Major Uses

Ampicillin is an antibiotic used to treat infections brought on by bacteria. Very similar to penicillin and amoxicillin, the drug destroys bacterial infections by preventing the cell wall of bacteria to grow. Ampicillin covers a broad spectrum of bacteria, but resistance to the drug can occur. Because the drug is known to be safe, it can be prescribed to most species. Examples of what ampicillin might be prescribed to treat include skin and wound infections, urinary and bladder infections, tooth abscesses, and pneumonia.

Common Precautions

Adverse reactions can occur, even if the medication prescribed is safe like ampicillin. Common side effects include vomiting, diarrhea, and loss of appetite. If these symptoms persist, the pet's veterinarian should be contacted. Possible drug interactions can occur, so the prescribing veterinarian should be informed of all medications, vitamins, and supplements the pet is taking. Other antibiotics, such as tetracycline, and blood thinners can interact with ampicillin.

Ampicillin should not be prescribed to animals with a known allergy or hypersensitivity to the drug. Signs of an allergic reaction include swelling of the face, scratching, hives, and seizures. The pet's veterinarian should be contacted immediately if these signs are exhibited.


Ampicillin should be stored in a childproof container, impervious to light. Typically, oral suspension forms are refrigerated, however, it is suggested that the manufacturer storage directions are closely followed.


Ampicillin is found in capsule and liquid suspension form. Dosage will vary depending on the severity of the infection and the susceptibility of bacteria. A Typical dose for dogs and cats is 5-10 mg/lb (10-20 mg/kg) every 6-8 hours intravenously (IV), intramuscularly (IM), or subcutaneously (SC). A typical dose in capsule form is 10-20 mg/lb (20-40 mg/kg) by mouth every eight hours. For horses, a typical dose is 3-10 mg/lb (6.6 - 20 mg/kg) every 6-8 hours either IM or IV. Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose is missed it should be taken as soon as possible, unless it is almost time for the next dose. If it is almost time for the next dose, the missed dose can be skipped and the regular dosing schedule should be followed; two doses should not be given at once. The prescribing veterinarian should be contacted if there are any questions or concerns.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.