Surolan is a prescription ear drop for dogs that treats otitis externa, the most common type of ear infection. It combines three active ingredients in a single suspension: an antifungal, an antibiotic, and a steroid. This triple-action formula targets the infection itself while reducing the inflammation, pain, and itching that come with it.
How Surolan Works
Each milliliter of Surolan contains three ingredients working in parallel. Miconazole nitrate (23 mg/mL) is a synthetic antifungal that kills yeast and also has some activity against certain bacteria. Polymyxin B sulfate (0.5293 mg/mL) is a broad-spectrum antibiotic effective against both gram-positive and gram-negative bacteria. Prednisolone acetate (5 mg/mL) is a corticosteroid that reduces swelling, redness, and itching inside the ear canal.
What makes the formula particularly effective is that the antifungal and antibiotic components work synergistically. In laboratory testing, the two antimicrobials together performed better than either one alone. The steroid component does not interfere with this antimicrobial activity to any meaningful degree, so all three ingredients pull their weight simultaneously.
What It Treats
Surolan is FDA-approved specifically for canine otitis externa caused by two organisms: the yeast Malassezia pachydermatis and the bacterium Staphylococcus pseudintermedius. These are the two most common culprits behind smelly, gunky, inflamed dog ears. Malassezia is a yeast that naturally lives on dog skin but can overgrow in the warm, moist environment of the ear canal, especially in floppy-eared breeds. Staphylococcus pseudintermedius is a bacterium that frequently colonizes dogs and becomes pathogenic when conditions are right.
Because ear infections in dogs often involve both yeast and bacteria at the same time, a combination product like Surolan can address mixed infections in a single treatment rather than requiring separate medications.
How It’s Applied
Surolan is a liquid suspension applied directly into the affected ear canal. Before your vet prescribes it, they will examine the ear to confirm the eardrum is intact. This step is essential because one of the ingredients, polymyxin B, can cause hearing damage if it reaches the middle or inner ear through a ruptured eardrum. Your vet will typically use an otoscope to visualize the tympanic membrane before starting treatment.
You’ll apply the drops at home, usually by tilting your dog’s head, squeezing the prescribed number of drops into the ear canal, and gently massaging the base of the ear to distribute the medication. Shake the bottle before each use since the suspension can separate. Between uses, store it below 25°C (77°F). Once you open the bottle, it stays stable for three months.
Safety and Side Effects
Most dogs tolerate Surolan well. The most important safety concern is using it only when the eardrum is confirmed intact. Applying it to an ear with a perforated tympanic membrane is contraindicated because the antibiotic component carries a risk of ototoxicity, meaning it can damage structures involved in hearing and balance.
Surolan should also not be used alongside other medications known to cause ototoxicity, as the combined risk increases. Based on post-market surveillance data compiled by the UK’s Veterinary Medicines Directorate, hearing impairment and deafness are reported very rarely, occurring in fewer than 1 in 10,000 treated animals. These cases appear mainly in elderly dogs, and the hearing loss is generally temporary once treatment stops.
Because Surolan contains a corticosteroid, prolonged use could theoretically lead to localized steroid effects like thinning of the ear canal skin. Your vet will typically set a defined treatment course rather than leaving it open-ended.
When Surolan Isn’t Appropriate
Beyond the perforated eardrum restriction, there are a few situations where Surolan may not be the right choice. If your dog’s ear infection is caused by organisms other than Malassezia or Staphylococcus pseudintermedius, the medication may not be effective. Your vet might swab the ear and send a sample for culture to confirm what’s growing before prescribing treatment.
Dogs with known hypersensitivity to any of the three active ingredients should not receive it. And because the product contains a steroid, your vet will weigh the risks carefully for dogs with conditions that corticosteroids can worsen, even when applied topically in small amounts.
Why Vets Choose Surolan Over Other Ear Drops
Several ear medications for dogs are available, and most work on similar principles: some combination of antifungal, antibacterial, and anti-inflammatory agents. Surolan’s particular advantage is its proven synergy between the antifungal and antibiotic components, which means it handles mixed yeast-bacteria infections efficiently. The formulation was evaluated through component effectiveness studies confirming that each ingredient contributes to the overall result without undermining the others.
For straightforward otitis externa caused by the common yeast and bacteria that plague dog ears, Surolan is a well-established option. More complicated or chronic infections, resistant organisms, or cases involving middle ear disease will likely require a different approach.