Clavamox is a veterinary antibiotic used to treat bacterial infections in cats, most commonly skin wounds, abscesses, and urinary tract infections. It combines two active ingredients: amoxicillin, a penicillin-type antibiotic that kills bacteria, and clavulanic acid, which prevents bacteria from defending themselves against the antibiotic.
How Clavamox Works
Many bacteria, particularly Staphylococcus species, produce enzymes that can destroy penicillin-type antibiotics before they ever get to work. Clavulanic acid solves this problem by binding to those bacterial enzymes and neutralizing them, leaving the amoxicillin free to attack the bacteria’s cell walls. This two-ingredient approach makes Clavamox effective against a wider range of bacteria than amoxicillin alone, including strains that would otherwise be resistant to standard penicillin antibiotics.
Infections It Treats
Clavamox is FDA-approved for two categories of feline infections. The first is skin and soft tissue infections: wounds, abscesses, and cellulitis or dermatitis caused by susceptible bacteria. Cat bite abscesses are one of the most common reasons veterinarians prescribe it, since these wounds frequently harbor bacteria that produce those antibiotic-destroying enzymes.
The second approved use is urinary tract infections, specifically bladder infections (cystitis) caused by E. coli. Veterinarians sometimes prescribe Clavamox off-label for other bacterial infections as well, but skin/soft tissue and urinary infections are its labeled indications for cats.
How It’s Given
For cats, Clavamox typically comes as an oral liquid suspension (Clavamox Drops) rather than tablets, making it easier to dose smaller animals. The standard recommended dose is 62.5 mg given twice daily, which works out to 1 mL of the liquid suspension per dose. Your veterinarian may adjust this based on your cat’s weight and the severity of the infection.
You can give Clavamox with or without food, but giving it with a meal helps reduce the chance of stomach upset. If your cat tends to be sensitive to medications, pairing the dose with a small amount of food is worth trying. Treatment courses typically run 5 to 7 days for uncomplicated infections, though your vet may prescribe a longer course for deeper wounds or stubborn infections. Finishing the full course matters, even if your cat seems better after a few days, because stopping early can allow surviving bacteria to bounce back.
Common Side Effects
The most frequent side effects are gastrointestinal: diarrhea, vomiting, and reduced appetite. These are generally mild and often improve when the medication is given with food. Most cats tolerate Clavamox without significant problems.
One side effect worth watching carefully in cats specifically is complete loss of appetite. Cats that stop eating entirely for more than a day or two can develop a serious liver condition called hepatic lipidosis, where fat accumulates in the liver. If your cat refuses all food while on Clavamox, that warrants a call to your veterinarian rather than a wait-and-see approach.
Rare but more serious reactions include fever, skin rashes, difficulty breathing, and pale gums. These signs suggest an allergic reaction and need immediate veterinary attention. Cats with a known allergy to any penicillin-type antibiotic should not take Clavamox.
Storing the Liquid Suspension
Clavamox Drops come as a powder that your veterinarian or pharmacist mixes with water before dispensing. Once reconstituted, the liquid needs to be refrigerated to stay effective. At room temperature, the suspension remains stable for only about five days before it starts losing potency. Refrigerated properly (between 36°F and 46°F), it lasts through a standard treatment course. If you accidentally leave it out on the counter overnight, it’s not immediately ruined, but consistently storing it at room temperature will compromise the medication. Keep it in the fridge, shake it before each dose, and discard any leftover suspension after your cat finishes the prescribed course.
Cats That Shouldn’t Take Clavamox
The main contraindication is a penicillin allergy. If your cat has ever had a reaction to amoxicillin, ampicillin, or any other penicillin-family drug, Clavamox is off the table. Because clavulanic acid protects the amoxicillin rather than acting as a separate antibiotic, the core medication is still a penicillin, and the same allergy risks apply. Let your vet know about any previous antibiotic reactions before starting treatment.