The therapeutic plan for otitis externa requires identification of the primary disease process and perpetuating factors. Ideally management is aimed at thoroughly cleaning and drying the ear canal, removing or managing the primary factors, controlling perpetuating factors, administering appropriate topical or systemic therapy (or both), and evaluating response to therapy.
Ear cleaning serves several functions: (1) it removes material that supports or perpetuates infection; (2) it removes bacterial toxins, white blood cells (WBCs), and free fatty acids that stimulate inflammation; (3) it allows complete evaluation of the external ear canal and tympanum; (4) it allows topical therapy to contact all portions of the ear canal; and (5) it removes material that may inactivate topical medications. Significandy painful ears may benefit from initial anti-inflammatory therapy to decrease pain and swelling of the ear canal prior to cleaning. Severe cases of otitis externa often require general anesthesia to facilitate complete cleaning and evaluation of the external and middle ear.
Many different solutions are available for removing cerumen, exudate, and debris from the ear canal (Table Otic Cleaning Solutions). If the tympanic membrane cannot be visualized, only physiologic saline solution or water should be used, because many topical cleaning agents are ototoxic or incite inflammation of the middle ear. An operating otoscope, ear loops, and alligator forceps facilitate manual removal of large amounts of cerumen or debris. Debris is carefully removed under direct visualization, and care is taken deeper in the ear canal (close to the tympanic membrane). Aggressive hair removal is not advised, because inflammation and damage to the epithelium can result in secondary bacterial colonization and infection. Flushing may be performed after large accumulations of cerumen and debris are mechanically removed from the ear canal.
Otic Cleaning Solutions
|Trade Name||Acetic Acid||Boric Acid||Salicylic Acid||Isopropyl Alcohol||Propylene Clycol||Dss||Other|
|Ace-Otic Cleanser||2%||0.1%||Lactic acid 2.7%|
|Adams Pan-Otic||X||X||Parachlorometaxylenol, tris EDTA, methylparaben, diazolidinyl urea, popylparaben, octoxynol|
|Alocetic Ear Rinse||X||X||Nonoxynol-12, methylparaben, alovera gel|
|Cerulytic Ear Ceruminolytic||X||Benzyl alcohol, butylated hydroxytoluene|
|Cerumene||25% Isopropyl myristate|
|DermaPet Ear/Skin Cleanser for Pets||X||X|
|Earmed Boracetic Flush||X||X||Aloe|
|Earmed Cleansing Solution & Wash||X||50A 40B alcohol, cocamidopropyl phosphatidyl and PE dimonium chloride|
|Earoxide Ear Cleanser||Carbamide peroxide 6.5%|
|Epi-Otic Ear Cleanser||X||X||X||Lactic acid, chitosanide|
|Fresh-Ear||X||X||X||X||X||Lidocaine hydrochloride, glycerin, sodium docusate, lanolin oil|
|OtiCalm||X||Benzoic acid, malic acid, oil of eucalyptus|
|Otic Clear||X||X||X||X||X||Glycerin, lidocaine hydrochloride|
|Oticlean-A Ear Cleaning Lotion||X||X||X||35%||X||Lanolin oil, glycerin|
|Oti-Clens||X||X||Malic acid, benzoic acid|
|Otipan Cleansing Solution||X||Hydroxypropyl cellulose, octoxynol|
Flushing and evacuation of solution is done under direct visualization through an operating otoscope. A bulb syringe and red rubber catheter system may be used to both flush and evacuate solutions and accumulations from the ear canal. The operator, avoiding drastic pressure changes within the external ear canal that could damage the tympanum, should carefully control suction and manual evacuation of the contents of the bulb syringe from the ear canal. Other alternatives include tomcat catheters (3.5 F) or flexible, intravenous catheters (14 gauge, Teflon); stiff, narrow catheters should be used cautiously and under direct visualization deep in the external ear canal. Other reservoir systems for delivery or evacuation of solutions include a 12 mL syringe or suction tubing attached to in-house vacuum systems. In-house vacuum systems should be used cautiously and under direct visualization. Care should be taken to avoid trauma to the tympanic membrane until its integrity can be assessed. Initial flushes should be done with physiologic saline solution or water until the integrity of the tympanic membrane is established.
