Amoxicillin is one of the most commonly prescribed antibiotics for dogs, used to treat a range of bacterial infections including skin and soft tissue wounds, urinary tract infections, respiratory infections, and dental disease. It belongs to the penicillin family and works by destroying the cell walls of bacteria, killing them as they try to grow and multiply.
FDA-Approved Uses in Dogs
Amoxicillin tablets are specifically labeled for use in dogs and cats. The FDA has approved amoxicillin-clavulanate (the combination version sold as Clavamox) to treat skin and soft tissue bacterial infections in dogs, including wounds, abscesses, and cellulitis. It’s also approved for periodontal (gum) infections in dogs specifically.
In veterinary practice, amoxicillin is also widely used for infections beyond its formal label. Veterinarians commonly prescribe it for upper respiratory infections, urinary tract infections, and infections caused by Streptococcus and Clostridium bacteria. Because amoxicillin covers a fairly broad range of bacteria, it’s often a go-to choice when the exact type of bacteria hasn’t been identified yet.
Skin, Wound, and Soft Tissue Infections
Skin infections are one of the primary reasons dogs end up on amoxicillin. If your dog has a bite wound, a surgical incision showing signs of infection, an abscess, or an area of red, swollen skin (cellulitis), amoxicillin can clear the bacteria driving the problem. These infections are common after fights with other animals, after surgery, or when a dog repeatedly licks or scratches a spot on their skin.
One important caveat: many skin infections in dogs involve Staphylococcus bacteria, and plain amoxicillin often can’t kill Staph on its own. That’s where amoxicillin-clavulanate comes in. The added clavulanate ingredient blocks a defense mechanism that Staph bacteria use to resist the antibiotic. So if your vet prescribes the combination version rather than plain amoxicillin, it’s likely because they suspect Staph is involved.
Dental and Gum Infections
Periodontal disease is extremely common in dogs, and bacterial buildup below the gumline can cause pain, tooth loss, and infections that occasionally spread to the bloodstream. Amoxicillin-clavulanate is specifically approved for treating gum infections in dogs. Your vet may prescribe it before or after a dental cleaning, or to treat an active tooth root abscess. A typical course runs 5 to 7 days, though your vet may extend it depending on severity.
Urinary Tract Infections
UTIs are another frequent reason dogs are prescribed amoxicillin. The most common culprit is E. coli, the same bacterium responsible for most UTIs in humans. However, resistance is a growing concern here. A 10-year study at a veterinary teaching hospital in Italy found that roughly 62% of E. coli samples from dogs with UTIs were resistant to amoxicillin alone. That resistance rate held steady across the entire decade.
Amoxicillin-clavulanate performed significantly better, with resistance dropping from about 53% to 26% over the same period. This is why many vets now reach for the combination version when treating UTIs, or they may run a urine culture first to confirm which antibiotic will actually work. If your dog keeps getting UTIs that don’t respond to treatment, resistance to the prescribed antibiotic is a real possibility worth discussing.
Plain Amoxicillin vs. Amoxicillin-Clavulanate
You’ll sometimes see your vet prescribe plain amoxicillin and other times the combination product (Clavamox or its generic equivalents). The rule of thumb is straightforward: anything plain amoxicillin can do, the combination version can also do, plus it can handle Staphylococcus bacteria that plain amoxicillin cannot. The exception is methicillin-resistant Staph (MRSA/MRSP), which resists both versions.
Plain amoxicillin tends to be less expensive and is a reasonable choice when the infection involves bacteria known to be sensitive to it, like Streptococcus or Clostridium. For skin infections, bite wounds, or any situation where Staph is a likely player, the combination version is the stronger bet.
How It’s Given
The standard dose for dogs is 5 mg per pound of body weight, given twice a day. So a 50-pound dog would typically get 250 mg per dose. It comes in tablet form and as an oral suspension (liquid), which is easier for small dogs. You can give it with or without food, though giving it with a meal can reduce the chance of an upset stomach.
Most courses last 5 to 7 days, or at least 48 hours after all symptoms have cleared. Finishing the full course matters. Stopping early because your dog looks better gives surviving bacteria a chance to bounce back, potentially with increased resistance to the antibiotic.
Side Effects to Watch For
Most dogs tolerate amoxicillin well. The most common side effects are digestive: decreased appetite, vomiting, and diarrhea. These are usually mild and resolve on their own. Giving the medication with food can help.
Allergic reactions are uncommon in dogs but can be serious. Signs include skin rash, fever, facial swelling, and difficulty breathing. Uncoordinated walking is another reaction that warrants immediate attention. If you notice any of these, stop giving the medication and contact your vet right away. Dogs with a known allergy to any penicillin-type antibiotic should not take amoxicillin.
Why Your Vet May Choose a Different Antibiotic
Amoxicillin is a solid first-line option for many infections, but it isn’t always the right one. Rising resistance rates, especially among bacteria that cause urinary and skin infections, mean that culture and sensitivity testing is increasingly important. If your dog’s infection isn’t improving after a few days on amoxicillin, your vet may switch to a different antibiotic based on lab results showing which drugs the specific bacteria respond to. This targeted approach is becoming standard practice as antibiotic resistance continues to be a concern in veterinary medicine.