Dog Health, Responsible Breeding

Esterilsol and Neutersol – chemical neuter of dogs

One of the things I’ve been watching relatively closely, as a breeder, is the availability of nonsurgical neuter methods.

A few years ago a company got FDA approval for, and marketed, a product called Neutersol, which was a simple injection of zinc gluconate into each testicle. Zinc gluconate is caustic to tissue and kills the sperm-producing cells.

It was incredibly safe and effective, but died quickly and was withdrawn from the market. Why? Because somebody decided that it was a goose that would lay a golden egg, and they priced it so high that it was comparable to surgical neuter. No vets would buy it, and very few owners wanted it. It seemed ridiculous (and I agree) to pay that much for an injection.

Also killing the sales was the fact that the injection left the dog with a lot of testosterone production, though he couldn’t produce sperm. So it didn’t produce quite the same effect as early physical neuter – the dog would still have some interest in female dogs. And – and apologies to those who are now going to close their eyes and grimace – it didn’t produce the same cosmetic effect. Most pet owners think that the neutered penis – which is very, very small – is a “normal” one, and that an unneutered one is big, gross, and ugly. Neutersol allowed the dog to grow a normal-sized one.

A very small number of dogs got what looked like infections or injuries from the neuter, which nobody could figure out.

The final nail in the coffin was that the injection was approved only for puppies, from three to ten months old. That was too small a window for most vets to feel it was worth it.

(As a very interesting aside, my sister’s dog Wilson was – I don’t even know what to use as a verb… unmanly-manned? – with neutersol, which means his age, which was a mystery when she got him, was able to be rather precisely dated because Neutersol was on the market for such a short time and was only used in puppies.)

Over the last few years, however, with the explosion of dog sport, there’s a much larger demand for a neuter-that’s-not-a-neuter. People who work their dogs want the protection that testosterone provides. And breeders often prefer to keep the testosterone flowing as well; testosterone closes the growth plates and intact dogs are typically shorter, wider, and sturdier than neutered ones, and their muscle tone and tendon strength are better.

Vets and NGOs in developing countries were also dismayed to see Neutersol go, because they had this “It was almost great!” feeling about it. An injectable neuter is pretty much the holy grail.

And so, with support from a whole set of places, a few organizations continued to work with the compound-that-had-been-Neutersol (it’s not exactly hard to put your hands on). They wanted to solve the big issues with it and push it into wider production again. They’ve now (sort of) done that, and their version of the same injection – tradenamed Esterilsol – is now available everywhere BUT the US.

Surprisingly, the way they solved the problems with Neutersol was not by changing anything about it. They just changed the way it was used. They figured they had nothing to lose by giving it to a bunch of older dogs, so they did, and lo and behold it works beautifully on dogs of any age. As an added benefit in developing countries, there are much smaller changes in cosmetics, so the dog doesn’t look neutered. They’ll even breed with females, though their libido is reduced. They just can’t produce puppies.

They eliminated the cost issue by actually charging what it was worth, which ends up being about $4.

And they realized that the infections were caused by the zinc getting on the skin and badly irritating it, which made the dog lick and bite it, which caused all kinds of problems. They were able to pretty much eliminate the problem by simply changing needles before the injection; it’s drawn from the bottle with one needle and then the needle is changed, so it’s clean and doesn’t leave any zinc on the skin.

With those changes, it becomes a solution that’s actually viable, and I am hoping like crazy it will come back to the US as well. It’s something I’d be MUCH happer with owners taking advantage of than a surgical neuter, because the continued production of testosterone is so protective and because it avoids the need for anesthesia, which has always been the biggest risk of any conventional neuter.

Now if only they’d invent an injectable debarker…

On the home front: Still waiting on Clue. She’s doing the same annoying slow-to-get-going thing she did in her last heat, so (unlike the last time) I am relaxing and letting her tell me when things are starting to chug along. She may decide to ovulate on day 17 again, so we could be into September before anything exciting happens.

