Is Zeuterin a Good Choice For Your Dog?

I recently filled you in on my experience learning to use Zeuterin, a zinc/arginine solution used to nonsurgically neuter male dogs. Now, I’d like to enhance your understanding of the differences between surgical neutering and Zeutering.

Comparison of techniques

Surgical neutering of male dogs involves removal of both testicles (castration). A skin incision is made that is closed with stitches or staples. Unless the stitches are “buried” a follow up visit to remove staples or stitches is needed.

Zeutering involves injection of a small volume of Zeuterin into each testicle. There is no need for a follow up visit.

Sterility (inability to reproduce)

Sperm cells are manufactured within the testicles, so it makes sense that removing them results in sterility. Zeuterin induces sterility by causing formation of scar tissue that impairs the ability of sperm to leave the testicle.

Dogs are not considered to be 100% sterile until 30 days following surgical neutering and 60 days following Zeutering.

Post-procedure complications

Complications most commonly associated with surgical castration include:

  • Licking at the incision site
  • Surgery site discomfort/pain
  • Hematoma formation (blood accumulation) within the scrotum
  • Incision site inflammation/infection
  • Dehiscence of the incision (the stitches or staples loosen and the incision reopens)
  • Complications associated with general anesthesia

The more common complications associated with Zeutering include:

  • Licking at the scrotum
  • Swelling of the scrotum
  • Scrotal discomfort/pain

No studies have been performed directly comparing rates and severity of complications associated with surgical neutering versus Zeutering. Based on how both procedures are performed, it is fair to say that complications arising from general anesthesia and creation of a surgical incision are non-issues for dogs sterilized with Zeuterin.


In theory, the overhead costs for Zeutering should be significantly less than those associated with surgical neutering. Zeuterin is relatively inexpensive to purchase. Additionally, Zeutering does not require fees typically associated with surgical castration such as: placement of an intravenous catheter, anesthetic drugs, sterilization of surgical instruments, surgical mask, sterile gloves and gown, operating room maintenance costs, hospitalization, and a follow up office visit.

Keep in mind that the cost of surgical castration is deeply discounted in many veterinary clinics so as to capture the attention of price-shopping clients. In such clinics, the costs of surgical neutering and Zeutering may be comparable.

Testicular tumors

Testicular tumors are extremely common in older dogs, and 85 to 90 percent of them are completely benign. The risk for developing a testicular tumor is eliminated in dogs who are surgically castrated. The incidence of testicular tumors in Zeutered dogs is not known.

Prostate gland disease

Elimination of testosterone production via surgical castration prevents future development of benign prostate gland diseases such as prostate gland hyperplasia (age-related prostate gland enlargement that resembles what men experience as they age) and bacterial infection within the prostate gland (bacterial prostatitis). However, surgical castration is associated with an increased incidence of prostate gland cancer in dogs compared to dogs who have not been neutered.

There are no studies documenting how Zeuterin influences the incidence of the various types of prostate gland disease. What is known is that the size of the prostate gland decreases shortly after Zeutering, likely a result of decreased testosterone production.

Impact on testosterone production

Surgical neutering reduces a dog’s ability to produce testosterone by essentially 100%. Zeuterin reduces testosterone production by approximately 50%.

Elimination of testosterone production altogether via surgical castration has been the ruling dogma for several decades with the notion that doing so eliminates undesirable male behaviors and ensures better health (less benign prostate gland disease, prevention of testicular tumors, decreased trauma incidents associated with dogs who are roaming, etc.). A 1976 study evaluating 42 dogs documented that elimination of testosterone via castration reduces urine marking, roaming, mounting behavior, and dog-on-dog aggression.

More recent research documenting the effects of surgical castration has opened our eyes to some significant downsides associated with elimination of a dog’s ability to manufacture testosterone. Studies performed on Rottweilers, Golden Retrievers, Labrador Retrievers, and Vizslas demonstrated increased risk of significant orthopedic issues, various cancerous conditions, and challenging behavioral issues associated with removal of the testicles, particularly before one year of age. (Many of the same negative consequences apply to spaying female dogs.) Whether or not the results of these breed-specific studies can be translated to “dogs in general” is anyone’s guess.

Also unanswered to date is whether or not Zeuterin induced “half-strength” testosterone production is protective against the recently documented negative health and behavioral issues associated with surgical castration. Additionally, how Zeuterin influences negative male behaviors (urine marking, roaming, mounting, dog-on-dog aggression) is unknown.

Research is needed to answer these questions and more pertaining to the pros and cons of different neutering practices. We have a great deal to learn! And, the more we learn, the more we will question currently accepted standards pertaining to neutering dogs.

