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Penicillin treats an array of bacterial infections in dogs. There are many different forms of penicillin, including penicillin G, penicillin V, amoxicillin, and others. Keep reading to discover everything you need to know about penicillin for dogs, including dosage, drug interactions, and other considerations.

Dosage

Penicillin is most often administered via injection, but it’s also available as a tablet, liquid, or gel. Penicillin tablets are best given on an empty stomach. If vomiting or nausea occurs, give penicillin with food.

The dosage amount will vary based on the type of penicillin, as well as your dog’s age and condition. Always follow your vet’s dosage instructions. Never discontinue a course of antibiotics before it runs out unless your vet explicitly instructs you to do so.

Efficacy

Certain strains of bacteria are resistant to penicillin, which is why it’s often combined with other broad-spectrum antibiotics. Amoxicillin is one of the most effective penicillins in treating urinary tract infections, as well as skin, ear, and oral infections. Amoxicillin is often combined with clavulanate to target penicillin-resistant bacteria.

Side effects

Side effects of penicillin for dogs are rare and may include:

Considerations

Some bacteria are resistant to penicillin, so it may be prescribed with other antibiotics. Vets will usually only prescribe penicillin only in cases where the bacterial strain is known to be susceptible to penicillin.

Drug interactions

Certain kinds of penicillin can alter lab test results. Be sure to let your vet know if your dog is taking penicillin or other medications, including over-the-counter drugs. 

Drugs that may interact with penicillin for dogs include, but are not limited to:

  • Other antibiotics

  • Immunosuppressive drugs (methotrexate)

  • Drugs that treat gout and uric acid stones (probenecid)

Allergic reactions and sensitivity

Some dogs are allergic to penicillin. Consult your vet immediately if you notice any of the following signs of an allergic reaction:

  • Rash

  • Fever

  • Facial swelling

  • Labored breathing

Frequently asked questions

Do I need a prescription for penicillin?

Yes. Penicillin is a prescription-only drug.

Is it possible for my dog to overdose on penicillin?

While overdose is incredibly rare, it is possible. Keep all medications out of your dog’s reach and never give them more than the prescribed dose.

My dog’s symptoms are clearing up. Is it okay to stop giving them penicillin?

Never discontinue a course of antibiotics early, even if your dog seems to be feeling better. This could increase antibiotic resistance, which could cause the infection to return.

What should I do if I miss a dose?

Give the missed dose as soon as you remember, unless it’s within 2 hours of the next dose. In this case, skip the missed dose and resume the normal dosing schedule. Never double up on doses or give extra doses.

My dog has taken the full course of antibiotics, but their symptoms aren’t improving. What should I do?

If your dog’s condition doesn’t improve, contact your vet. A penicillin-resistant strain of bacteria may be responsible for the infection.

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