

Intact tympanum:

Ceruminolytic: dioctyl sodium sulfosuccinate, squaline, carbamide perox-

ide, propylene glycol (mild cleanser); most often used for in-hospital clean-

ing; irritating if not removed from ear canal

Antiseptics: acetic acid or 0.2% chlorhexidine gluconate;

parachlorometaxylenol (PCMX); monosaccharide complex;

trisaminomethane ethylenediaminetetraacetic acid (tris-EDTA) has

antibacterial and synergistic properties with certain antibiotics

Astringents: isopropyl alcohol, boric acid, salicylic acid

Antiinfective/parasiticide agents: specific to identified organism(s).

 Ear flushing:
Antiinflammatory therapy may be necessary prior to flushing to reduce swelling
Sedation may be required in painful cases and to prevent further trauma to the

canal

Gentle solutions should be used initially

A bulb syringe or properly trimmed French red rubber catheter is used to flush

in solution and remove debris

A catheter can be introduced into the bullae to permit flushing of the middle ear;

intubation is recommended if heavy sedation or general anesthesia is adminis-

tered

Repeat cleansing at a tapering frequency during therapy

Primary secretory otitis media treated by complete flushing of the middle ear;

repeat flushing may be required.

Drugs of Choice

 Topical medication:
Antibiotic: based on cytologic evaluation, culture and sensitivity testing,

and/or empiric choice; common commercial formulations contain gentamicin,

neomycin, marbofloxacin, enrofloxacin, orbifloxacin, florfenicol, polymyxin B,

or silver sulfadiazine

Additional antibiotics used topically (based on culture/sensitivity testing):

amikacin, ticarcillin disodium/clavulanate potassium, and tobramycin

Antifungal: imidazoles – lotrimazole, ketoconazole, miconazole, posaconazole,

thiabendazole; also nystatin, terbinafine

Antiinflammatory: corticosteroids: dexamethasone, fluocinolone, betametha-

sone, triamcinolone, hydrocortisone, and mometasone; also dimethyl sulfoxide

(DMSO); adrenal suppression occurs with topically applied corticosteroids

Combination antibiotic/antifungal/corticosteroid combination products are

widely used

Formulated products with excipients to permit longer exposure times for infect-

ing organisms with antimicrobials and longer contact time of the canal epithe-

lium with corticosteroids are available; particularly effective in acute otitis when

compliance with daily instillation of products is challenging

Caution when patency of the tympanic membrane is not known