Veterinarians at the GVMA are always interested in products that could help to control the pet population.  However, we are equally concerned about the safety and unintended consequences of these products as well.  Below is a list of the GVMA’s concerns about Esterilsol (Zeuterin) for you:

1.    There are no long-term studies available at this point about pain which might be involved with the procedure (i.e., do they 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.    We 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, we 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 we are 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.

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 are 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 to 10 months), there is a risk that veterinarians might accidentally use the drug off label and expose themselves to liability.  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. 


Important Note

As with any medication or medical procedure, it is important to consult your veterinarian to determine the best treatment option for each individual patient. Though Esterilsol (Zeuterin) is an FDA approved medication the administration of the drug constitutes a medical procedure and it should be provided by, or under the supervision of, a licensed veterinarian.


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