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  • Reply Raegan August 18, 2010 at 1:27 pm

    I’m curious as to why dogs that don’t look neutered is a benefit in developing countries? I would think that the benefit of a visible neuter is that it is visible. What happens if the dog is later castrated? I could see a dog going into a shelter, picked up as a stray or whatever, and the shelter director taking one look at him and saying “Well those have got to go.”

    • Reply Christine August 18, 2010 at 7:49 pm

      Raegan — I would think the most significant benefit would be the low cost–$4 versus $200–and the elimination of health risks from surgery (anesthesia, infection, recovery, etc.). I would think the speed and cost would be invaluable to shelters all over the world. Additionally, I understand one of the big obstacles to neutering in many 3rd world countries (in addition to the cost) is that it’s not “macho” (same reason many men in the US don’t want their dog neutered).

      For Joanne–is there any way to know if a dog was treated with Esterilsol? For instance, say you’re buying a stud dog for breeding –is there any way to know he wasn’t sterilized? (It would take some seriously dubious behavior for this to happen, but it would be good to know.) Alternatively, say you adopted a dog you found on the street–would you have a way of knowing he’d been injected or would you just inject again?

      • Reply rufflyspeaking August 18, 2010 at 8:52 pm

        I think a tattoo scheme would have to be worked out. You could do a quick “x” or similar near the scrotum without putting the dog under.

      • Reply rufflyspeaking August 18, 2010 at 8:58 pm

        My sister’s dog who had it done as a puppy has two intact, normal-feeling testicles – just very small. I would guess it arrested them in whatever size they were when he was done. They’re maybe a little soft, but I can’t even say that for sure because puppy testes are softer than adult. I think the only way to do it reliably would be to have a tattoo signal that’s as universally recognized as an ear tip for a feral cat.

  • Reply Ann August 18, 2010 at 1:48 pm

    I read the “smaller changes in cosmetics” to mean “people in developing countries are used to how un-neutered dogs look so it doesn’t bother them the way the average US pet owner might be bothered”. Seems like this would be a great boon if it got re-introduced to the US but I agree that the inability to look at a dog and tell if it has been neutered might be an issue.

    • Reply Kamie August 18, 2010 at 2:47 pm

      I think that could easily be solved with a small tattoo. I really think more vets should do this. It is a pain to pull a dog from a shelter, open her up and find out she is spayed.

      • Reply Erin August 18, 2010 at 4:01 pm

        That is a great idea! Actually my female was tattooed when she was spayed (if you think about it, same issue as a non-surgical neuter, you can’t tell by looking).

      • Reply Brianna August 18, 2010 at 8:27 pm

        This would have happened to our rescue had she not been found with what they think was her sister. The vet shaved their bellies and noticed identical lines that lead her to believe they had both already been spayed. If found separately they both would have gone through an unnecessary surgery.

  • Reply Erin August 18, 2010 at 2:46 pm

    To me, the risk of not being able to tell if a dog in rescue is neutered or not is a small issue when compared to the health risks of early neuter. I love that there could be a way to stop sperm production without stopping the testosterone in the body. Would there still be some “inconveniences” that we as a nation of castrated dogs might have to learn to cope with? Yes, but I also think fewer dogs would have the kinds of injuries that come from stopping hormone production way too young. Not to mention the funny, skinny, long-legged look you get from young castration. I am all about this! I hope it does come back to the states, and I will be the first person to recommend it to my male puppy owners.

    Joanna, is there any thought that there might be something similar for females to stop ovulation? I know women can get birth control shots to stop ovulation, but obviously estrogen continues to produce. If you did that though would you still have the issues of pyo and such, meaning that pet females would still be safer off with a hysterectomy?

    • Reply micaela August 18, 2010 at 3:39 pm

      I have the same questions as Erin and the others, and also: what about cats?