Other solutions may aid in the removal of wax in the ear canal. Ceruminolytics are emulsifiers and surfactants that break down ceruminocellular aggregates by causing lysis of squamous cells. A ceruminolytic agent in an alkaline pH may more effectively lyse squamous cells via cell surface protein disruption. Oil-based products soften and loosen debris to aid in their removal but do not cause cell lysis. Water-based ceruminolytics are easier to remove and dry more quickly than oil-based solutions, which are occlusive if they remain in the ear canal. Water-based products include dioctyl sodium sulfosuccinate, calcium sulfosuccinate, and carbamate peroxide, which has a foaming action with the release of urea and oxygen. Oil-based products include squalene, triethanolamine polypeptide, hexamethyltetracosane, oleate condensate, propylene glycol, glycerin, and mineral oil. In a recent study only the combination of squalene and isopropyl myristate in a liquid petrolatum base had no adverse effects on hearing, the vestibular system, and histopathologic examination. Other agents tested contained glycerin, dioctyl sodium sulfosuccinate (2% or 6.5%), parachlorometaxylenol, carbamide peroxide (6%), propylene glycol, triethanolamine polypeptide oleate condensate (10%), and chlorobutanol (0.5%).
Alcohol-based drying agents added to ceruminolytics include boric acid, benzoic acid, and salicylic acid, which decrease the pH of the ear canal, cause keratolysis, and have a mild antimicrobial effect. Drying the ear canal is important to combat increased humidity, which potentiates infection.
If the tympanum is intact, the ear canal is filled with a ceruminolytic agent for at least 2 minutes and the pinna is cleaned at the same time. The solution is flushed twice with warm water, and the canal inspected. The procedure is repeated until cleaning is complete. Other solutions commonly advocated for ear flushing include dilute chlorhexidine solution (0.05%), dilute povidone-iodine, and acetic acid (2.5%). The first two agents are potentially ototoxic or induce inflammation and should not be used if the tympanum is ruptured. A combination of propylene glycol malic, benzoic, or salicylic acid; 2% acetic acid; or dilute povidone-iodine have been suggested for use in dogs with a ruptured tympanum.
Owners may clean the ears at home with mild preparations of ceruminolytics and drying agents if mild otitis is present without severe accumulation of cerumen or exudate. Aqueous solutions are usually recommended because they are less occlusive and easier to clean from the ear, dog, and home environment.
The ear should be filled with the solution, then massaged for 40 to 60 seconds. The pet should be allowed to shake its head to remove the majority of the solution, and the excess should be wiped from the ear canal and pinna with a tissue. Daily flushing is usually recommended, followed by every other day, weekly, then as needed, depending on the solution. Ear swabs are not recommended for home use, because cerumen and debris may be forced into the horizontal ear canal and impact against the tympanic membrane
Erythematous ceruminous otitis externa is diagnosed 2.7 times more often than acute suppurative otitis according to one report. Yeast ± cocci were identified in those cases, with cocci or rods identified in suppurative otitis. Topical therapy should be based on the cytologic examination to diminish the incidence of inappropriate treatment (Table Topical Medications Used in the Treatment of Ear Disease). Many preparations combine anti-inflammatories and antimicrobials in an attempt to decrease the inflammation and combat bacterial or yeast overgrowth. All topical medications should be considered supportive, and specific treatment should be aimed at controlling the primary disease process.
Topical Medications Used in the Treatment of Ear Disease
|Generic Name||Trade Name||Dose||Frequency||Description|
|Fluocinolone 0.01% DMSO 60%||Synotic||4-6 drops; total dose<17mL||q12h initially. q48-72h maintenance||Potent corticosteroid anti-inflammatory|
|2-12 drops, depending on ear size||q12h initially. q24-48h maintenance||Mild corticosteroid anti-inflammatory|
|Hydrocortisone 1.0%, lactic acid||Epiotic HC||5-10 drops||q12h for 5 days||Mild corticosteroid anti-inflammatory, drying agent|
|Hydrocortisone 0.5%, sulfur 2%. acetic acid 2.5%||Clear X Ear Treatment||2-12 drops, depending on ear size||q12-24h initially. q24-48h maintenance||Mild corticosteroid anti-inflammatory, astringent, germicidal|
|DSS 6.5%. urea (carbamide peroxide 6%)||Clear X Ear Cleansing Solution||1-2 mL per ear||Once per week to as necessary||Ceruminolytic, lubricating agent|
|Chlorhexidine 2%||Nolvasan||Dilute 1:40 in water||As necessary||Antibacterial & antifungal activity|
|Chlorhexidine 1.5%||Nolvasan||Dilute 2% in
