Amoxicillin and Clavulanic Acid for Dogs and Cats: Uses and Side Effects

By Dr Duncan Houston

Amoxicillin and clavulanic acid is a commonly prescribed antibiotic combination for dogs and cats. You may recognise brand names such as Clavamox or Synulox.

It can be useful for certain bacterial infections, but the diagnosis, formulation, and treatment plan matter. A swollen wound, itchy skin, or frequent trips to the litter tray does not automatically mean this is the right medicine.

Quick answer

Amoxicillin-clavulanic acid treats infections caused by susceptible bacteria, including certain skin, soft tissue, dental, and urinary infections. It does not treat viruses, and it is not a painkiller. Give the exact product and dose prescribed for your pet, follow the current treatment plan, and report side effects or poor improvement. Facial swelling, breathing difficulty, or collapse after a dose requires urgent veterinary attention.

What is amoxicillin-clavulanic acid?

The medicine combines two ingredients:

• Amoxicillin: a penicillin-type antibiotic that disrupts the cell walls of susceptible bacteria.

• Clavulanic acid: blocks certain bacterial enzymes, called beta-lactamases, that would otherwise break down amoxicillin.

Clavulanic acid helps amoxicillin work against some bacteria that resist amoxicillin alone. However, it does not overcome every form of antibiotic resistance.

It is also called amoxicillin-clavulanate or co-amoxiclav. Veterinary products include tablets, chewable tablets, and oral liquids, with different strengths and instructions.

What do vets use it for?

Problem	Where the medicine may help	What else matters
Infected wounds, bites, and abscesses	Susceptible bacterial infections in the skin and underlying tissues	Cleaning, drainage, or removal of damaged tissue may also be necessary.
Bacterial skin infections	Selected cases where a systemic antibiotic is appropriate	Many superficial infections can be managed with topical treatment.
Dental or periodontal infection	Selected infections alongside dental treatment	Antibiotics do not repair a diseased tooth or replace dental procedures.
Bacterial urinary infection	Cases where testing and clinical assessment support this choice	Urinary signs alone do not establish infection.
Certain bacterial respiratory infections	Selected cases based on the suspected organisms and illness	Many respiratory illnesses are viral or need a different antibiotic.

Approved indications vary by product and country. For example, US approvals include susceptible skin and soft tissue infections in both species, periodontal infections in dogs, and certain bacterial bladder infections in cats.

Being commonly prescribed does not make it suitable for every infection.

Why might my vet recommend something else?

For dogs with surface or superficial bacterial skin infections, current ISCAID guidance recommends topical antimicrobial treatment as the preferred initial approach when feasible. Oral antibiotics are not automatically required.

A cat with urinary discomfort may have feline idiopathic cystitis or stones rather than a bacterial infection. Even with a confirmed urinary infection, a narrower antibiotic such as amoxicillin alone may be appropriate.

Many uncomplicated respiratory illnesses and episodes of diarrhoea do not benefit from routine antibiotics. Dental disease also needs treatment of the affected teeth and tissues, rather than repeated antibiotic courses.

Your vet may choose this combination, another medicine, or no antibiotic after examining your pet and reviewing any test results.

What dose should my dog or cat receive?

The dose depends on the pet, infection, formulation, and relevant health conditions. Many oral prescriptions are given twice daily, but follow your own dispensing label.

Check:

• Your pet’s name and the medicine’s name.

• The tablet strength or liquid concentration.

• The number of tablets or millilitres per dose.

• How often to give it.

• The planned stop date or recheck date.

Different products may display the two ingredients separately or show their combined strength. Do not substitute a tablet or liquid based on a matching number alone.

If the instructions are unclear, ask the clinic or dispensing pharmacist to explain them before giving a dose.

How long should treatment last?

There is no single course length for every infection.

The aim is the shortest effective treatment supported by the diagnosis, response, and current guidance. Your vet may adjust the plan after reviewing culture results or reassessing your pet.

Give it for the duration currently prescribed. Do not stop because your pet looks better, continue until the bottle is empty, or restart leftovers without checking.

If your vet tells you to stop or change the antibiotic after a review, follow that updated instruction.

How do I give it safely?

Give oral doses with a small amount of food unless your vet directs otherwise. If hiding a tablet, use a small portion first so you can check that the full dose was swallowed.

For liquids:

1. Shake the bottle as instructed.

2. Measure with the supplied oral syringe.

3. Give it slowly and allow your pet to swallow.

4. Record the dose if several people share medication duties.

Do not use a kitchen spoon or mix the medicine into an entire meal your pet may not finish. If giving medication becomes a struggle or creates a bite risk, ask the clinic about another formulation or a safer technique.

What if I miss a dose?