      Funny thing, my EllieMae and her littermate/brother were altered after they were a year old, and both are super-sized versions of their breed — Ellie’s 70lbs, Dadgum is 80+, both of them lean & tall. It struck me to read that intact dogs are typically shorter and wider…

    • Reply rufflyspeaking August 18, 2010 at 9:03 pm

      Yes, there are approaches for girls but they’re at an earlier stage of research.

      You can stop ovulation in bitches short-term very easily. You can’t stop them permanently right now. The two things I’m aware of being in testing are a one-year/three-year implant (one year for female dogs; three for female cats, which may end up finding a greater market among show/working people than among rescue groups and NGOs (nobody wants to round up the entire feral cat population more than once in their lives!) and a couple of chemical approaches that try to kill the ovary follicles. Neither one is – as far as I know – close to release.

  • Reply Pai August 18, 2010 at 6:32 pm

    This is a great thing, in my opinion. After learning a lot about the topic of hormones and growth and side effects of S/N over the past few years, I will always be more hesitant to neuter any male dogs I own in the future.

    And if I get any coated breeds… I may even opt to leave the females intact too, since I’ve heard that spaying can change the texture/amount of their hair for the worse, too.

    • Reply rufflyspeaking August 18, 2010 at 8:55 pm

      Spaying DOES change hair. The “spay coat” is well known. However, since leaving them intact puts them at high risk of pyo, I don’t think it’s worth it just for the coat. Doesn’t mean I like the coat changes, but I will spay a retired bitch as a default, whereas I’d have no such conviction about a boy.

  • Reply Katie August 19, 2010 at 1:17 am

    I would absolutely consider that option for a future dog if it becomes available. Although the reasons I was pushed to have my puppy neutered young (I didn’t do him until he was 18 months) had nothing to do with fertility and everything to do with testosterone poisoning (aggression, roaming, marking, all those “bad dog” things that neutering somehow magically cures, and which weren’t an issue in the first place).

  • Reply Karen@ACC&D October 9, 2010 at 2:47 am

    Our organization, the Alliance for Contraception in Cats & Dogs, is quite familiar with Neutersol/EsterilSol. Answers to many of these questions about this technology can be found at

    The company that’s behind EsterilSol reports that they are taking steps to reintroduce Neutersol in the U.S., so in the next several years, an alternative to castration may well be available here again!

    • Reply rufflyspeaking October 9, 2010 at 2:58 am

      That would be very good news indeed!

  • Reply Rachel December 3, 2010 at 8:11 pm

    I Show Dogs and I also breed… I back this fully heartily … It enables me to keep dogs I want to show but may never breed it also allows me to let the Puppies be fix that are going to pet home before they leave and they can get the full benefit of the hormones that are important for their growth and health… I cant wait until this comes back to the USA…. We really need this back here…..

  • Reply Jennie Davies April 23, 2011 at 10:02 pm

    I live in Northern Canada, where dog overpopulation is a HUGE problem. Chemical neuter would alleviate so much suffering. I wish it reduced testosterone too though… the dog fights when a bitch is in heat are brutal.

  • Reply Jean July 6, 2011 at 2:20 pm

    “Katie on August 19, 2010 at 1:17 am said:
    I would absolutely consider that option for a future dog if it becomes available. Although the reasons I was pushed to have my puppy neutered young (I didn’t do him until he was 18 months) had nothing to do with fertility and everything to do with testosterone poisoning (aggression, roaming, marking, all those “bad dog” things that neutering somehow magically cures, and which weren’t an issue in the first place).” There is no such thing as testosterone poisoning. Neutering does NOT magically cure the issues mentionned, good dog ownership which includes training cures them, or manages them. I suspect Katie is speaking tongue in cheek but it is not clear from her post if she is or not, hence my reply to clear it up, in case an uneducated reader might take it the wrong way.

  • Reply Sandeep Manchanda August 16, 2011 at 10:54 pm

    Esterilsol is expected to start shipping in the US first quarter 2012.

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