Clavamox is a prescription antibiotic for dogs and cats that treats bacterial infections of the skin, soft tissue, gums, and urinary tract. It combines two active ingredients: amoxicillin, which kills bacteria, and clavulanate potassium, which prevents bacteria from resisting the amoxicillin. The FDA has approved it specifically for veterinary use, and it’s one of the most commonly prescribed antibiotics in small-animal medicine.
FDA-Approved Uses in Dogs and Cats
Clavamox is approved to treat skin and soft tissue infections in both dogs and cats. That includes wounds, abscesses, and cellulitis (infection spreading under the skin). In dogs specifically, it also covers superficial and deep skin infections like pyoderma, which shows up as crusty, red, or pus-filled patches on the skin. Periodontal (gum) infections in dogs are another approved use.
For cats, Clavamox has an additional approved indication: urinary tract infections caused by E. coli, the most common bacterium behind feline cystitis. If your cat is straining to urinate, urinating outside the litter box, or producing bloody urine, and a vet confirms a bacterial infection, Clavamox is a standard first-line treatment.
How Clavamox Works
Amoxicillin, the primary ingredient, kills bacteria by disrupting their ability to build cell walls. As bacteria grow and divide, amoxicillin locks onto proteins inside the cell wall and blocks the production of structural components the wall needs. Without an intact wall, the bacterial cell bursts.
The problem is that many bacteria produce enzymes called beta-lactamases, which break down amoxicillin before it can do its job. That’s where clavulanate comes in. It binds permanently to those enzymes and destroys them, essentially disarming the bacteria’s defense system. This combination lets Clavamox work against bacteria that would normally shrug off amoxicillin alone, including resistant strains of Staph and E. coli.
Which Bacteria It Targets
Clavamox is effective against a range of both Gram-positive and Gram-negative bacteria. In FDA clinical studies, the organisms most commonly isolated from treated infections included Staphylococcus aureus (both penicillin-resistant and penicillin-sensitive strains), other Staphylococcus species, Streptococcus species, and E. coli. Less commonly, infections involved Proteus, Pasteurella, Klebsiella, Enterobacter, and Acinetobacter.
It does not reliably cover Pseudomonas, which appeared in clinical studies but is generally not considered susceptible. If your vet suspects a Pseudomonas infection, they’ll likely choose a different antibiotic.
Typical Dosing
For dogs, the standard dose is 6.25 mg per pound of body weight, given twice daily. For cats, the typical dose is 62.5 mg twice daily regardless of weight, since most adult cats fall within a similar size range. Clavamox comes in both tablet and liquid suspension forms. The liquid version is often easier for cats and small dogs.
Your vet will determine the exact dose and duration based on the type and severity of infection. Skin infections may require 10 to 14 days of treatment, while urinary tract infections might call for a shorter or longer course. Finishing the full prescription matters even if symptoms improve early, because stopping too soon can allow surviving bacteria to rebound and develop resistance.
Side Effects
The most common side effects are gastrointestinal: diarrhea, vomiting, and loss of appetite. These are usually mild and resolve on their own. Giving Clavamox with food can reduce stomach upset in many pets.
Allergic reactions are possible, particularly in animals with a known sensitivity to penicillin-type antibiotics. Signs of an allergic reaction include facial swelling, hives, difficulty breathing, or sudden collapse. These are rare but require immediate veterinary attention.
Animals That Should Not Take Clavamox
Clavamox should never be given to rabbits, hamsters, guinea pigs, or other rodents. In these species, the drug disrupts the balance of gut bacteria so severely that it can cause fatal diarrhea. This is not a dose-dependent risk. Even small amounts can be dangerous.
Any dog or cat with a known allergy to penicillin or penicillin-type drugs should also avoid Clavamox, since amoxicillin belongs to the same drug family.
Storing the Liquid Suspension
If your vet dispenses the liquid form, it must be refrigerated after mixing. Shake the bottle well before each dose. The reconstituted suspension stays stable for 10 days in the refrigerator, after which any remaining liquid should be discarded. If you notice the medication has been left out at room temperature for an extended period, check with your vet before continuing to use it.