Amoxicillin, Clavamox®, and other Penicillins

Amoxicillin, Clavamox®, and other Penicillins


Penicillin was the first clinically applied antibiotic in medicine, and compounds related to it are in wide use today.  Amoxicillin and Clavamox® (also known as amoxicillin-clavulanate or Augmentin®) are frequently prescribed for home use in cats and dogs. The two medicines are related.  Clavamox® is more potent than amoxicillin.

Penicillins are used to treat a wide variety of infections in cats and dogs.   These include, among others: abscesses, bladder infections, skin infections, respiratory infections, dental infections, and infected wounds.


Amoxicillin and Clavamox® are both readily available as pills or as liquid suspensions. Liquid Clavamox® should be refrigerated.

Various injectable penicillin formulations are used by veterinarians in the hospital setting. Injectable formulations are prescribed for home use in rare instances.

Side Effects

Like all antibiotics, gastrointestinal upset (nausea, diarrhea, vomiting, or loss of appetite) is the leading side effect of penicillins. In some individuals, Clavamox® may be more likely than amoxicillin to lead to side effects.  The risk of side effects may be reduced by giving the medication with food.  Ask your veterinarian whether this is appropriate for your pet.

The gastrointestinal side effects of penicillins generally get worse over time if the medicine is not discontinued. If you suspect that your pet is experiencing side effects, contact your veterinarian immediately.  Do not discontinue any antibiotic without first consulting a veterinarian.

Although severe allergic reactions to penicillins are a major concern when they are used in humans, these reactions are much less common in pets.  Signs of allergic reactions include skin rashes, weakness, swelling of the face, or difficulty breathing.  Seek immediate veterinary attention if you suspect that your pet is suffering an allergic reaction to any type of penicillin.


Pets should be monitored for side effects and for resolution of symptoms.   Unless otherwise instructed by a veterinarian, pets should continue to take the medication until the entire course has been completed.

Long-term (greater than 14 days) use of penicillins is uncommon.  Any pet that receives long-term medications may require periodic blood or urine testing.

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The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.