Amoxicillin for Dogs and Cats: Uses, Dosage, and Side Effects

Amoxicillin is a penicillin antibiotic that veterinarians commonly prescribe to treat bacterial infections in dogs and cats. It is FDA-approved for both species and is available in tablets and liquid formulations.

Here’s how amoxicillin works, when it’s prescribed, possible side effects, dosing guidance, and important safety information.

What Is Amoxicillin Used for in Dogs and Cats?

Amoxicillin is an FDA-approved penicillin antibiotic used to treat a variety of bacterial infections in dogs and cats.

FDA-approved uses: Amoxicillin is commonly prescribed to treat bacterial infections such as:

• Respiratory infections
• Urinary tract infections
• Abscesses, lacerations, and wounds

Extra-label uses: Veterinarians may also prescribe amoxicillin extra-label (off-label), meaning it is used in a way that is not included on the FDA-approved label.

Extra-label uses may include treating:

• Helicobacter infections
• Lyme disease

Available formulations: Amoxicillin is available as oral tablets and liquid formulations.

Compounded Amoxicillin 

In some cases, your veterinarian may recommend a compounded formulation of amoxicillin if an FDA-approved product is not the best option for your pet.

Compounded medications may be prescribed when:

• Your pet has difficulty taking the commercially available formulation.
• The required dosage strength is not commercially available.
• Your pet is allergic to an ingredient in the FDA-approved medication.

Compounded medications are not FDA-approved. They are prepared by a veterinarian or licensed pharmacist to meet an individual patient's specific needs.

Safety Considerations for Amoxicillin

Amoxicillin should not be given to dogs or cats that have previously had an allergic reaction to amoxicillin or other penicillin antibiotics.

Before starting amoxicillin, tell your veterinarian if your pet has a history of allergies to penicillin or amoxicillin so they can determine whether a different antibiotic would be a safer choice.

How Amoxicillin Works

Amoxicillin works by stopping bacteria from building the protective cell walls they need to survive.

Amoxicillin is classified as a penicillin antibiotic. As bacteria grow, amoxicillin prevents them from forming strong cell walls. This weakens the bacteria, causing them to die and helping your pet's body clear the infection.

How To Give Amoxicillin

Give amoxicillin exactly as directed by your veterinarian.

Administration tips:

• Follow the directions on the prescription label or those provided by your veterinarian.
• Amoxicillin may be given with or without food, although giving it with a meal may help reduce the risk of digestive upset.
• If using the oral suspension, carefully follow the mixing instructions and add the exact amount of water specified on the label.
• Shake the amoxicillin suspension well before giving each dose. 

What Happens If You Miss a Dose of Amoxicillin? 

If you miss a dose of amoxicillin, contact your veterinarian for guidance. In many cases, they may recommend giving the missed dose when you remember.

However, if it is almost time for your pet's next scheduled dose, they may advise skipping the missed dose and resuming the normal dosing schedule.

Do not give extra or double doses.

Amoxicillin Side Effects

Amoxicillin is generally well tolerated by dogs and cats, but gastrointestinal upset and allergic reactions can occur.

Common side effects include:

• Vomiting
• Diarrhea
• Loss of appetite
• Lethargy

Allergic reactions may include:

• Skin rashes (especially around the ears)
• Hives
• Facial swelling
• Vomiting
• Diarrhea
• Fever
• Anaphylaxis

Do not give amoxicillin to pets with a known allergy to penicillin or amoxicillin.

Human Side Effects

Humans should never take medication prescribed for pets, and pets should never receive medication prescribed for people because dosages often differ significantly.

If you accidentally ingest amoxicillin prescribed for a pet, seek medical attention or call Poison Control at 800-222-1222.

Monitoring Your Pet

No specific monitoring is required while your pet is taking amoxicillin. However, your veterinarian may recommend routine testing based on your pet's health, other medications, or the condition being treated.

When To Call Your Veterinarian

Contact your veterinarian if:

• Your pet develops severe side effects.
• Your pet's condition worsens or does not improve with treatment.
• You suspect your pet has received an overdose.
• You have additional questions or concerns about using amoxicillin.

Amoxicillin Overdose

An overdose of amoxicillin is unlikely to cause serious toxicity in dogs and cats, but it can still cause side effects and should be evaluated by a veterinarian.

Possible signs of an overdose include:

• Vomiting
• Diarrhea

If you suspect your pet has received an overdose, seek emergency veterinary care or contact an animal poison control center. Consultation fees may apply.

• Pet Poison Helpline: (855) 764-7661
• ASPCA Animal Poison Control: (888) 426-4435

How To Store Amoxicillin

Store amoxicillin according to the prescription label to help maintain its safety and effectiveness.

Storage instructions:

• Always follow the storage instructions on the prescription label.
• Store amoxicillin tablets and dry powder at temperatures at or below 77 F (25 C).
• After mixing, store the amoxicillin oral suspension in the refrigerator whenever possible and discard any unused suspension after 14 days.
• Keep the container tightly closed to protect the medication from moisture and light.
• Keep out of reach of children and pets.