Exercise Caution: A Word from Victoria’s Vet About Chemical Castration

Photo: Dogster

Photo: Dogster

Zeuterinwhat is it and what is all the fuss about?

Zeuterin is an injectable sterilization product that is labeled for use on male dogs between 3 and 10 months of age. This sounds great, right? Sterilization without surgery? Any product that could potentially decrease the number of stray pets is fantastic. But hold your syringe, because as good as it sounds, it might not be as quick and easy as it has been portrayed.

Believe it or not, this is actually not a new product. It was first introduced into the market in 2003 under the name of Neutersol and subsequently pulled in 2004 because of supply problems according to the manufacturer. There were also some complications that the company contributed to “improper injection technique” due to lack of training.

The manufacturer relaunched the drug, now under the name of Zeuterin, and have instituted more intensive training for the veterinarians using the product. However, there are still some unanswered questions about the product, and significant concerns that I have, such as:

1. There are no long-term studies available at this point about pain which might be involved with the procedure (i.e., do the dogs feel pain long after the injection?), nor regarding lingering injection complications such as tumor formation. We surely do not want these dogs to be in pain or develop other diseases such as cancer because of the product.

2. I have concerns about the reduction of testosterone in dogs. A surgical neuter reduces the testosterone down to zero, while Zeuterin reduces it to about half the level of an intact dog. Having testosterone could cause these dogs to be more aggressive. More aggressive dogs could lead to more dog fights, and also human bites.

3. With the chance of increased aggression and more potential human bites, I have concerns that if Esterilsol (Zeuterin) became widely used in rescue dogs, an unintended consequence might be that people will become reluctant to adopt these dogs for fear of having a family member or child be bitten. This will lead to more dogs being euthanized in shelters.

4. It is critical to have proper administration of the product, and I am not certain there would be any cost savings as opposed to a surgical neuter after all costs are calculated. These costs would include training for the veterinarian, the cost of the drug, the sedative needed to allow the injection to happen, and the pain medication given after the injection. This is not just a quick and easy injection, such as vaccines. It requires measurement of the testicles to ensure the proper amount is administered. The company recommends light sedation for the injection, which needs to be given slowly – over 5-12 seconds per testicle. While the testicles do not have pain sensors, they do have pressure sensors and as the testicles are injected there is some discomfort, so pain medication is needed for these pets.

5. Proper identification is also important because it will be visually difficult to tell if the dog has been altered or not. Improper identification or identification that has worn away or is difficult to see (such as a tattoo) could cause problems and expense for the owners. They may not be able to board their dog, since most facilities will not board intact male dogs for liability reasons. The owner may incur expenses such as tests being run to see if we can tell if the product has been used on the patient or if he still needs to neutered.

6. Because the drug has a very narrow window of time in which it can be used (3-10 months of age), there is a risk that the drug might accidentally be used off label and expose those using the drug to liability and risk to the animals it is used on. Knowing a dog’s birthdate with certainty is rare. Once a dog is over four months old where the permanent teeth have erupted, it is very difficult to tell their age, and most of the time it is an educated guess. This is especially true in shelter and rescue dogs since many of them are malnourished and have medical problems, making it almost impossible to verify their exact age.

Therefore, while this product has great potential to help control the dog population, it might be too early to know if it will be as good as the manufacturer says it is. I would recommend caution when using the product for the next few years so that we can make sure we are not inadvertently harming the pet population. As with all new drugs and pet products on the market, only time will tell if it holds up to its original marketing claims.

Duffy Jones is Victoria's personal dogs' vet and a practicing veterinarian at Peachtree Hills Animal Hospital in Atlanta, GA.

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Positively Expert: Duffy Jones

Dr. Jones serves as the veterinary consultant for "It's Me or the Dog" episodes filmed in Atlanta. He received his Doctorate of Veterinary Medicine from the Tufts University School of Veterinary Medicine in 1999, and later opened Peachtree Hills Animal Hospital in Atlanta, GA in 2005.


8 thoughts on “Exercise Caution: A Word from Victoria’s Vet About Chemical Castration


    LOL. How does REDUCING testosterone levels by 50% "result in fighting and aggression" ??? Maybe you phrased that sentence poorly, but if anything, reducing testosterone by half will reduce aggressiveness, risk of prostate cancer, risk of testicular cancer, and completely eliminate the concern of all the health problems (bone cancers, etc) that come with neutering. I don't know if you're a physician or not, but our bodies were given hormones for a reason. They are an imperative part of normal function.

    Ever talk to a man who has insufficient testosterone? Depression, lethargy, weight gain, weakness, fatigue, higher risk of Alzheimers, Diabetes, cancers and heart problems. This is no different in animals. A procedure that leaves 50% of the testosterone in the system is not only better, its *ideal*. In fact it is excess testosterone that causes health problems. Mitigating those levels down to something more reasonable not only gives them testosterone to prevent health issues, but eliminates problems of excess T.

    The procedure is also not just for age 3 to 10 months. its used in all ages. This is just the typical neuter period for those uneducated about waiting for full development before castration. And its likely the age at which they conducted the trials, so they are legally only able to cite those ages in their documentation.

  2. K. Dwyer

    My Golden Lab was sterilized using Zeuterin at 9.5 months. We are now needing to have him castrated at 2.5 years, due to all the annoying intact male behaviors. I really regret not doing it the old school way in the first place. It would have saved us lots of money in training and our dog lots of frustration. I truly do not believe Zeuterin is a solution at this time!

  3. K. Dwyer

    My Golden Lab was sterilized using Zeuterin at 9.5 months. We are now
    needing to have him castrated at 2.5 years, due to all the annoying
    intact male behaviors. He sniffs and licks pee constantly, humps every
    dog he meets and is unable to participate in group dog play. His
    siblings were all neutered the traditional way and none of them have any
    of the annoying behaviors. I really regret not doing it the old school
    way in the first place. It would have saved us lots of money in training and
    our dog lots of frustration. I truly do not believe Zeuterin is a
    solution at this time!

  4. violater1

    It apparently did not work well at all in Mexico!!? Mexicos Dogs are still crossing our borders!!??!!! Oh! My Bad those are supposed to be humans!!!! Still Criminal animals as far as I can see!!!!!!

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