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What Antibiotics are Used for Dog Pyometra?

Dog Pyometra

If your unspayed dog has been diagnosed with pyometra or you suspect your dog has this condition, you may be wondering what antibiotics can be used for pyometra. Pyometra in dogs is a serious medical condition which, left untreated, can become quickly life threatening. If you suspect your dog has pyometra, the best course of action is to the see the vet immediately. Pyometra can be diagnosed through x-rays or ultrasound. If your dog was diagnosed with pyometra but you are looking for alternative treatments other than surgery, consider that the use of antibiotics alone have poor success rates, but in certain specific circumstances, there are chances they can be used in conjunction with other drugs.

sun set

A Life Threatening Condition 

Pyometra is a condition that you do not want to underestimate because, left untreated, it will progress and become life threatening. Many times, the condition is not readily recognized by dog owners. The intact female dog goes off food and starts vomiting or gets diarrhea and the symptoms are passed for just a mild indigestion. Fast forward a few hours or a few days, and the dog has become lethargic and is already in critical condition.

Vet offices do not take their chances when they receive phone calls from owners describing intact female dogs (especially older dogs!) displaying vague symptoms of digestive problems, loss of appetite or increased thirst. They therefore recommend to take the dog immediately in to rule out this deadly condition.

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Indeed, among veterinary staff there is a special saying "Don't let the sun set on a pyometra" which suggests having affected dogs seen the same day, especially when they are already quite ill and unstable, but what is it that makes dog pyometra so deadly?

Introduction of Bacteria 

dog stalk

Pyometra is the term used to depict a dog's infected uterus filling up with pus which takes place after a heat cycle. Generally, the onset of pyometra symptoms are seen anywhere from 4 to 12 weeks following a heat cycle, explains Dr. Margaret V. Root Kustritz, a veterinarian specializing in animal reproduction.

Normally, a female dog's cervix (the lower part of the uterus) is tightly closed when the dog is not in heat, but during the heat cycle the dog's cervix remains open and this is when opportunistic bacteria may be introduced to the uterus. To further add insult to injury, consider that, heat after heat, changes in the lining of the uterus take place (cystic endometrial hyperplasia) due to the effect of the hormone progesterone, and this contributes to making the area more hospitable to bacteria. Soon, there is significant inflammation which causes accumulation of pus in the uterus and significant swelling as seen in the picture.

How severe the symptoms of dog pyometra become vary based on whether the dog suffers from an open or closed pyometra. In an open pyometra, the cervix remains open, allowing excess pus to exit. The discharge is often described as being foul-smelling and of a pale red color. Dogs with closed pyometra, on the other hand, show more severe symptoms as the pus has no way to escape causing complications such as secondary kidney disease and an enlarged uterus.

Death in dogs with pyometra occurs from shock due to "endotoxemia" which occurs when toxins and bacteria leak from the the uterine walls and into to the dog's blood stream.

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The preferred treatment for open or closed pyometra is ovariohysterectomy surgery, which consists of removing the uterus and the ovaries. Dr. Kustritz believes that there is no other ethical treatment available for female dogs affected by closed pyometra. Dogs with closed pyometra are at risk for rupture of the uterus and sepsis from bacteria getting into the blood stream.

Medical therapy using medications however may be an option in cases of very mild, early onset of open-pyometra when the dog is young and valuable for breeding (and owners do not wish to spay) and there are no signs of organ failure or toxic waste products in the blood.

Therapy in these cases consists of antibiotics along with prostaglandin injections meant to cause the dog's progesterone production to drop so to start uterine contractions and consequent expulsion of infected contents from the uterus. Antibiotics alone will not treat a dog's pyometra. In order to work, antibiotics need to be given with prostaglandins so that the uterus contracts and expels the pus, points out veterinarians Dr. Rebecca. 

On top of that, antibiotics for dog pyometra often fail to work well because they have difficulties penetrating into the uterus when it's full of pus. It's like trying to treat appendicitis with antibiotics, further points out veterinarian Dr. Rebecca.

" This form of treatment is not an option in the event of a closed pyometra because the closed cervix prevents drainage of the infected material even in the face of prostaglandin contractions. "~ Dr. Wendy C. Brooks

Antibiotics for Dog Pyometra 

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Good antibiotic choices for dog pyometra are amoxicillin-clavulanate, or a combination of a penicillin and a fluoroquinolone, explains Dr. Jeff Dennis and Dr. Brian Lucas Hamm. These drugs are typically prescribed for seven to 14 days while protglandin injections are typically given for 2 to 7 days. Affected dogs treated generally start showing signs of improvement generally within two to four days following treatment.

As reassuring as it may feel to see the affected dog improve, it's important to consider that dogs who develop pyometra are prone to getting it again and the risks repeat at every heat cycle. If dog owners wish to breed their dogs, it's recommended that they do so after treatment on the next heat cycle and then proceed to have the dog spayed as soon as possible while the dog is still healthy and in good spirits.

Spaying a dog when it has a recurrence of pyometra can mean having surgery on a dog that is very ill and this means more risks of complications. Also, the cost of a routine spay when the dog is healthy is much less costly compared to the cost of spaying a dog suffering from pyometra. For example, a routine spay may cost anywhere between $100-$500, while a pyometra spay can cost from $1,000 to $3,000!

 " Antibiotics cannot penetrate the uterus full of pus. It is like trying to treat appendicitis in people with just antibiotics, it just usually is not enough. People with appendicitis and dogs with pyometra need surgery, the soon the better."~Dr. Rebecca


  • DVM360, Frequently asked questions about small-animal reproduction (Proceedings)
  • DVM360: Surgical and medical treatment of pyometra

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