|q12h||Antibacterial & antifungal activity|
|Povidone-iodine 10%||Betadine solution||Dilute 1:10-1:50 in water||As necessary||Antibacterial activity|
|Polyhydroxidine iodine 0.5%||Xenodyne||Dilute 1:1-1:5 in water||As necessary, q12h, once weekly||Antibacterial activity|
|Acetic acid 5%||White vinegar||Dilute 1:1-1:3 in water||As necessary; q12-24h for Pseudomonas||Antibacterial activity, lowers ear canal pH|
|Neomycin 0.25%, triamcinolone 0.1%, thiabendazole 4%||Tresaderm||2-12 drops depending on ear size||q12h up to 7 days||Antibacterial & antifungal activity, parasiticide (mites), moderate corticosteroid anti-inflammatory|
|Neomycin 0.25%, triamcinolone 0.1%, nystatin 100,000 U/mL||Panalog||2-12 drops depending on ear size||q12h to once weekly||Antibacterial & antifungal activity, moderate corticosteroid anti-inflammatory|
|Chloramphenicol 0.42%. prednisone 0.17%, tetracaine 2%, squalene||Liquachlor, Chlora-Otic||2-12 drops depending on ear size||q12h up to 7 days||Antibacterial activity, mild corticosteroid anti-inflammatory|
|Neomycin 1.75 & polymyxin B 5000 lU/mL, penicillin C procaine 10,000 lU/mL||Forte Topical||2-12 drops depending on ear size||q12h||Antibacterial activity|
|Centamicin 0.3%, betamethasone valerate 0.1%||Centocin Otic Solution, Betagen Otic Solution||2-12 drops depending on ear size||q12h for 7 to 14 days||Antibacterial activity, potent corticosteroid anti-inflammatory|
|Centamicin 0.3%, betamethasone 0.1%, clotrimazole 0.1%||Otomax, Obibiotic Ointment||2-12 drops depending on ear size||q12h for 7 days||Antibacterial & antifungal activity, potent corticosteroid anti-inflammatory|
|Centamicin 0.3%, betamethasone valerate 0.1%, acetic acid 2.5%||Centaved Otic Solution||2-12 drops, depending on ear size||q12h for 7 to 14 days||Antibacterial activity, potent corticosteroid anti-inflammatory|
|Polymixin B 10,000 lU/mL, hydrocortisone 0.5%||Otobiotic||2-12 drops, depending on ear size||q12h||Antibacterial activity, mild corticosteroid anti-inflammatory|
|Enrofloxacin 0.5%, silver sulfadiazine 1%||Baytril Otic||2-12 drops, depending on ear size||q12h for up to 14 days||Antibacterial activity|
|Carbaryl 0.5%, neomycin 0.5%, tetracaine||Mitox Liquid||2-12 drops, depending on ear size||Antibacterial activity, parasiticide (mites)|
|Pyrethrins 0.06%, piperonyl butoxide 0.6%||Ear Mite and Tick Control||5 drops||q12h||Parasiticide (mites)|
|Pyrethrins 0.05%, squalene 25%||Cerumite||2-12 drops, depending on ear size||q24h for 7 to 10 days||Parasiticide (mites), ceruminolytic|
|Isopropyl alcohol 90%, boric acid 2%||Panodry||Fill ear canal||As necessary||Drying agent|
|Acetic acid 2%, aluminum acetate||Otic Domeboro||Fill ear canal||q12-48h||Drying agent, antibacterial activity, lowers ear canal pH|
|Silver sulfadiazine||Silvadene||Dilute 1:1 with water, 1 g powder in 100 mL water||q12h for 14 days||Antibacterial & antifungal activity|
|2-12 drops, depending on ear size||q12h for 14 days||1 L distilled water, 1.2g Tris EDTA, 1 mL glacial acetic acid; antibacterial activity|
|Silver nitrate||Use sparingly||As necessary||Cauterization of
ulcerative otitis externa
|Miconazole 1%; ± topical glucocorticoid (7.5 mL of dexamethasone phosphate (4 mg/mL] to10mLof1% miconazole)||Conofite||2-12 drops, depending on ear size||q12-24h||Antifungal activity|
|Ivermectin 0.01%||Acarexx||0.5 mL per ear||Once||Parasiticide (mites)|
|Pyrethrins 0.15%, piperonyl butoxide 1.5%||Many||2-12 drops, depending on ear size||Twice at 7-day interval||Parasiticide (mites)|
|Pyrethrins 0.05%, piperonyl butoxide 0.5%, squalene 25%||Cerumite||2-12 drops, depending on ear size||q24h for 7 days||Parasiticide (mites), ceruminolytic|
|Pyrethrins 0.04%, piperonyl butoxide 0.49%, DSS 1.952%, benzocaine 1.952%||Aurimite||10 drops||q12h|
|Rotenone 0.12%, cube resins 0.16%||Many||2-12 drops, depending on ear size||Every other day||Parasiticide (mites)|
Topical glucocorticoids benefit most cases of otitis externa by decreasing pruritus, exudation, swelling, and proliferative changes of the ear canal. The most potent glucocorticoids available in topical preparations are betamethasone valerate and fluocinolone acetonide. Less potent corticosteroids include triamcinolone acetonide and dexamethasone; the least potent is hydrocortisone. Most dogs benefit from short-term therapy with topical corticosteroids at the initiation of therapy, with concurrent therapy aimed at the primary and other perpetuating factors. Long-term therapy with topical corticosteroids can be deleterious because of systemic absorption of drug. Increased serum liver enzymes and depressed adrenal responsiveness may occur; with prolonged use iatrogenic hyperadreno-corticism is possible. Glucocorticoids alone may be of benefit for short-term therapy in cases of allergic or erythematous ceruminous otitis.