Is Zeuterin the right choice for your dog?

Whether to surgically neuter or Zeuter your dog should be based on discussion with your veterinarian and consideration of your dog’s age, breed, and behavior.

Would you consider Zeuterin for your dog? If you have questions about Zeuterin, please ask away.

Best wishes,

Nancy Kay, DVM

Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
Become a Fan of Speaking for Spot on Facebook

Please visit to read excerpts from Speaking for Spot and Your Dog’s Best Health.   There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at,, local bookstores, and your favorite online book seller.


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6 Comments on “Is Zeuterin a Good Choice For Your Dog?

  1. I have frequently used the words “spay” and “neuter” (now “Zeuter”) in everyday conversation. But, I did not stop to think deeply about the pain caused to my 2 spayed dachshunds! I have been thinking deeply (finally!) about not sterilizing our next puppy.

    I take a pledge to diligently and responsibly supervise my next adopted dog so that there will be no compelling reason to neuter.

    I enjoy Dr. Nancy’s blogs because they are so educational!

  2. Hi Dr. Kay!

    I was a member of the team hired to produce the marketing materials for Zeuterin. As such, I read all the data and chose to have my own dog “Zeutered.” The reason I did it — and would likely choose this option again — is the chance of keeping some testosterone in the system of my male dogs. I believe many of the behavior problems”with intact males can be handled through training and management, aside from dog-dog aggression. My two breeds — Sheltie and Flat-Coated Retriever — are not known for dog aggression, but if I had a breed that did have a problem with this, I would factor that in and maybe a different decision for an individual animal.

    My Sheltie was ‘zeutered” 18 months ago. (My Flat-Coat is a bitch, lap-spayed and pexy’d years ago.) NED experienced some initial swelling and redness, but it was short-term (week to 10 days, maybe). His testicles are now quite small, maybe 15% to 20% of their initial size. I haven’t had his fertility tested, but I’m presuming he’s sterile. His nice neon-green “Z” tattoo is as sharp as the day it was done. His temperament is normal for his breed.

    Honestly, if I couldn’t preserve some testosterone, I would be very hesitant to neuter at all. I am always mystified that people who stress over how unnatural “chemicals” are seem to have no problem with the unnaturalness of surgically removing a piece of an animal’s anatomy. I also wonder at people questioning the “invasive” aspect of a needle. I suppose castrations are done with a magic wand, not a scalpel!

    My consulting work with the company is long over, but I still believe in Zeuterin, based on my reading all the materials. That said, I am looking forward to more research in this area, and would prefer to keep my male dogs intact for their health.


  3. Great comments Susan. The main reason to neuter a male dog is to help prevent unintentional litters/pet overpopulation. For the male dog who is diligently and responsibly supervised there is no compelling reason to neuter.

  4. My boy is now an elder gentleman (12 and a giant breed), and he was never neutered. No puppies, planned or unplanned, no behavioral issues. With responsible ownership and training, it seems to me that neutering is a non issue, unless some compelling medical reason arises to recommend it. For male dogs, at least. I guess my message to owners of male dogs is that an unneutered male is not automatically dangerous or unmanageable. If you are willing to be diligent, the decision to neuter is an option but not a necessity. As with most issues involving dogs, it is the owner who is most important for having a good result.

  5. Hi Janet. Thanks for your thoughtful comments and questions. I am not at all averse to leaving male dogs intact, but only with the major caveat that the dogs are handled responsibly. In my mind, this means that they are not allowed to breed other dogs unless the breeding is intentionally planned. If the intact dog develops benign prostate gland disease or testicular tumors, he can be neutered later in life.

  6. If an older intact male can be neutered if and when it develops a testicular tumor (which it sounds like most Are benign) and surgical neutering is shown to actually increase the risk of prostate gland cancer later on, and there are no long-term studies to know the effect of chemical castration on a dog down the road, would it not be a reasonable and logical alternative, at least for a responsible dog owner,
    to keep their male dog intact? A responsible dog owner does not let their dog roam, and is attentive to their physical health and mental training and well-being, so would it not be in the best interest of the individual dog to be left intact unless and until there is an actual health related reason to neuter?

    With regards to chemical castration, personally I would be more comfortable staying with surgical castration until such time that long-term studies show that chemical castration is not going to create health problems down the road. That said, I can see benefits for chemical castration particularly in other countries where there are massive problems of stray dogs roaming the streets etc. and possibly even in high volume shelters even in this country, as a cost savings move. Even then I would only partially be in favor, because I think in a perfect world the long-term health of the individual animal should be priority. But then I am also not in favor of pediatric spay or neuter which is so popular these days. Not saying that I am right about that, it is just a personal feeling.