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Amoxicillin for Cats: Dosages, Side Effects and More

Stumped on the basics of amoxicillin for cats? Let’s look at why cats need it in the first place, the correct dosage, potential side effects and more.

Denise LeBeau  |  Sep 21st 2017


For many longtime cat guardians, amoxicillin for cats may not be a mystery. It is an antibiotic drug, in the penicillin family, used to prohibit the growth of bacteria. According to Tufts University and Medical News Today, it treats everything from bronchitis to Lyme disease to urinary tract infections in people. Amoxicillin for cats is used frequently on kitties with skin infections, urinary tract infections and ear infections.

When I asked my veterinarian, Shinnecock Animal Hospital’s Dr. Kelly Tierney (class of 2014), what she thought about the drug, she paused. “I learned the medications that became my ‘go-to’ drugs from my mentor. He always used an antibiotic in conjunction with clavulanic acid for ailments like urinary tract infections and gastrointestinal infections. So, I’d say newer vets are probably going with clavamox (an antibiotic with clavulanic acid) over amoxicillin, but it’s really your veterinarian’s call.” Depending on your vet’s preference, your cat may currently be on it. Here’s the scoop about amoxicillin for cats.

When do cats need amoxicillin?

A gray cat ready to take a pill from a human.

A gray cat ready to take a pill from a human. Photography by radleyhebdon/istock.

At one point, amoxicillin was the updated version of penicillin (patented by Bristol-Myers, 1975). It was considered better because it would be active longer, as per PetMD. It’s used in the treatment of cats with infections caused by bacteria, such as wounds (like animal bites), bladder infections, tooth abscesses, eye or ear infections, skin infections and respiratory infections. It can be used on GI infections, but it’s not effective against parasites (like tapeworms). Antibiotics are also usually recommended after surgical procedures, but Cummings Veterinary Medical Center at Tufts University indicates it’s prescribed on a per-case basis.

If your cat’s been in a fight, got a scrape, has itchy ears or runny eyes or he’s scratching like crazy, a trip to the vet will determine the best treatment. Some conditions, like urinary tract infections, are elusive. If your cat starts behaving oddly, especially by urinating outside his litter box, take him to the vet with a urine sample. Chances are he’ll be taking amoxicillin.

Best practices for amoxicillin dosage for cats

  1. Follow the timetable. One of the most important things about treating your cat with amoxicillin is to make sure you give the medication at the designated time and for the entire duration it’s prescribed — even if your cat’s symptoms are gone. If you stop the medication before the prescribed end-date, you are making your cat susceptible to an even worse ailment that might be impossible to treat. The World Health Organization states that antibiotic resistance is one of the biggest threats to global health!
  1. Never self-prescribe. Let’s say your cat seems to have an infection similar to the one he had last year and you have some amoxicillin from one of your illnesses in the house. Don’t give your cat amoxicillin prescribed for people – Vetinfo reports it could be toxic to your cat. Confirm every ailment’s origins before treating it. It could be a viral infection, in which case, amoxicillin is useless.
  1. Get a second opinion. If you feel that your cat is taking a lot of antibiotics, and not really improving, go to another veterinarian. Along with a possible misdiagnosis, amoxicillin and other antibiotics come with side effects. So being on them for a prolonged period of time without any improvement could be a red flag that something is wrong.

Potential side effects of amoxicillin for cats

Antibiotics, including amoxicillin, can cause a range of side effects for cats. Since every cat is an individual, each cat will respond differently to amoxicillin. PetCareRX mentions the following as the most prevalent side effects to antibiotics: rashes, fever, kidney or liver damage, diarrhea and vomiting.

Also, antibiotics can be particularly difficult on the digestive system, so confirm if your cat should take amoxicillin with or without food.

In addition, Vetinfo indicates that your cat could have dangerous complications if amoxicillin is taken while other antibiotics are in his system. And some cats are allergic to it. Monitor your cat closely while taking any medications, and alert your vet to anything out of the ordinary — health or behavior wise.

What about treating your cat with alternative medicine?

Take your cat to the veterinarian immediately any time he appears ill or injured. However, there are holistic approaches that can be effective in keeping your cat healthy in the first place, according to Dr. Shawn Messonnier, author of the Natural Health Bible for Dogs & Cats and Nutritional Supplements for the Veterinary Practice.

While we do not advocate using natural alternatives over traditional medications, learning more about supporting your cat’s immune system can help devise a lifelong healthy strategy. Amoxicillin treatment has many benefits, some side effects and should always be taken as directed by a professional vet. Communicating closely with your veterinarian is the best way to ensure your cat’s amoxicillin treatment is doing the trick to ensure his path to health and well-being.

Thumbnail: Photography by Shutterstock.

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