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Amoxicillin for Cats: Uses, Doses & Side Effects (Vet Answer)

Vet approved

	Dr. Iulia Mihai Photo

Written by

Dr. Iulia Mihai

Veterinarian, DVM MSc

The information is current and up-to-date in accordance with the latest veterinarian research.

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Amoxicillin is an antibiotic that is prescribed to cats for various infections (from skin infections to gastrointestinal infections). It has a broad spectrum of action against a very large range of gram-positive and gram-negative bacteria, including Streptococcus and Staphylococcus.

This medicine is only available with a prescription. Amoxicillin should not be used in combination with certain drugs and should be avoided in cats that are allergic to it. Adverse effects of amoxicillin administration may include the following clinical signs: vomiting, diarrhea, itching, shortness of breath, and swelling of the face.

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What Is Amoxicillin?

Amoxicillin is a broad-spectrum, semi-synthetic penicillin that has bactericidal properties against a wide range of gram-positive and gram-negative bacteria, such as:

  • Staphylococcus aureus
  • Streptococcus spp.
  • coli
  • Proteus mirabilis
  • Pasteurella multocida

It is used in cats for various bacterial infections, such as respiratory, skin, gastrointestinal, or urinary tract infections. Amoxicillin is available under different brand names, such as:

  • Amoxil®
  • Amoxi-Tabs®
  • Amoxi-Drop®
  • Bimox®
  • Moxatag®
  • Novamoxin®
a bottle of Amoxicillin tablets spilling out
Image Credit: luchschenF, Shutterstock

How Is Amoxicillin Given?

Amoxicillin is available in the form of tablets, capsules, powder for oral suspension, or drops. Although it can be administered with or without food, it is recommended to give it to your pet after a meal because it can disturb the digestive tract, and vomiting may occur.

The medicine should be administered for the entire period recommended by the veterinarian. Do not stop the administration unless gastrointestinal disorders, lethargy, breathing with difficulty, or swelling of the face occur, and in these situations, you must contact the vet.

The liquid forms should be measured carefully and shaken well before administration. Once you start giving amoxicillin to your cat, you should see improvements within a few days. Depending on the product or vet’s recommendations, the usual dose of amoxicillin for cats is 5–10 mg/lb., once or twice a day.

In the case of skin abscesses, amoxicillin will be administered for 5–7 days or 2 days after all clinical signs have disappeared. In the case of urinary infections, treatment with amoxicillin lasts 10–14 days on average, but you should not administer it for more than 30 days.

What Happens If You Miss a Dose?

In case you missed a dose, do not give your cat two doses at once. Wait until the next scheduled dose if you are closer to that, or give your cat the medicine when you remember and then return to their usual dosing schedule. Giving your cat two doses at once isn’t likely to cause severe harm but may cause side effects.

Woman at home holding her lovely Devon Rex cat on lap and gives it a pill
Image Credit: Veera, Shutterstock

Potential Side Effects of Amoxicillin

Like any other drug, amoxicillin is not without potential side effects. These include:

In severe cases, amoxicillin can cause the following clinical signs:

  • Rash
  • Excessive scratching
  • Breathing difficulties
  • Fever
  • Swelling of the face
  • Wobbly walking (incoordination)
  • Prolonged lack of appetite

For cats with liver or kidney disease, the side effects of amoxicillin may last longer. However, for cats that do not suffer from chronic conditions, the side effects will usually resolve within 24 hours. If the side effects last more than 24 hours, contact the veterinarian.

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Frequently Asked Questions (FAQ)

Are There Any Risk Factors for Amoxicillin in Cats?

Amoxicillin should be used with caution in pregnant or lactating cats and in those with liver or kidney diseases. Also, this antibiotic should not be used in cats that are allergic to amoxicillin or other penicillins, beta-lactams, or cephalosporins. Even if the allergic reactions are not usually severe, there are cases in which if not intervened quickly, they can lead to difficulty breathing, swelling of the face, and even death.

Can I Give 500 mg of Human Amoxicillin to My Cat?

Even if the ingredients used are similar for humans and animals, veterinary amoxicillin is the safest choice for your cat. Amoxicillin for human use risks exposing your cat to toxic substances, such as certain chemical preservatives or flavors (like xylitol). Also, 500 mg of amoxicillin will be difficult (if not impossible) to dose for your cat’s weight. A proper dose of amoxicillin in cats is 5–10 mg/lb.

american shorthair cat checked by vet
Image Credit: 89stocker, Shutterstock

Does Amoxicillin Have Any Drug Interactions?

If your cat is taking methotrexate, warfarin, probenecid, bacteriostatic antimicrobials, vitamins, herbal medicines, or supplements, it is recommended to notify the veterinarian before starting a round of amoxicillin.

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Amoxicillin is an antibiotic with a broad spectrum of action that is prescribed for skin, gastrointestinal, respiratory, or urinary infections. The usual dose for cats is 5–10 mg/lb., once or twice per day. Amoxicillin can cause adverse reactions, the most common being vomiting, diarrhea, loss of appetite, and lethargy. In severe cases, it can lead to rash, itching, difficulty breathing, and/or swelling of the face. In such cases, if you do not intervene in time, your cat may die. Pregnant or lactating cats and those suffering from liver or kidney diseases should be given amoxicillin with caution.

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Featured Image Credit: Sonis Photography, Shutterstock