Usually, give it when remembered unless the next dose is nearly due. In that case, skip the missed dose and resume the schedule. Do not give two doses together. Ask the clinic if you are unsure how to reset the timing.

What if my pet vomits after a dose?

Do not automatically repeat it. The amount already absorbed is uncertain.

Tell the clinic when the dose was given, when vomiting occurred, and whether you could see the tablet. They can advise what to do next.

What side effects should I watch for?

Digestive upset is among the recognised side effects. Vomiting, diarrhoea, reduced appetite, and drooling can occur. These signs can also reflect the underlying illness, so avoid assuming every change is caused by the medicine.

What you notice	What to do
A slightly softer stool, with normal appetite and behaviour	Monitor and contact the clinic if it persists or worsens.
Repeated vomiting, significant diarrhoea, refusal to eat, or unusual lethargy	Contact your vet promptly for advice before the next dose.
Hives or facial swelling	Stop giving the medicine and seek urgent veterinary advice.
Breathing difficulty, collapse, or rapidly worsening swelling	Go to an emergency veterinary clinic immediately.

When is this an emergency?

Suspected serious allergic reactions need immediate treatment. Do not give another dose while seeking help.

Bring the medication packaging and note the time of the last dose. If your pet may have swallowed extra tablets or chewed a bottle, contact your vet or an animal poison service immediately, even if they currently seem well.

Which pets need extra precautions?

Tell your vet about:

• Previous reactions to penicillins, cephalosporins, or this medicine.

• Kidney or liver disease.

• Pregnancy, nursing, or planned breeding.

• Other medicines, supplements, and recent antibiotics.

These details can change whether the medicine is appropriate or how it should be used. Pregnancy and nursing require an individual benefit-risk assessment.

Owners with a penicillin or cephalosporin allergy should tell the clinic and arrange advice about avoiding exposure during handling. Wash hands after giving medication.

How quickly should my pet improve?

The medicine starts acting before you can see a change. Improvement may become apparent over the next few days, depending on the infection and whether other necessary treatment has been provided.

Contact your vet if there is no clear improvement within about 48 to 72 hours, or sooner if that was the agreed review point. Worsening pain, spreading swelling, inability to eat or drink, or breathing problems should not wait for that window.

A poor response may mean:

• The bacteria are resistant.

• The illness is not bacterial.

• An abscess needs drainage.

• A foreign body or diseased tooth remains.

• Doses are being missed, spat out, or vomited.

The next step is reassessment, rather than simply choosing a “stronger” antibiotic. Culture and susceptibility testing can help guide treatment, particularly with recurrent or poorly responding infections.

How should I store it?

Follow the instructions for the exact product dispensed. Tablets and liquids may have different storage requirements.

As one example, reconstituted Clavamox Drops must be refrigerated and discarded after 10 days. That instruction should not be assumed to apply to every brand or compounded preparation.

Keep tablets protected from heat and moisture in their labelled packaging. Store all forms out of reach of children and animals, especially flavoured chewables.

Ask the clinic what to do if a liquid was left out, its appearance changed, or you cannot confirm when it was mixed. Do not add extra water to extend a bottle.

Common mistakes to avoid

• Giving leftover antibiotics for a new illness.

• Sharing medication between pets.

• Confusing liquid concentrations or tablet strengths.

• Repeating a dose after vomiting without advice.

• Stopping, extending, or restarting treatment independently.

• Ignoring the wound, tooth, allergy, or other underlying problem that allowed infection to develop.

Frequently asked questions

Is this stronger than ordinary amoxicillin?

It can work against some bacteria that produce enzymes which destroy amoxicillin. That makes it useful in selected circumstances, but not automatically better. Amoxicillin alone may be sufficient when the bacteria are susceptible.

Can I give my pet human amoxicillin-clavulanate?

Only if your vet has specifically prescribed that exact product and dose. Human products may have different strengths, ingredient ratios, or formulations. Do not use your own prescription or calculate a substitute from an internet chart.

Is it safe for cats?

It is an established veterinary treatment for appropriate bacterial infections in cats. Safe use depends on correct prescribing, administration, and monitoring. A cat’s treatment should not be copied from a dog’s prescription.

Does it relieve pain?

It has no direct pain-relieving action. Treating infection may improve comfort, but painful wounds, dental disease, and other conditions may need separate veterinary pain relief. Do not add human painkillers.

Successful treatment depends on matching the medicine to the infection, giving it accurately, and checking that your pet is improving. Keep the clinic informed when doses are difficult, side effects appear, or recovery is not following the expected plan.

If you are unsure why your dog or cat has been prescribed amoxicillin-clavulanic acid, ASK A VET™ can help you understand the questions to discuss with the prescribing veterinarian. Breathing difficulty, facial swelling, or collapse after medication requires urgent in-person care.