Ampicillin (Polyflex®) for Dogs and Cats


Overview of Ampicillin for Dogs and Cats

  • Ampicillin, also known as Polyflex®, is an antibiotic related to penicillin used in dogs and cats to treat and prevent bacterial infections.
  • As with similar penicillin drugs, ampicillin kills bacteria by inhibiting production of the bacteria cell wall. Other related drugs include penicillin G, amoxicillin and ticarcillin.
  • Many bacteria develop resistance to ampicillin.
  • Ampicillin is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • Brand Names and Other Names of Ampicillin

  • This drug is registered for use in humans and animals.
  • Human formulations: Totacillin-N® (SK-Beecham), Polycillin-N®, Omni-pen®
  • Veterinary formulations: Polyflex® (Fort Dodge), Amp-Equine® (Pfizer)
  • Ampicillin is supplied by numerous drug companies with a variety of trade names and various generic formulations.
  • Uses of Ampicillin for Dogs and Cats

  • Ampicillin is prescribed to treat or control infections caused by susceptible bacteria.
  • Infections treated with ampicillin often include wounds, skin infections, tooth abscesses and bladder infections.
  • Ampicillin is not effective against infections caused by viruses or parasites (such as worms).
  • Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, ampicillin can cause side effects in some animals.
  • Ampicillin should not be used in animals with known hypersensitivity or allergy to the drug.
  • Ampicillin may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with ampicillin.
  • It is common for animals to develop diarrhea or loose stools following treatment with oral ampicillin because this antibiotic can change the bacterial population of the pet’s intestinal tract. If your pet has diarrhea, notify your veterinarian. Ask if the medication should be changed.

    How Ampicillin Is Supplied

  • Ampicillin is available in 250 mg and 500 mg capsules and also comes in different liquid oral suspensions (liquids that should be gently shaken).
  • Ampicillin is also available in various injectable concentrations.
  • Dosing Information of Ampicillin for Dogs and Cats

  • Medication should never be administered without first consulting your veterinarian.
  • The typical dose of ampicillin in dogs and cats ranges from 5 to 10 mg per pound (11 to 22 mg/kg) three or four times a day.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.
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    Antibiotics & Antimicrobial Drugs



    Multiple organ systems can be affected
    Dentistry & Oral Cavity diseases
    Dermatology & Integumentary diseases
    Gastroenterology & Digestive diseases
    Hematology & Hemic-Lymphatic diseases
    Nephrology & Urology
    Neurology & Nervous System disorders
    Orthopedics & Musculo-Skeletal diseases
    Respiratory & Thoracic diseases


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