Alternative to neutering

Updated April 17, 2017

According to the Humane Society, approximately three to four million dogs and are euthanized every year in the United States. Neutering and spaying are widely regarded as the best things the public can do to contribute to managing animal reproduction. However, alternatives are available to managing reproduction without surgically neutering or spaying animals.


Neutersol is a non-surgical alternative you can use to curtail fertility in your dog. Neutersol shrinks testicles and prostates in dogs between three to 10 months old. Contrasting with the traditional surgical castration method, Neutersol is a zinc and l-arginine-based compound injected into each testicle and causing permanent sterility.

Neutersol will not stop testosterone production in dogs. This means that dogs could still contract hormone-related diseases such as prostate disease or testicular cancer, as well as continue to exhibit behavioural characteristics such as marking, aggression and roaming, behaviours that are generally eliminated with surgical castration.

Side effects include testicle swelling within 24 hours of injection, diarrhoea, lethargy, vomiting and loss of appetite. This form of neutering is not available for cats.


Although not available in the United States yet, Suprelorin has been approved for use on dogs in Europe, and steps are being taken to enable it to be sold in the United States soon. Suprelorin is a contraceptive implant that halts testosterone and sperm products and makes the dog temporarily infertile. The drug binds to gonadotrophin-releasing hormones and overstimulates pets so they become desensitised to the hormone. Suprelorin becomes effective six weeks after initial implantation and remains effective for six months.

Suprelorin blocks testosterone, which can eliminate aggressive behaviour. Suprelorin can be reversed if you want to breed your pet at a later date. This product has not been tested on cats.

Megestrol Acetate and Mibolerone

Megestrol Acetate and Mibolerone are progesterone hormone drugs marketed to suppress oestrus, or "heat" in dogs. Megestrol Acetate is given orally to females during the fertile part of their menstrual cycle. It must be administered orally for eight days, then every four to six months. Mibolerone is approved only for up to two years of use and is given 30 days prior to the expected oestrus as a liquid added to food.

Some fairly severe side effects can ensue from both drugs, including increased appetite and weight gain, diabetes, depression, changes in temperament and hair loss. Both drugs are currently approved for dogs only.

Restrict Animal Access

A tried-and-true method of preventing unwanted litters is to simply avoid any and all contact between your animal and other animals. Particularly when in heat, dogs and cats are cleverer at escaping from the house or back yard, so it is a good idea to keep them locked up temporarily during this time. Dogs come into heat twice a year, while cats may come into heat at any time during the year. This method requires a very diligent and alert owner.

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