Amoxicillin Side Effects in Dogs

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Amoxicillin Side Effects in Dogs
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Ever-curious, your dog scrambles off the beaten path on a walk and cuts his paw on broken glass. Your vet may prescribe the antibiotic amoxicillin if his paw gets infected. Similarly, if you notice your dog scratching to go out incessantly, he may need amoxicillin for a urinary tract infection. Just as humans are prescribed amoxicillin for a variety of ills, your dog may be as well.


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Antibiotics for dogs

Amoxicillin is just one of many antibiotics vets prescribe for pets. Enrofloxacin (brand name Baytril) and metronidazole (Flagyl) are also commonly used for infections.

Amoxicillin, often combined with clavulanic acid to improve effectiveness and sold by the brand name Clavamox, is used to treat respiratory, ear, skin, urinary tract, and gastrointestinal bacterial infections, as well as Lyme disease, in dogs. It works by preventing the bacterial cell walls from forming.


Amoxicillin is a newer version of penicillin. It stays in the body longer, better resists the effects of stomach acid, and kills more kinds of bacteria. It is better absorbed than the older antibiotic ampicillin.

Amoxicillin dosage for dogs

Amoxicillin is available in both tablet and oral suspension form. Dogs are prescribed 11-20 milligrams per kilogram of weight, administered two to three times a day. For example, a typical Labrador retriever that weighs 60 pounds would take 300 to 500 milligrams at a time.


Amoxicillin tablets are available in 50, 100, 125, 150, 200, 250, 400, 500, and 875 milligram sizes. Liquid amoxicillin should be refrigerated and discarded after 14 days. If a dose is missed, give a dose to your dog as soon as you can, but not if it's almost time for the next dose.

Dog amoxicillin vs. human amoxicillin

While the active ingredient in the drug is the same for both canines and humans, some of the additional ingredients like flavoring, artificial coloring, and preservatives in human amoxicillin can be dangerous for pets. For example, the sugar substitute xylitol can be toxic to dogs.


Amoxicillin side effects in dogs

As with any antibiotic for dogs, your pet may experience side effects, which can range from mild to life-threatening. The most common amoxicillin side effect in dogs is digestive tract upset, including vomiting, diarrhea, and lack of appetite.

A dog allergic reaction to amoxicillin can also include digestive upset, as well as hives, redness, swelling, and other skin reactions. In rare cases, a dog may experience anaphylaxis, a life-threatening condition in which he may have difficulty breathing and experience low blood pressure, seizures, and can slip into a coma. Also, some drugs may interact dangerously with amoxicillin. These include tetracycline, erythromycin chloramphenicol, and probenecid, as well as cephalosporins and aminoglycosides.


If your dog experiences side effects from amoxicillin, contact your vet promptly. She may adjust the dosage or prescribe a different antibiotic. If your dog is having trouble breathing or having seizures, take him to an emergency vet immediately. Also, you should not stop or start giving your dog amoxicillin without consulting with your vet first.

Antibiotic resistance

While amoxicillin can be an important treatment to rid your dog of infection, as with many antibiotics, it is over-prescribed. Sometimes a bacterial infection is confirmed, but often it is only suspected. The overuse of antibiotics can lead to antibiotic resistance, making it hard to find a drug that can effectively treat an infection.


If your dog's infection is not improving while taking amoxicillin, inform your vet. The infection may not be bacterial or may be resistant to amoxicillin. Either way, it's important to stop giving it to your dog rather than upping the dose or giving it to her longer.

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.