Otitis externa sometimes complicated, frustrating - DVM
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Otitis externa sometimes complicated, frustrating


DVM360 MAGAZINE


Treatment of bacterial otitis externa Generally most cases are readily cleared with appropriate topical treatments and systemic antibiotics are not helpful. Neomycin, gentamycin, and enrofloxacin containing otic preparations are the most commonly available products for treatment. I generally recommend topical treatments with corticosteroids if inflammation is moderate and advise systemic corticosteroids if inflammation is severe. Most cases are cleared in two to three weeks and may require weekly or twice weekly ear washes/rinses to be used as prevention. Products that contain acetic acid, boric acid, chlorhexidine with ceruminolytics or surfactants are most helpful. Clearly, identifying the primary cause is important and can include food trials and intradermal skin testing. I have not found antihistamines to benefit the treatment of otitis externa.

Treatment of bacterial otitis media After cytology is performed I advise a culture if appropriate and tend to be very aggressive with therapy. The bacterial cultures may need to be repeated several times during therapy. Initially, I advise sedation if there is a fair amount of discharge in the ear canal, pain with otoscopic examination, or if I cannot visualize the tympanic membrane readily. Routine flushes can be used to irrigate the canal during sedation and include saline or non-alcohol and surfactant-containing otic preparations. I have not found an increase incident of ototoxicity with products that have a reputation for causing such damage instill into an ear canal with a ruptured ear drum. If severe pain and/or hyperplasia is present (particularly in the Cocker Spaniel) I routine prescribe anti-inflammatory dosages of prednisone. Recently, oral cyclosporine has proved beneficial in the treatment of severe and hyperplastic otitis externa. I select antibiotics based upon results of cytology and culture and sensitivity. Routinely, I use topical antibiotics as well as systemic antibiotics pending results of culture.

Typically, I select aminoglycosides or fluoroquinolones for topical therapy.

For systemic therapy, I prefer oral amoxicillin/Clavulanate and Sulfa-type antibiotics for non-pseudomonal infections and oral fluoroquinolones for pseudomonal infections. The dosage for enrofloxacin for pseudomonas is 20 mg/kg/day. Please find below some recipes for topical therapies that will aid in the treatment of resistant pseudomonal infections.
  • Spectinomycin: 2 vials of synotic, 2 mg triamcinolone, and 1 cc spectinomycin mixed in 2 oz bottle.
  • Enrofloxacin: 2.5 cc injectable enrofloxacin, 15 cc sterile saline, 15 cc dexamethasone (2 mg/ml) mixed in 1 oz. bottle.
  • Ticarcillin: reconstitute 6 gram vial in 12 cc sterile water, divide in 2 ml portions in syringe and freeze unused portions, stable for three months.
  • Thaw and mix 2 ml of the prepared solution into 40 ml of sterile saline. Divide into four 10 cc aliquots and use or freeze (stable for months) or refrigerate (stable for about one week).
  • Amikacin: 15 ml amikacin (50 mg/ml) and 15 cc sterile water, placed in 1 oz bottle.
  • Silver sulfadiazine: Add 1.5 ml cream to 13.5 ml distilled water, warm and mix well in * oz bottle.
  • Neomycin/gramicidin/polymyxin ophthalmic drops, already prepared.
  • Ciprofloxacin ophthalmic drops: already prepared.
  • Tobramycin ophthalmic drops: already prepared.

I expect most cases of severe pseudomonal otitis media to be treated for four to six weeks with topical antibiotics (eliminate the corticosteroid-containing topical preparations in three to four weeks), eight to 12 weeks with systemic antibiotics. Generally, orally administered corticosteroids are ceased in two to three weeks.

Malassezia otitis usually is not complicated to treat, however I have seen several cases of severe, chronic, somewhat refractory cases of yeast otitis in the dog. Cytology readily demonstrates the typical yeast organism but on occasion, few or rare Malassezia organisms are found. I believe these latter cases to be a variant of the routine yeast otitis cases and should be treated similarly.

I advise topical clotrimazole/betamethaone containing products or products that contain miconazole. Most of these otic preparations contain corticosteroids and are useful in treating the pruritus and pain.

In severe cases, I recommend oral corticosteroids as I do in cases of severe bacterial otitis. Systemicketaconazole can also be useful in severe or recurrent cases.

For maintenance, I prefer to search for the primary cause, reduce swimming, and prescribe acetic acid/boric acid ear washes as preventive treatment.


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