Cefazolin Injection

Information from PetPlace, by Dr. Dawn Ruben.

Overview of Cefazolin for dogs and Cats

• Cefazolin is an antibiotic, commonly known as Kefzol® and Ancef®, of the cephalosporin class. It is related to the penicillin drugs in how it kills bacteria, but cephalosporins have a much broader range of activity against bacteria than penicillins. Cefazolin is used in both dogs and cats to treat a variety of bacterial infections, including skin infections, wound infections, bone infections, pneumonia and bladder infections
• Cefazolin will prevent the bacteria from forming an adequate and protective cell wall. This results in instability and subsequent death of the bacteria.
• Cefazolin is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
• This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names of Cefazolin

• This drug is registered for use in humans only.
• Human formulations: Kefzol® (Lilly), Ancef® (SKF), Zolicef® (Apothecon) and various generic preparations
• Veterinary formulations: None

Uses of Cefazolin for Dogs and Cats

• Cefazolin is used in both dogs and cats to treat a variety of bacterial infections, including skin infections, wound infections, bone infections, pneumonia and bladder infections.
• Cephalexin is not effective against infections caused by parasites (intestinal worms), mites, viruses, or fungi.
• Cefazolin is only available in injectable form and is typically administered in a hospital setting.

Precautions and Side Effects

• While generally safe and effective when prescribed by a veterinarian, cefazolin can cause side effects in some animals.
• Cefazolin should not be used in animals with known hypersensitivity or allergy to the drug.
• If a pet is already sensitive to allergy or vomiting from other cephalosporin drugs (cefadroxil) or penicillins (amoxicillin, ampicillin), cross-reaction with cefazolin is possible.
• Cefazolin may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with cefazolin. Such drugs include certain other antibiotics.
• The most common side effect in animals is vomiting shortly after administration. It is usually not a sign of serious disease, but indicates that the pet is sensitive to this drug.
• It is not unusual for some animals to develop diarrhea from orally administered antibiotics such as cefazolin. However, this has not been a common complaint with cefazolin.

Information from Plumb's Veterinary Drug Handbook, 7th Edition, by Donald C. Plumb:

Cephalosporins are contraindicated in patients with a history of hypersensitivity to them. Because there may be cross-reactivity, use cephalosporins cautiously in patients who are documented hypersensitive to other beta-lactam antibiotics (e.g. penicillins, cefamycins, carbapenems). Patients in renal failure may need dose adjustments.

Adverse effects with the cephalosporins are usually not serious and have a relatively low frequency of occurrence. Hypersensitivity reactions unrelated to dose can occur with these agents and can manifest as rashes, fever, eosinophilia, lymphadenopathy, or full-blown anaphylaxis. 

Cephalosporins can cause pain at the injection site when administered intromuscularly, although this effect occurs less than with other agents. Sterile abscesses or other severe local tissue reactions are possible, but much less common. Thrombophlebitis is also possible after IV administration of these drugs. 

While cephalosporins (particularly cephalothin) have the potential for causing nephrotoxicity at clinically used doses in patients with normal renal function, risks for the reoccurrence of this adverse effect appear minimal. 

High doses or very prolonged use has been associated with neurotoxicity, neutropenia, agranulocytosis, thrombocytopenia, hepatitis, positive Comb's test, interstitial nephritis, and tubular necrosis. Except for tubular necrosis and neurotoxicity, these effects have an immunologic component. Cefazolin may be more likely than other cephalosporins to cause seizures at very high doses (usually very high doses given IV rapidly).

Cephalosporins have been shown to cross the placenta and safe use during pregnancy has not been firmly established, but neither have there been any documented teratogenic problems associated with these drugs. However, use only when the potential benefit outweighs the risk. Cefazolin is distributed into milk and could potentially alter neonatal gut flora. Use with caution in nursing dams. 

Cefazolin may have interactions with the following drugs: nephrotoxic drugs, probenecid.