Antibiotics for mastitis in dogs

mother dog with puppy image by Phaedra Wilkinson from

Mastitis presents as a bacterial infection of the mammary glands in nursing mother dogs and constitutes a veterinary emergency for the health of the mother and her puppies. Symptoms typically include one or more painful inflamed teats, possible sores and abscesses on the infected gland.

The milk from the diseased teat usually appears abnormal in colour and consistency due to the bacteria. In subclinical or chronic mastitis, the only presenting symptoms in the mother may be the failure of the puppies to thrive. Most veterinarians recommend a broad-spectrum, systemic antibiotic to be administered over a period of several weeks to cure the disease, according to the Merck Veterinary Manual.


Veterinary pharmacologists classify amoxicillin/clavulanate (trade name Clavamox) in the same family of drugs as penicillin. The bacterium causing your dog's mastitis produces enzymes called B-lactamase that normally deactivate most penicillins by destroying part of the drug's molecule. By combining the penicillin drug amoxicillin with potassium clavulanate to produce Clavamox, those enzymes are deactivated, and the bacteria destroyed, maintains Dr. Robert Bill in "Pharmacology for Veterinary Technicians."

Clavamox works by interfering with the development of the bacterial cell walls, causing them to lyse (explode). Your veterinarian will typically prescribe Clavamox in either tablet or liquid suspension form, with a recommended dose based on your dog's weight. The liquid suspension must be kept refrigerated for the duration of the treatment to maintain its efficacy.

Because penicillin-type drugs pass into mother's milk, vets typically recommend that nursing puppies be hand-fed until the infection is cured and the antibiotic is no longer in the mother's system. Timing will vary depending on the severity of the infection, the age of the puppies, and the amount of drug dispensed.


Unlike Clavomox, cephalexin (trade name Keflex) doesn't transfer into mother's milk and is considered safe to use in nursing bitches, says Dr. Wendy Brooks, The Pet Pharmacist of Veterinary pharmacologists refer to cephalexin as a first-generation cephalosporin, meaning that it was in the first group of drugs developed to be effective against penicillin-resistant bacterium. Vets commonly prescribe cephalexin, a human drug used off-label for canine patients, to combat the bacteria causing mastitis, bladder infections and deep skin infections.

Cephalexin kills bacteria in much the same way as penicillins, by destroying cell walls that permit the rapidly growing bacteria to live and multiply. Dogs readily absorb this medication from the intestinal tract with few side effects and rare instances of cephalosporin-related allergies, states Dr. Mark G. Papich in "Saunders Handbook of Veterinary Drugs."

Available in tablet, capsule and liquid forms, your veterinarian will recommend a dosage and the length of treatment depending on your dog's weight. This liquid medication also needs to be refrigerated.

Cloxacillin, dicloxacillin, oxacillin

Veterinarians consider cloxacillin, dicloxacillin and oxacillin acceptable alternatives to Clavamox and cephalexin to treat mastitis. Particularly resistant to the B-lactamase enzyme produced by staphylococci bacteria, vets selectively will prescribe these antibiotics when dealing with a chronic or recurring mastitis infection or when previous antibiotics no longer seem to be working, according to Robert Bill.