Skip to main content

Otomax (Canada)

This treatment applies to the following species:
Company: Merck Animal Health

Gentamicin sulfate, betamethasone valerate and clotrimazole ointment


Antibiotic, Anti-inflammatory, Antifungal

For Otic Use in Dogs Only

DIN 00817112


Gentamicin (as sulfate) is a water soluble (bactericidal) antibiotic of the aminoglycoside group, derived from Micromonospora, an actinomycete.

Betamethasone (as valerate) is a synthetic glucocorticoid derivative of prednisolone.

Clotrimazole is a synthetic antifungal belonging to the imidazole family.

Each gram of OTOMAX contains 3 mg gentamicin (as sulfate) USP, 1 mg betamethasone (as valerate) USP, and 10 mg clotrimazole USP in a mineral oil based vehicle containing a plasticized hydrocarbon gel.

Otomax Indications

OTOMAX is indicated for the treatment of canine acute and chronic otitis externa associated with yeast (Malassezia pachydermatis, formerly Pityrosporum canis) and/or bacteria susceptible to gentamicin.

Dosage and Administration

The external ear and ear canal should be properly cleaned and dried before treatment. Remove foreign material, debris, crusted exudates, etc., with suitable non-irritating solutions. Excessive hair should be removed from the treatment area of the external ear. Shake well before use when using the 15 g, 30 g and 215 g bottles. Instill OTOMAX into the cleaned external ear canal twice daily for 7 days.

- Dogs weighing less than 15 kg: 4 drops for the 7.5 g, 15 g and 30 g package sizes; or 2 drops, for the 215 g package size, per affected ear.

- Dogs weighing 15 kg or more: 8 drops for the 7.5 g, 15 g and 30 g package sizes; or 4 drops, for the 215 g package size, per affected ear.

Massage the external ear carefully after medication is instilled to assure proper distribution. Do not exceed the recommended period of treatment or frequency of application.


If hypersensitivity to any of the components occurs, treatment should be discontinued and appropriate alternate therapy instituted. Concomitant use of drugs known to induce ototoxicity should be avoided. Do not use in dogs with known perforation of eardrums.

CAUTIONS: Prior to treatment, it is recommended to conduct a clinical evaluation for evidence of hearing deficit and/or vestibular disorder. Antibiotic susceptibility of the pathogenic organism(s) should be determined prior to use of this preparation. Use of topical antibiotic and antifungals may permit overgrowth of non-susceptible bacterial, fungi or yeast. If this occurs, treatment should be instituted with other appropriate agents as indicated. Experimentally, it has been demonstrated that corticosteroids, especially at high levels, may result in delayed wound healing.

Adverse systemic reactions have been observed following the oral ingestion of some topical corticosteroid preparations. Patients should be closely observed for the usual signs of adrenocorticoid overdosage which include sodium retention, potassium loss, fluid retention, weight gain, polydipsia and/or polyuria. Prolonged use or overdosage may produce adverse immunosuppressive effects.


Keep out of the reach of children. Wash hands carefully after applying the product. In case of accidental contact with the eyes, rinse with copious amounts of water. Do not handle the product if you have known hypersensitivity against compounds in the product.

Adverse Reactions

While aminoglycosides are absorbed poorly from skin, intoxication may occur when aminoglycosides are applied topically for prolonged periods of time to large wounds, burns, or any denuded skin, particularly if there is renal insufficiency. All aminoglycosides have the potential to produce reversible and irreversible vestibular, cochlear, and renal toxicity. Following the use of parenteral, high-dose and/or prolonged or systemic synthetic corticosteroids, such as betamethasone, in dogs, ALP (SAP) and ALT (SGPT) enzyme elevations, weight loss, anorexia, polydipsia, polyuria, neutrophilia and lymphopenia have occurred. Cushing’s syndrome in dogs has been reported in association with prolonged or repeated steroid therapy. The following have been reported occasionally in humans in connection with the use of clotrimazole: erythema, stinging, blistering, peeling, edema, pruritus, urticaria, and general irritation of the skin not present before therapy. The use of these components has been associated with deafness or partial hearing loss in some dogs (e.g., geriatric). On rare occasions, especially in older dogs, permanent hearing losses or deficits were reported. If hearing loss, vestibular dysfunction (head tilt, circling, rolling, rhythmic movement of the eyes), hypersensitivity (pinnal irritation and erythema, application site pain and ulcers) or other reactions are noted during the course of treatment, discontinue use of OTOMAX immediately and flush the ear canal thoroughly with a non-ototoxic solution.