Antimicrobials are important for controlling secondary bacterial or yeast overgrowth or infection. Antimicrobials are indicated in any case with cytologic evidence of bacterial overgrowth or infection, with attention paid to the morphology and gram-staining characteristics of the bacteria. Otic preparations commonly contain aminoglycoside antibiotics. Neomycin is effective against typical otitis bacteria such as Staphylococcus intermedium. Gentamicin and polymyxin B are also appropriate initial topical treatments for gram-negative bacterial otitis externa.The significant risk of bone marrow toxicity in people limits the use of chloramphenicol for treating otitis in dogs and cats despite its antibacterial spectrum and availability.
Due to the frequency of resistant gram-negative bacteria such as Pseudomonas, other topical preparations have been developed. Enrofloxacin, ophthalmic tobramycin, and topical application of injectable ticarcillin have been used to treat otitis in dogs.< Their use should be limited to cases of resistant bacteria, and culture and susceptibility testing should be performed prior to application. Other topical agents may be used to supplement treatment of resistant Pseudomonas, such as silver sulfadiazine solution and tris EDTA. Tris EDTA can render Pseudomonas susceptible to enrofloxacin or cephalosporins by enhancing membrane permeability and altering ribosome stability. Frequent ear cleaning may also assist in the treatment of resistant bacterial otitis; ceruminolytics have antimicrobial properties, and their use in clinical cases has been evaluated. Acetic acid in combination with boric acid is effective against both Pseudomonas and Staphylococcus, depending on concentration and duration of exposure. Ear cleaning removes proinflammatory products, cells, and substances that diminish the effectiveness of topical antibiotics.
Many topical preparations control yeast organisms, which may complicate erythematous ceruminous otitis and suppurative otitis. Common active ingredients include miconazole, clotrimazole, nystatin, and thiabendazole. Preparations containing climbazole, econazole, and ketoconazole have also been evaluated. Eighty percent of yeast were susceptible to miconazole and econazole, intermediately resistant to ketoconazole, and 90% were resistant to nystatin and amphotericin B in one in vitro study. Topical ear cleaning agents have some efficacy against Malassezia organisms. Other preparations (e.g. chlorhexidine, povidone-iodine, acetic acid) are also effective in the treatment of secondary yeast overgrowth.
Response to topical therapy should be gauged by re-evaluation of physical, cytologic, and otoscopic examinations every 10 to 14 days after the initiation of therapy. Any changes in the results of these examinations should be recorded. Most cases of otitis can be managed topically; failure to respond to therapy should prompt re-evaluation of the diagnosis and treatment.
Systemic glucocorticoid administration may be beneficial in cases of severe, acute inflammation of the ear canal, chronic proliferative changes of the ear canal, and allergic otitis. Anti-inflammatory doses should be limited to 7 to 10 days. Cases of significant thickening or proliferative changes in the external ear canal benefit from systemic antimicrobial therapy. Systemic therapy should be considered if concurrent dermatologic changes of the surrounding skin, pinna, or other regions of the body are present. Long-term administration of appropriate antimicrobials based on culture and susceptibility is required in all cases of otitis media. Systemic therapy for yeast is rarely recommended in animals with otitis alone. One study evaluated oral itraconazole therapy, and in ear samples evaluated on cytology and culture, no change in cytology score was found.