Zeuterin: Chemical Sterilization of Male Dogs

Photo Credit: Shirley Zindler


I first wrote about Zeuterin, a product used to chemically sterilize male dogs, a couple of years ago. At the time, Zeuterin was still undergoing studies for FDA approval. Ark Sciences, the manufacturer of Zeuterin, received that approval in early 2014, and, since then, the use of this product has rapidly accelerated within the United States.

I recently completed the specific training required for veterinarians to purchase and use Zeuterin. My training began with an online instructional webinar. Next, I completed a wet lab during which I Zeutered three dogs under the watchful eye of a certified trainer. I had the good fortune of doing so with certified trainer, Dr. Laureen Bartfield. She is the director of SNAP-NC (Spay Neuter Assistance Program of North Carolina), and has Zeutered hundreds if not thousands of dogs.

The Zeutering process

From start to finish, Zeutering each dog required no more than 10 to 15 minutes. Keep in mind, things would have been easily twice as quick had I not been learning the procedure for the first time. Here’s how the Zeutering worked:

Step one: Each dog received a thorough physical examination to make sure there were no problems that would interfere with a good outcome. For example, if a dog had significant skin irritation around the scrotum, he would have been disqualified from being Zeutered that day.

Step two: Each dog was sedated to very lightly anesthetized. The goal was to sedate to the point that the dog was willing to lie on his back without struggling. We used a sedation drug called dexmedetomidine, the effects of which were readily reversed by another drug immediately following the procedure.

Step three: Using calipers, the size of each testicle was measured in order to determine and draw up the exact volume of Zeuterin needed for each testicle into two separate syringes.

Step four: Using a slow, steady technique, the appropriate volume of Zeuterin was injected into the center of each testicle. Pain receptors within the testicles respond primarily to changes in pressure, so the key to keeping the dogs comfortable was injecting the Zeuterin very slowly.

Step five: A green “Z” was tattooed within the skin adjacent to the sheath (just in front of the scrotum). Given that the testicles remain, this tattoo announces to the world that the dog has indeed been neutered.

Step six: The dogs were sent home within a couple of hours of being Zeutered. They received an injection of pain medication along with a few day’s worth of oral pain medication to be given at home. This is a standard recommendation for dogs who have been Zeutered. There is no need for a follow up visit unless concerns arise. Clients were advised that their dog would have some scrotal swelling for the first few days. They were also told that their dogs would not be 100% sterile until 30 days following Zeutering.

Impressions of Zeutering

Following my first hands on experience with Zeuterin, here are my impressions:

  1. The Zeutering process is precise, but easy to learn.
  2. Zeutering is a quick process.
  3. Zeutering is a safe process.
  4. The Zeutering process appears to be pain-free.
  5. Recovery from Zeutering is rapid.
  6. Zeuterin provides a safe and effective means to neuter male dogs.

Stay tuned for Zeuterin: Part II in which I will compare Zeutering to conventional surgical neutering.

Would you consider Zeuterin for your dog?

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
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Please visit http://www.speakingforspot.com 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 www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.


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26 Comments on “Zeuterin: Chemical Sterilization of Male Dogs

  1. Thank you for the detailed report on this intriguing procedure. I look forward to learning more in part II.

    In my roles as a Pet Wellness Coach, humane society medical volunteer, and rescue volunteer, I’ve encountered many attitudes about neutering, and have seen many of the positives and negatives of surgical neutering.

    Zeutering is well worth considering. Some of the main concerns have already been addressed by others, the largest of which is the long term effects, both positive and negative.

    While surgical neutering is generally safe and effective, I’ve seen first-hand what can happen when things don’t go well. Fortunately, in nearly all cases, any negative reactions, infections, and other effects can be improved with time and a little TLC. But it’s difficult for owners and care providers during that time, and especially difficult for the dogs who are dealing with the physical, mental and emotional processes of healing.

    The attitudes and fears that some people have about neutering present challenges. Education can help, but doesn’t in all cases. For some people with a negative attitude, non-surgical castration may be a good solution.

    At this time, I can’t say that I will or will not recommend Zeuterin to my clients. A little more information is needed to really feel comfortable with that. However, it will certainly be on the top of the list of things to suggest to anyone who adamantly opposes surgical neutering.

    Because overpopulation is a real problem, it’s great to see at least one additional option available.

    Let’s all continue to communicate, educate, and promote responsible decisions among pet guardians.

  2. Hi Nancy. Thanks for expressing your concerns and questions. The purpose of FDA approval is to determine that a drug is safe for use. Of the thousands of dogs who have received Zeuterin, only a few have experienced a negative reaction such as significant inflammation of the scrotum. These dogs were then surgically neutered. The likelihood of such a dramatic reaction is very, very small. I hope this helps answer your question and concerns.

  3. I have concerns. What is the dog has a bad reaction to the drug. Once it is injected, it can not be removed. What are the long term effects of this drug?

  4. Hi Meg. Zeuterin is licensed for use on dogs who are three to 10 months of age. It can certainly be used safely in dogs over 10 months of age, but this would be considered an “off label” use.

  5. How old does the dog need to be eliglble for this procedure? I’d do this with a pup but hesitate with a sexually mature dog….30 days is a looooong time!

