Chemical Castration : The Future?

I’m going to tackle the article sent in my by one of my regular readers. It’s an interesting article. In case you missed the link last Thursday, here it is again:

New Strides in Spaying and Neutering

The short version of the story here is that there is a company relaunching a product and method to “neuter” a dog by giving an injection in the testicles. It prevents reproduction but does not fully eliminate testosterone production.

There’s some history here. The original company that produced this formula (Neutersol) launched their product in 2003. There were issues with ownership and production that led to the discontinuation of the product. Another company, Ark Sciences, bought the rights and is relaunching the same product under the name Zeuterin.

Simply put, a dog is given an injection of a zinc-containing compound in the testicle. It causes inflammation that destroys the sperm-producing cells, which causes the dog to be sterile. In comparison to a regular castration, the testicles are NOT removed after injection. They do sometimes decrease in size, but it’s my understanding that that effect varies.

I have not yet been through the training that Ark Sciences is requiring to use Zeuterin. It’s my understanding that with the prior company/product, the dogs didn’t require much in the way of sedation, and they generally didn’t require full anesthesia. If I recall correctly, the post-injection care was pretty minimal. Some dogs were quite painful after the injections. That should be something fairly easy to address, however. Sometimes the testicles swell after injection, which is to be expected. This, too, causes pain; again, it shouldn’t be hard to address. As far as I know, there don’t seem to be any longterm problems with this method of sterilization.

So, why the fuss? Why is this news fit for a headline? Lots and lots of reasons. Neutering is a long-running debate with decades of vehement support on both sides. The US is a country in which neutering dogs at a young age (less than 1 year) is most commonly recommended. In other parts of the world, neutering is NOT recommended at all. There are pros and cons as well as many unfounded fears circulating on the internet. Inaccuracy and belief-over-evidence runs rampant, too.

Here’s what I know for sure about surgical castration:

  • Castration reduces the risk of perianal tumors (usually benign tumors around the anus of intact male dogs).
  • Castration eliminates the risk of testicular cancer.
  • Castration eliminates the risk of benign prostate enlargement.
  • Castration reduces roaming behavior and dog-dog aggression in most male dogs.
  • Castration addresses overpopulation of stray/feral/ dogs.
  • Castration of very young male dogs can alter their physical appearance slightly; the medical significance of this is less certain.

There are valid questions out there about the risks of castration, particularly early in life. Early neuter may well cause increased risk of some medical problems, including cancer, abnormal bone growth, and possibly an association with mental decline later in life. A higher rate of fearful behaviors has also been noticed in neutered dogs. Many of these questions require more study. It is, however, a very real possibility that neutering (and spaying) can cause some diseases to occur more frequently. What remains uncertain is whether the studies already published are as good as the results seem to imply. Interpreting historical data is much more complex and difficult than it seems.

I encounter a lot of fear on the part of clients about neutering. Many owners believe it will make their male dogs fat and lazy. They worry about the risks of anesthesia. They worry about the cost of the procedure. Sometimes, cultural beliefs make castration extremely unappealing as an option.

In many cases, these fears are easy to dispel. In my experience, neutered dogs are NOT less active or driven than their intact counterparts. Neutered animals don’t need as many calories as an intact male, so they will probably need less food. Overfeeding makes dogs fat, in my opinion, and is a much more potent factor than the presence of testosterone. (I’m not saying there’s zero influence of sex hormones on physique and body condition score. I’m saying most of my clients overfeed their pets.) Anesthesia performed properly is NOT high-risk. Yes, the procedure is costly compared to general well-health veterinary care. Discussing that will require a whole separate post, but I’m open to doing so in the future.

So what are we going to do with all of this information? I try to be practical about it. Honest, too, as there are some issues we need to confront head-on.

How many of these “benefits of neutering” can be replaced with deeply responsible pet ownership? Lots of them. Roaming behavior, inter-dog aggression, pet overpopulation… owners that were more hands-on with their dogs and willing to curb these kind of issues would take these problems off the surgical table and put them on the end of the leash. I’m not trying to be condescending or elitist. The flat truth is that if your dog is intact and you let him out in the backyard without a fence and with no supervision, you’re contributing to the problems. Pet overpopulation is a very real, very serious problem in this country. Not because roving packs of wild dogs are stealing children away, but because MILLIONS of stray dogs and cats are killed every year. Three to four million, in fact. Irresponsible ownership is a big part of that death toll.

Speaking from my personal standpoint, if an owner is responsible, I don’t see a problem with not neutering. Part of that responsibility is shared between the owner and the vet. I’m responsible for informing that owner of the risks and benefits of neutering. I’m responsible for answering honest questions with honest answers. Some of those answers may be, “We don’t know” or “Yes, there are specific diseases for which neutering raises the risk.” Together, owner and vet will have to weigh those pros and cons and select an outcome that works best for that situation.

In my experience, neutering is still the best case scenario for most male dogs and their owners. Our hospital still officially recommends neutering at 6 months of age.

This brings us neatly around to the actual topic of the original article. Can chemical castration replace surgical castration? I don’t think so. Not broadly, anyway. Chemical castration leaves some testosterone intact, and that hormone is the balance point for behavior and medical risk.

If a given owner is responsible and simply wants to eliminate the risk of unwanted puppies, then chemical castration is a very viable option. Remember that the presence of testosterone may also protect dogs from some of the diseases we mentioned above that occur more frequently in neutered dogs.

If the testosterone-driven behavior of a male dog will increase his risk of trauma, or increase risk to the family, other pets, other families, etc., then chemical castration won’t change that behavior. Surgical is the only way to go, as that’s the only way to eliminate the production of testosterone.

In summary, chemical castration isn’t a miracle cure for all of the controversy of neutering. I think it has a place in the discussion, as well as a place in the set of tools we use to keep pets healthy and safe. I would caution my clients and readers against thinking that chemical castration is “better” than surgical methods. It’s simply a different path to take as we navigate health care for our pets.

This is a broad topic. It was also a really long post. If you’ve made it this far, I thank you. If you’re hungry for more, check out this blog post: The SkeptVet

I’m happy to tackle questions, too. Comments welcome!



Filed under medicine, practice

2 responses to “Chemical Castration : The Future?

  1. Chris Miner

    Fascinating post. I know there are a host of diseases that neutered dogs won’t get, but I didn’t know there are diseases for which neutered dogs are more susceptible. It’s a tricky balance; isn’t it?

    I also didn’t know that this is a second go-around for the same sterilization drug. I had wondered about the testosterone effect that would remain after the fact, and you did a great job of explaining both sides to that.

    I consider myself to be a responsible dog owner. However, it’s an imperfect world, and there is always the unexpected. As you pointed out, there are millions of dogs and cats that die every year for want of a loving family. In the end, I believe in neutering. As always, I would trust you to give me your best advice, and we would go from there 🙂

  2. I appreciate the trust. The article you sent was a great opener for a very broad discussion. I could have written twice as much! Thanks for the tip!
    With female dogs, I still advocate spaying before the first heat cycle. I think the benefits outweigh the risk. Males, though, that’s a whole new ballgame. I’m eager for more data to become available as time goes on. I think we’re going to see some pretty monumental shifts in how we practice over the next 5 years.