Chemical sterilization: A safe alternative for dogs?

Raffaella Leoci
Raffaella Leoci

Could chemical sterilization be an affordable solution to keeping stray dog populations under control? Raffaella Leoci, DVM, PhD, is a researcher at the University Bari Aldo Moro in Italy and a specialist in pet reproduction. She is the lead author of two articles published in Acta Veterinaria Scandinavica on chemical sterilization of dogs using calcium chloride, which identified the most effective concentration and the optimal solution. In this guest post she tells us why she thinks use of calcium chloride sterilization could be the answer to stray overpopulation.


Pet overpopulation is a serious problem across much of the world. In some regions such as where I live, the number of stray dogs is not under control and many dogs are killed by car accidents or suffer from serious illnesses.


Italian law includes a no kill policy and stray dogs are captured, microchipped, neutered and taken to dog shelters where they live the rest of their lives. Some are released because of overcrowded shelters. Unfortunately, the existing trap/neuter programs are unsuccessful and the dog population continues to grow.


These are grave issues with serious health and welfare implications for both humans and dogs. Surgical castration is not a solution: it is too expensive and time consuming. My priority was to find an alternative method that was safe, effective, inexpensive and easy to perform to prevent canine reproduction – and also prevent the suffering that dogs experience from life as a stray.


I have been studying various methods of nonsurgical sterilization since 2007, including ultrasound. Several years ago, I partnered with Parsemus Foundation – a U.S. based nonprofit organization with an interest in nonsurgical methods – to investigate the use of calcium chloride dihydrate (CaCl2) as a chemical castrating agent. CaCl2 is a commonly available salt used for various medical applications.


strays-504794_1920The first published reports of using CaCl2 to sterilize animals date back to 1977 and 1978 with the work of L.M. Koger and researchers at Washington State University, Pullman. But the procedure was neglected for decades until researchers Kuladip Jana and P.K. Samanta in India began exploring its use in companion animals. Their research provided good indications that calcium chloride could indeed be an ideal chemical sterilizing agent. Their short term studies in dogs and cats have been published over the past decade.


But more information was needed to clarify whether CaCl2 could be used on a wide scale as a nonsurgical sterilant. What is the best concentration and solution? What were the long-term effects? We also needed to better understand the safety and welfare implications and the impact on canine behavior. Our research projects were the first to study large numbers of dogs over a long time period (12 months) and evaluate different solutions of CaCl2 in an attempt to find the optimal solution.


We found that a 20% concentration of CaCl2 in an alcohol solution (called “Calchlorin”) met all our requirements – azoospermia over the 12 month study and a significant drop in testosterone and associated sex-linked aggressive and mating behavior.


The procedure was also safe, quick and easy to administer. The dogs even showed little reaction to the intratesticular injection. This makes sense since afferent nerve endings are located on the skin and capsule of the testis. There may be slight pain sensation when the needle pierces the skin, but the dogs are unlikely to experience pain from within the testis.


Though basic attention needs to be given to proper technique, the procedure, if correctly performed, requires no medical recovery and carries no risk of secondary infections – providing a great improvement over the welfare implications of surgical castration.


The use of CaCl2 could be particularly important for large scale canine neutering programs. In many developing countries or resource-limited areas, mass sterilization programs are often prohibitively expensive. An alternative method to surgical sterilization that is effective, easy to administer, safe, and affordable would offer immense benefits, allowing animal welfare organizations, public health programs, and governments to reach further with limited resources. Our research supports the use of CaCl2 as an excellent alternative to surgical castration.


The next steps in evaluating the impact of CaCl2 sterilization is gathering data from the field to evaluate its performance in a variety of environmental conditions with varied practitioner skill levels, dog sizes and temperaments. I look forward to the use of CaCl2 sterilization to improve the health and welfare of stray dogs in my hometown and around the world.

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It is important to note here that the emphasis for use is on MASS sterilization projects, such as locations like the one mentioned, where there are vast numbers of stray or poorly claimed dogs and money is an issue. Northern North American Aboriginal people often live in areas where the only “sterilization” is death by rifle 1-2 times a year on village strays. There are countless other situations where this kind of sterilization is a huge opportunity for safe population control. However, other important points should be mentioned here: this is ONLY used in MALE dogs, never females, as it it injected directly into the testicles. It is not normally or safely used for cats (at present.) It does NOT remove all testosterone effects, but usually helps to decrease them. It MUST be administered by a skilled and well trained person; infection, pain, and failure are common when that criteria is not met. Some dogs will eventually become fertile again with time (not a guarantee of lifelong sterility, but most of these dogs do not live long lives, and ANY decrease in fertility is a GOOD thing,) and you cannot tell by just looking at a male if the procedure has been done unless a tattoo or other marker is obvious. For all these reasons, it is not really widely recommended for individual pets, and the cost in the US to have it done privately is almost or exactly the same as surgical castration, for a variety of real reasons, so do not expect it to replace surgical castration here overnight. It is a good step forward for population control, as long as the safety and parameters are understood.

Linda Brent

Catadvocat – you are confusing calcium chloride sterilization with Zeuterin, which is a zinc gluconate mix that is on the market in some countries. Unlike Zeuterin, calcium chloride DOES have a significant effect on testosterone (reducing to barely noticeable levels and measurably reducing problem behaviors), is permanent and has been tested in cats. Also, it is pretty obvious if a male has had calcium chloride chemical sterilization – the testicles shrink up quite a bit and certainly more than Zeuterin. Hope this helps to clarify the differences. Similar method – totally different results.

Ruth Steinberger

We have now used this compound at spay/neuter programs at five tribal nations; it is a fantastic tool for saving time and money and thereby increasing the services. Thank you so much Dr Leoci.

Sure It Is

Have there been any long term clinical trials or is this only field
Testing, with only visual or reproductive indices recorded? ie no hormonal blood work etc.
How many dogs to date, side effects recorded, etc.


There are some very serious adverse events in Lawton Oklahoma that have not been mentioned. This needs to be addressed, otherwise the data loses credibility.


It is not just field use, it is two published peer-reviewed studies as described in the article above, which build on several decades of published work from India and the U.S.; the link for the publication discussed in the article above is . My understanding is that the supposed side effects in Lawton were the result of a disgruntled employee and have been discredited by an investigation as being unrelated. However, this brings up a good point: Anybody who uses an innovative technique or advancement will be subjected to extra scrutiny, so users of calcium chloride should take great pains to start slowly, cautiously, and make sure they do so with the thought-leader support. If they do so, the potential benefits are enormous! For a checklist of suggested due diligence before using calcium chloride, see .


Why is there still such little progress regarding calcium chloride sterilization? Surgical sterilization is never going to solve the overpopulation of stray animals while calcium chloride potentially could, but it seems no one cares?


i care. I am an expat in Ecuador, and I am working to get this technique utilized here. Sharing this knowledge is invaluable to the unwanted dog and cat population. Part of my work includes knowing who and where calcium chloride neutering is used and where it is offered, if you know of any places that practice this technique, please share with me.

R.B.S. Tyagi

can any body inform about the use of calcium chloride for sterilization of stray dogs in India.


I did research work on a group of male dogs on sterilization using 20% calcium chloride in India. Though it was a short duration research, it showed some positive results like oligospermia, decreased level of testosterone, decrease in size of testicles etc. I faced little discouragement from some of my senior vets. Thanks to Leoci, Jana and Samanta, your work kept me motivated.

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