The Side Effects of Amoxicillin in Cats

Amoxicillin can cause stomach upsets, so let Kitty have plenty of rest.
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If you have taken Kitty to the vet because she is ill or has a wound, you may have come back with a treatment of amoxicillin to give her. Knowing what the possible side effects are will help you decide if you need to contact the vet again.


Amoxicillin is a broad spectrum antibiotic, which is widely used for cats and dogs as well as humans. It is used to treat respiratory illnesses and a variety of infections, including tooth abscesses, wounds, injuries, skin infections, ear infections and urinary or bladder infections. The vet will give you a prescription for a set number of days and you should continue to give Kitty the full dose even if she appears to have recovered.


Amoxicillin can interact with other drugs you may be using on your cat. Make sure your vet knows of any other medication you give to your kitty. Amoxicillin can react with neomycin sulphate, antacids, aminoglycosides and bacteriostatic drugs used to inhibit bacterial growth. It can also interact with the antibiotics chloramphenicol and tetracycline. Your veterinarian needs to know your cat's other medications so that there will be no adverse side effects.

Common Side Effects

The most common side effects for amoxicillin and other antibiotics are gastrointestinal upsets. Cats commonly develop diarrhea or loose stools due to changes in the bacterial populations in their gut. Talk to your vet about feeding your kitty a small amount of yogurt to help with this. Other side effects can include vomiting, abdominal pain and decreased appetite. Cats with respiratory problems may have decreased appetite, as they cannot smell their food, so try a “smelly” food like tuna to tempt them.

Severe Side Effects

Cats can be allergic to medications, including amoxicillin, and show allergic reactions like breathing difficulties, swelling of the tongue, lips or face, hives, rashes, seizures, fainting, unusual bleeding or bruising. If this happens to your kitty, get her to a vet as quickly as possible. Do not double dose if you miss a treatment, as overdoses can cause skin allergies, vomiting, diarrhea, palpitations, lack of coordination, fever or chills. Always contact your veterinarian if you suspect an emergency.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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