Information for Pet Owners: Consult your veterinarian in case of adverse reactions to this product. In most cases, the adverse reactions are transient and disappear after termination of treatment but in rare instances may be serious especially if treatment is not discontinued. The use of this drug product has been associated with deafness or partial hearing loss in some dogs (e.g. geriatric). On rare occasions, especially in older dogs, permanent hearing losses or deficits have been reported. If hearing loss, vestibular dysfunction (head tilt, circling, rolling, rhythmic movement of the eyes), hypersensitivity (redness and pain) or other reactions are observed, it is important to discontinue the use of OTOMAX immediately and contact your veterinarian. Do not exceed the recommended period of treatment or frequency of application.


Gentamicin: Gentamicin sulfate, a broad spectrum aminoglycoside antibiotic, is a highly effective treatment for bacterial infections of the ear and skin. In vitro tests have determined that gentamicin is bactericidal and acts by inhibiting normal protein synthesis in susceptible microorganisms. Specifically, gentamicin is active against the following organisms commonly isolated from canine ears and skin: Staphylococcus aureus, other Staphylococcus spp., Pseudomonas aeruginosa, Proteus spp., Escherichia coli, Alcaligenes spp., and Klebsiella spp.

Betamethasone: Betamethasone valerate is a synthetic adrenocorticoid for dermatologic use. Betamethasone, an analog of prednisolone, has a high degree of corticosteroid activity and a slight degree of mineralocorticosteroid activity. Betamethasone valerate, the 17-valerate ester of betamethasone, has been shown to provide anti-inflammatory and anti-pruritic activity in the topical management of corticosteroid-responsive otitis externa. Topical corticosteroids can be absorbed from normal, intact skin. Inflammation can increase percutaneous absorption. Once absorbed through the skin, topical corticosteroids are handled through pharmacokinetic pathways similar to systemically administered corticosteroids.

Clotrimazole: Clotrimazole is a broad-spectrum antifungal agent that is used for the treatment of dermal infections caused by various species of pathogenic dermatophytes and yeasts. The primary action of clotrimazole is against dividing and growing organisms. In vitro, clotrimazole exhibits fungistatic and fungicidal activity against isolates of Trichophyton rubrum, Trichophyton mentagrophytes, Epidermophyton floccosum, Microsporum canis, Candida spp., and Malassezia pachydermatis (Pityrosporum canis). Resistance to clotrimazole is very rare among the fungi that cause superficial mycoses. In an induced otitis externa infected with Malassezia pachydermatis, 1% clotrimazole in the OTOMAX vehicle was effective both microbiologically and clinically in terms of reduction of exudate odor and swelling. In studies of the mechanism of action, the minimum fungicidal concentration of clotrimazole caused leakage of intracellular phosphorus compounds into the ambient medium with concomitant breakdown of cellular nucleic acids and accelerated potassium efflux. These events began rapidly and extensively after addition of the drug. Clotrimazole is very poorly absorbed following dermal application.

Gentamicin-Betamethasone-Clotrimazole: By virtue of its three active ingredients, OTOMAX has antibacterial, anti-inflammatory, and antifungal activity. In component efficacy studies, the compatibility and additive effect of each of the components were demonstrated. In clinical field trials, OTOMAX was effective in the treatment of otitis externa associated with bacteria and Malassezia pachydermatis. OTOMAX reduced discomfort, redness, swelling, exudate, and odor, and exerted a strong antimicrobial effect.

TOXICOLOGY: Clinical and safety studies with OTOMAX have shown a wide safety margin at the recommended dose level in dogs (see CAUTIONS).


Store between 2° and 30°C.

How Supplied

OTOMAX is available in 15 g, 30 g and 215 g plastic bottles, as well as 7.5 g and 15 g tubes.

Intervet Canada Corp., subsidiary of Merck & Co., Inc., 16750, route Transcanadienne, Kirkland, QC H9H 4M7

To report an Adverse Reaction: 1 866 683-7838

® Intervet Canada Corp.

Version September 4th, 2018

CPN: 1208072.6

Intervet Canada Corp.

Order Desk:   514-428-7013
Toll-Free:   866-683-7838
Fax:   Toll-free 888-498-4444; local 514-428-7014
THIS SERVICE AND DATA ARE PROVIDED "AS IS". Animalytix assumes no liability, and each user assumes full risk, responsibility, and liability, related to its use of the Animalytix service and data. See the Terms of Use for further details.


Copyright © 2024 Animalytix LLC. Updated: 2024-02-27