Ear infections in pets are painful, itchy, stinky, greasy, puffy, raw and seem to come in every color of the rainbow. Just about everyone agrees that ear infections are disgusting, but hardly any two veterinarians treat ears the same way. Some practitioners go for a definitive diagnosis. Others treat with a broad-spectrum medication and watch for the response. One veterinarian swears by Animax ointment. Another reaches for Otomax or Tresaderm. Some consider cleansers a key component in ear treatment and care, while others take a conservative approach. Job OneTalking to vendors of ear-care products can be as overwhelming as trying to get veterinarians to agree on the best ones and how they should be used. Veterinary Practice News talked with two nationally known veterinary dermatologists on the subject, along with representatives from veterinary otic manufacturing companies, for a current sampling of remedies. Job One is to diagnose the underlying cause, said Paul Bloom, DVM, owner of the Allergy, Skin and Ear Clinic for Pets in Livonia, Mich. “If you ignore this, you are doomed to recurrence,” warned Bloom, a diplomate of both the American College of Veterinary Dermatologists and the American Board of Veterinary Practitioners, canine and feline specialty. Otitis can be just one symptom of an overall dermatologic condition. Second point: Use enough topical medicine to attack the problem. “The reason people have trouble clearing up these ears is, they’re not getting the medicine down in there,” said Dr. Bloom, an adjunct professor at Michigan State University College of Veterinary Medicine. Bloom’s rule of thumb for dispensing otic topicals is 1 mL per ear, per 50-pound dog. “When you use ‘five drops,’ you’re just asking for catastrophe,” he emphasized. “The medicine is not getting into the ear canal. “When I send home Otomax for a golden retriever in 15-gm tubes for 10 days of treatment, [the client is] going to get four to five tubes,” he continued. “Virbac’s new product, Easotic, is a good choice because it precisely dispenses 1 mL of product and is labeled for once daily use for five days.” How Much Is Enough? It’s a point well taken, says Jon Plant, DVM, owner of the SkinVet Clinic in Lake Oswego, Ore. A diplomate of the American College of Veterinary Dentistry, he has lectured on otitis at national meetings and is a former dermatology professor at Oregon State University’s College of Veterinary Medicine. “The proper quantity of otic medication to instill per ear is a matter of judgment, but the ear canals of large-breed dogs certainly warrant a significantly larger quantity than toy-breed dogs,” he said. “Measuring that quantity in terms of drops is usually challenging for pet owners, anyway.” The label for Otomax directs using four drops twice daily for dogs less than 30 pounds and eight drops for dogs weighing 30 pounds or more. Tresaderm calls for five to 15 drops per ear twice daily, depending on severity and extent of the lesions. Baytril Otic‘s label says to use five to 10 drops twice daily in dogs up to 35 pounds, and 10 to 15 drops in larger dogs. “Almost all ear medication for dogs is either a squeeze bottle where the owner has to count drops or an ointment, where you can’t see the amount going into the ear,” noted Heidi Lobprise, DVM, senior technical manager with Virbac Corp. of Fort Worth, Texas. “It’s even more challenging with a painful animal that is, meanwhile, jumping around during the entire process,” Heidi said. “The result can be a decline in successful treatment of the case, due to a decline in 100 percent client compliance.” I Hear That Experts concur that systemic antibiotics are inadequate to squash the bad-boy bugs of otitis externa. They also concur that some animals won’t hold still for clients to topically medicate their ears. For a quick review of otitis products, click here. Cristiano von Simson, DVM, technical services manager for Bayer Healthcare LLC Animal Health, stands by Baytril Otic’s label and has confidence in application by drops. “Hold the ear up with one hand and rest the hand on the head of the animal, and don’t put the tip all the way in,” he said. “Aim at the ear channel and really watch the drops.” The water-based Baytril Otic is thinner and more susceptible to gravity, Dr. von Simson said, so gently massaging the base of the ear carries the medication to the bottom of the ear canal. Virbac’s Dr. Lobprise highlighted Easotic’s innovative cannula system. “This unique dispensing system has a flexible cannula that works no matter how the bottle is held,” she said. “The airless pouch applicator delivers the precise 1 mL dose when held in any position.” Check and Recheck The third major point is to get patients back for rechecks, Bloom said. “Don’t dispense medication without seeing the dog. Intermittent Otomax or Baytril can allow pseudomonas to flourish,” he said. Finally, “Massaging the base of the ear is very important to get the medicine into the horizontal canal,” Bloom said. Are label directions on frequency and duration of use of prescription ear medications realistic? Plant said, “I generally use ear medications at the frequency suggested by the manufacturer, although often for a longer duration, depending upon the severity of the infection.” Aminoglycoside antibiotics, specifically gentamicin and neomycin, are commonly used in prescription ear medications, and Bloom considers this class his first-line otic drug. Flouroquinolone ear medications containing enrofloxacin or orbifloxacin should be reserved as the “third-line” choice for cases non-responsive to gentamicin, he said. Used routinely, flouroquinolones can lead to resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), Bloom said. “Even if the ear looks normal and appears to be cleared up, the staph bacteria can still be present and flouroquinolone antibiotics can turn on MRSA genes, allowing proliferation of MRSA,” he said. Ototoxicity Another issue is aminoglycoside drugs and ototoxicity. Bloom cited two studies that concluded gentamicin did not harm the middle ear, so he doesn’t fear using it in cases of suspected tympanic membrane rupture. “It is important to note that ototoxicity is from inner, not middle, ear damage,” Bloom said. “In otitis externa, the tympanic membrane is often thickened, so gentamicin-based medications rarely reach the middle ear.” Moreover, he said, the middle ear communicates with the inner ear through the round window and oval window, both of which are covered by a membrane. “In cases of otitis media, the membranes are usually thickened, preventing penetration of medication into the inner ear,” he said. Informed Consent When dispensing Otomax or a generic equivalent, “Be sure to inform owners of the possible, be it rare, occurrence of deafness associated with this product,” Bloom said. “It usually is transient, but it can be permanent. You might consider an in-clinic prepared handout for clients similar to those used when dispensing non-steroidal anti-inflammatory drugs,” he added. Otomax, arguably the most popular ear product in veterinary medicine, is manufactured by Merck Animal Health. Active ingredients are gentamicin sulfate USP, betamethasone valerate USP and clotrimazole USP. The warning label states: “The use of Otomax ointment has been associated with deafness or partial hearing loss in a small number of sensitive dogs (e.g., geriatric). The hearing deficit is usually temporary. If hearing or vestibular dysfunction is noted during the course of treatment, discontinue use of Otomax ointment immediately and flush the ear canal thoroughly with a non-ototoxic solution.” The same label warning is carried on Mometamax, another Merck ear medication whose active ingredients are gentamicin sulfate USP, mometasone furoate monohydrate and clotrimazole USP. The few deafness cases were idiopathic, Bloom said, meaning without apparent cause.
