For decades, vets have been recommending that pet owners get their animals spayed or castrated. It’s a common topic brought up the first time we meet your new puppy or kitten. No doubt you are all familiar with the reasons why neutering is important; preventing pet overpopulation, unwanted pregnancies and certain diseases, among other benefits. There may of course be certain reasons why you choose not to get your pet neutered, which is fine.

However, today’s article will focus on owners who wish to get their pet neutered, but aren’t convinced by vets recommending a traditional surgery. With anywhere from 30-50% or more of UK dogs not being neutered, and probably even more cats, there are clearly a lot of you out there who might consider other options, such as a neutering implant, which is our topic for today.

Why Not Surgery?

As we mentioned above, surgeries to neuter your pets have many benefits. Aside from reducing the chance of unwanted pregnancy, it also has a number of health benefits. Neutered pets live longer, cannot get cancer in organs that are removed, may have improved behaviour, have no risk of false-pregnancy or pyometra and have a lower risk of some other cancers. Furthermore, these surgeries are quick, generally very safe, relatively easy to perform, permanent, and are often subsidised by practices to lower their cost.

However, there are a number of drawbacks as well. Certain breeds of dogs are at higher risks of other cancers post-neutering, have an increased risk of urinary issues, greater tendency for obesity, increased risk of orthopaedic diseases, and neutering can sometimes not fix or even worsen behavioural issues. Although the risks are low, surgery can cause bleeding, infection, failure to achieve the desired outcome, or other complications. Some of you may be worried about these side effects or complications. This is normal, we advise you discuss them with your vet to decide if surgery is right for your pet. 

Male Neutering Implant:

One of the more common alternatives to surgery is a neutering implant for male dogs and cats. This is a little cylinder, placed under the skin on the back of the neck, containing a drug called deslorelin. Deslorelin is analogous to a chemical in the body called GnRH. Small amounts of GnRH causes your pet’s testicles to produce sperm and testosterone, and make him fertile. However, larger amounts of GnRH have the opposite effect, shutting down the testicles and lowering fertility. 

How does it work?

The implant works by regularly releasing a large amount of deslorelin that causes the testicles to stop producing sperm and testosterone. The effects of the implant are the same as if your pet had been surgically castrated, though it takes about 6 weeks to take full effect. Depending on the size of the implant, it lasts for 6 or 12 months before it must be replaced. The previous implant is harmlessly absorbed by your pet’s body, so does not need to be removed. 

Why would you use it?

The implant may be a better choice than surgery for some owners, such as dogs with behavioural issues; the implant can offer a ‘try before you buy’ product to determine if permanent surgical castration would help improve their behaviour. The same is true for owners of working dogs who are worried that permanent surgery may affect their behaviour negatively. Although it can be useful for owners who may wish to breed from their pets in future. It should be noted that in some males fertility may be permanently reduced after the implant wears off; we thus do not recommend the implant if you ever wish to breed from your dog or cat.

As mentioned, surgeries always carry a small risk. So for pets that are old, immunocompromised, or have other reasons why surgery is too impractical, the implant may be a convenient alternative. The implant is small, painless and stress free, so owners of nervous pets may wish to consider it too. Although we would normally recommend castration as the treatment option, deslorelin has also sometimes been used to treat certain diseases caused by having too much testosterone, such as an enlarged prostate

What are the disadvantages?

Although the implant is temporary, some of these effects of fertility suppression may be temporary and disappear once the implant wears off. Others, though, may be permanent. There have not yet been studies investigating whether long-term implant use could lead to the same increased chance of certain cancers, obesity, and orthopaedic diseases as surgery. 

Other downsides of the implant include that it is slow to take effect. So male dogs or cats given the implant must be kept away from unneutered females for at least 6 weeks. Furthermore, once the implant wears off, fertility can return; so you should ensure that your pet’s implant is kept up to date, just like vaccines and flea treatments. Finally, consider that the implant is relatively new, compared to the tried and tested surgeries. Vets may therefore be less knowledgeable or less confident using the implant versus surgery. You should also consider that surgery is a one-time fee, whereas an implant must be regularly bought, so may be more expensive in the long run. Generally, if you are looking for long-term infertility, a one-time surgery is a better choice.

Female Implants and Other Options:

You may well be wondering if there is an implant for females as well, similar to the human contraceptive implant. As of writing, deslorelin is not licensed to be used in female dogs or cats to prevent pregnancy; however, studies have found that a deslorelin implant may shut down the female ovaries in a similar way to male testicles, and reduce fertility (although it does have a license for use in ferrets). 

There may also be another option for cats in the form of a melatonin hormone implant. This alters a female cat’s normal Spring-Summer breeding season. In future, both of these drugs may open the door for a licensed female implant, with all the benefits and drawbacks that it offers in males. Watch this space!


The other licensed chemical neutering option for females are drugs based on the hormone progesterone. Progesterone is released by a pregnant female to deactivate the ovaries and reduce fertility while her puppies or kittens (or baby) are growing. Synthetic versions of progesterone, called progestogens, work in the same way by tricking a non-pregnant pet’s body into thinking she is pregnant. While in this state, the ovaries shut down and the female cannot become pregnant if she accidentally mates. Females can be given an injection or tablet of progestogens at specific times during her cycle. This will postpone or even stop her heat, thus preventing a pregnancy. Though these drugs are generally reserved for short-term contraception, they have been used long-term to permanently postpone heat. 

Progestagens have similar benefits to the implant, but also carry a number of drawbacks. Long-term use is associated with diabetes, disorders of growth, local inflammation at the injection site, mammary gland enlargement, and even increase the chances of pyometra. Furthermore, as the reproductive organs are still intact, it is still possible for your pet to get diseases like reproductive cancers. The timings of the drug are very specific, and missing the window could mean your dog or cat is still fertile. Progestogens are good for short-term contraception but should be avoided for long-term chemical neutering.


Finally, for female dogs and cats who got a little too ‘friendly’ with the neighbourhood mutt or tom and accidentally got pregnant… There are various drugs can be given throughout pregnancy to terminate it. We do want to emphasise that terminations of pregnancies should only be utilised in an emergency. The prevention of pregnancy in the first place is always preferred. Pregnancies, even terminated, can be hard on a mother’s body, the drugs often have serious side effects, and terminating a pregnancy requires a lot of veterinary (thus financial) input. Furthermore, relying on termination of pregnancies means your dog or cat has no protection from the diseases and conditions we spay for. Generally, unless you are wanting to breed from your pet in future, a surgical spay is the best option for terminating a pregnancy. 

Final Thoughts:

We are increasingly recognising that castration or spaying is not the preferred choice for many pet owners. Therefore, it is important you know what alternatives we can offer – every pet is different, and surgery is not a ‘one size fits all’ option. Most vets would still recommend surgical neutering as the first choice in most pets. The safety, efficacy, speed and relative cost, as well as the long-term benefits must not be understated. We hope that today’s article has introduced you to alternative forms of neutering which you can discuss with your vet if you think they may be a better option for you and your pet.,9.4mg).