Ear infection in cocker spaniel
Severe otitis externa in a four year old cocker spaniel. The ear canal is inflamed and swollen shut, and ceruminous exudate is present. Image by Joel Mills [GFDL, CC-BY-SA-3.0 or CC-BY-SA-2.5-2.0-1.0], via Wikimedia Commons.
As a general guideline, 5-10 drops (depending on the dog’s size) of topical antimicrobial agent should be applied to the ear twice daily, but in cases with ruptured tympanic membranes, all topically applied antibiotics are potentially ototoxic.

When the tympanic membrane is not intact or its patency is unknown, pet owners must be warned of potential adverse reactions. However, such cases are rare, and the benefits of topical antibiotics outweigh the risk of ototoxicity.

In acute Pseudomonas otitis cases, first-line topical antibiotics include neomycin, polymyxin and gentamicin.

Cases that fail to respond to initial therapy or cases of chronic Pseudomonas otitis call for second-line topical antibiotics such as tobramycin, amikacin, enrofloxacin, ticarcillin and silver sulfadiazine.

In these circumstances, presoaking the ear canal with Tris-EDTA enhances the activity of the subsequently applied topical antibiotic. Tris-EDTA disrupts the cell membranes of gram-negative bacteria, such as Pseudomonas species, allowing the antibiotics to permeate the bacteria and work more effectively.

View your activity >

Leave a Reply

Be the First to Comment!

Notify of


related content

Although “off-licence”, immunotherapy is well worth considering in our pruritic feline friends. Of course we … more

3 mins

Ever had one of those cases, which seem to typically occur around this time of year, that you think must be the start of an allergic dermatitis?

2 mins

David Cameron has praised a pioneering vet for “undoubtedly changing the fate of scores of vulnerable animals”.

6 mins

Have you ever had a puppy that just presents with lethargy, exercise intolerance and sleeps … more

2 mins

Many dogs will not pass faeces for the first 4 to 5 days after surgery.

1 mins

It is harder to correlate the grade of a heart murmur with the severity of the underlying heart problem in cats than it is in dogs. Some quite loud murmurs may occur with relatively small defects.

2 mins