Posatex is a prescription ear drop medication for dogs that treats otitis externa, the most common type of ear infection. It’s a combination product containing three active ingredients: an antibiotic, an antifungal, and a steroid, which together target the bacteria, yeast, and inflammation that typically drive ear infections in dogs.
How Posatex Works
Ear infections in dogs rarely involve just one problem. Bacteria, yeast, and swelling usually show up together, feeding off each other in a cycle that makes the infection worse. Posatex addresses all three at once with its three components.
The antibiotic component is a fluoroquinolone that kills bacteria by disrupting their ability to copy DNA, which stops them from multiplying. It’s effective against several common culprits in dog ear infections, including staph bacteria, Pseudomonas (a stubborn bacterium known for causing persistent infections), and Enterococcus. The antifungal component works by blocking an enzyme that yeast cells need to build their outer membranes, effectively killing the yeast. It targets Malassezia pachydermatis, the yeast species most commonly found in infected dog ears. The steroid component is a corticosteroid that reduces the redness, swelling, and itching that make ear infections so uncomfortable.
This triple-action approach is what makes Posatex a go-to choice for many veterinarians. Rather than prescribing separate medications, a single product handles the full picture of what’s going on inside the ear canal.
Dosing and How to Apply It
Posatex is applied once daily directly into the affected ear canal. The dose depends on your dog’s weight:
- Dogs under 30 lbs: 4 drops per ear, once daily
- Dogs 30 lbs or more: 8 drops per ear, once daily
Shake the bottle well before each use, since the active ingredients are suspended in the liquid and can settle. After placing the drops in the ear canal, gently massaging the base of your dog’s ear for a few seconds helps distribute the medication deeper into the canal. Your dog will almost certainly shake their head afterward, which is normal. Try to prevent them from scratching at the treated ear immediately after application.
Your vet will tell you how many days to continue treatment. Finishing the full course matters even if your dog’s ears look better partway through, because stopping early can allow resistant bacteria or yeast to bounce back.
Side Effects to Watch For
Most dogs tolerate Posatex well, but some develop mild redness or irritation at the application site. In clinical trials, ear pain, swelling, or warmth occurred occasionally, particularly at higher-than-recommended doses.
The most serious potential side effect is hearing loss. In the clinical field study of 143 dogs, one dog with infections in both ears developed hearing loss during treatment. The medication was stopped and the dog’s hearing returned within about a week. If your dog stops responding to sounds, seems disoriented, or tilts their head persistently during treatment, stop using Posatex and contact your vet.
Because Posatex contains a steroid, prolonged use at high doses can suppress cortisol production. This is unlikely at standard doses and treatment durations, but it’s one reason the medication is only available by prescription and should be used exactly as directed.
When Posatex Should Not Be Used
Posatex should never be used if your dog has a perforated eardrum. Before prescribing it, your vet will examine the ear canal to confirm the eardrum is intact. If the medication reaches the middle ear through a torn eardrum, it can damage the structures responsible for hearing and balance.
It’s also not appropriate for pregnant dogs, dogs that may become pregnant, or breeding animals. If your dog falls into any of these categories, let your vet know before starting treatment.
What to Expect During Treatment
Most owners notice improvement within the first few days. The swelling and redness start to go down, and dogs typically scratch at their ears less and seem more comfortable. The discharge and odor that often accompany ear infections should gradually clear up over the course of treatment.
If your dog’s symptoms aren’t improving after several days, or if they seem to be getting worse, that’s worth a follow-up visit. Some ear infections involve bacteria that are resistant to certain antibiotics, and your vet may need to take a swab and culture it to figure out exactly what’s growing in there. Chronic or recurring ear infections can also signal an underlying issue like allergies or anatomical problems (floppy-eared breeds are especially prone), which may need separate management to keep infections from coming back.