  6. Hi Sonia. Thanks for your comments and questions. Part of getting FDA approval for Zeuterin was providing proof that it is safe and fully effective. Castration involves general anesthesia. Zeuterin does not. Castration is a surgical procedure. Zeuterin involves no surgery whatsoever. This means that a dog who is Zeutered is not subject to the complications that can be associated with general anesthesia and surgery. In my mind, these are compelling reasons to use Zeuterin. I would not hesitate to Zeuter a dog of mine.

  7. I can see why rescues would want to use this method but I still don’t like the idea as general protocol. Is there a reason why this method should be promoted to pet owners? Is there some statistic that says this is safer , more beneficial or will get more owned pets neutered? Perhaps cost? How do you know for sure that it is fully effective?

    I am sure there are men out there that are happy that their boys can keep their “boys”.

  8. Grant. I spoke with the folks at Ark Sciences about your AKC question. Here is what they had to say. AKC considers zinc neutered dogs altered and they should not be shown as intact dogs in conformation classes.

  9. Thanks for your questions Grant. The testicles do ultimately shrink to a size slightly smaller than they were to begin with. Your question about the AKC’s point of view is a great one, and I don’t know the answer. I suspect that Zeutered dogs would be regarded like a surgically neutered dog. I will dig around and see what I can find out!

  10. I understand that the testicles remain and return to normal size soon after the procedure, correct? Where is AKC with sterilization but leaving testicles intact for show dogs?

  11. Thanks for your comments and questions Lisa. Yes, I used dexdomitor (dexmedetomidine) for sedation, but this was simply a matter of personal preference. Other sedatives can be used. You are correct, complications can arise with any medication used.

  12. Was Dexdomitor used to sedate?
    One of my dogs had a bad reaction to Dexdomitor.
    I am told that such reactions are not common, but they can happen.

  13. As a rescuer, I think I prefer removing the testicles. Easier to see the dog has been neutered, and eliminates testicular cancer. While I highly and like respect Dr. Bartfield,( met her on SNAP and while working at Wake County Animal Center), I still wonder what the long term effects might be.

  14. Yes, I would Zeuterin my dog? Great news for male dogs!

    Caveat: I would worry a lot about some nonprogressive vets in my area (Texas) not knowing that the green “Z” tattooed means my dog was Zeutered.

  15. I think this is a good procedure from what you posted. One concern I had was with the green tattoo. Green tends to fade with time. Black is the best long lasting color for tattoos.

  16. Wonderful idea–just need to train more people to do this.

  17. Hi Judy. To date, there are no studies demonstrating the impact of zinc versus surgical neutering on the incidence of cancers, orthopedic issues, and behavioral problems as identified in the breed specific studies you mentioned.

  18. I would be thrilled to have zeutering available to me. However, the speed with which the approval process for dogs more than ten months old is moving leads me to believe my boy will be in his dotage before it is oked. This makes me wonder why the process is not expedited due to the alleged dog overpopulation crisis (which allows the local powers that be to demand absurd licensing fees to keep my animals intact, while importing animals from out of state to fill the demand for small, cute puppies). Sheeeesh.

    That aside, and in light of the golden/rottie/viszla studies showing the deleterious effects of too-early neutering, how does zinc neutering shape up in that respect? Any studies? Any opinions?

  19. Hi Mary Lee. The cost for Zeutering will depend on how much the product is marked up by the veterinarian using it. Ask your veterinarian to provide you with a cost comparison.


  21. No, I would not use this on my own dogs and I would not commend against it, either. I am not convinced that Zeuterin is safe.

    I can see where something this might have a place in population maintenance, ie, feral dogs, wolves, coyotes, and fox, but I don’t see it taking off in the personal pet market

    Surgical alterations have been done for almost ever, and the lifetime effects of that procedure are not fully known and hotly debated. Using a chemical to do that job is a scale up of that argument to infinity because you aren’t simply turning off the tap of a hormone stream, you are adding a chemical with unknown other effects.

    I don’t know enough about the Zeuterin clinical trials or ancillary research, but I’ll take a flyer and say I doubt it would satisfy me. It seems like something is always overlooked in a push to market… toxicity in other body areas, unexpected cell signalling pathways, breed specific effects, etc etc..

  22. Thanks, M. Schlehr for your comments and questions. Zeuterin does not fully prevent formation of spermatozoa. What it does is create scar tissue that prevents spermatozoa from leaving the testicles. In this sense, it is somewhat akin to a vasectomy. Whether or not a Zeutered dog remains interested in breeding a female in heat is going to vary from dog to dog. As mentioned in my article, the behavioral ramifications of “half strength testosterone” have not been studied.

  23. As I understand it, Zeuterin prevents formation of spermatozoa, hence making the dog sterile. But, if testosterone is still produced, zeutering would not remove the urge to breed, to follow a bitch in season, etc, — or does it?

  24. Hi Peg. Thanks for your question. As mentioned in my article, there are no surgery or general anesthesia complications associated with Zeutering. In theory, Zeutering should cost less than surgical neutering. Lastly, I cited some research in my blog post that provide clear evidence that, at least for certain breeds of dogs, surgical neutering, particularly performed at a young age, creates a higher incidence of certain types of cancers, orthopedic issues, and behavioral problems.

  25. I will neuter my next male puppy w/ Zeuterin. I have several clients who have done it already. The dogs did have pain afterwards, minimal but it’s not pain free. They are doing well and socially don’t have any issues w/ other dogs, even other males.

    I’m thrilled that we have this alternative.