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Now cats, too: First US data shows nonsurgical dog neuter shot also effective in cats

First US results in cats win 'Timmy Prize' for data collection on calcium chloride nonsurgical neuter shot; the low-cost, universally available injection has the potential for significant impact on pet overpopulation worldwide

Parsemus Foundation


IMAGE: Timmy, the beloved dog of two donors who have sponsored the $5,000 "Timmy Prize " for data submission on Calchlorin nonsurgical dog and cat neuter shot. view more

Credit: R.Z. and S.B.

Old habits die hard. If veterinarians could sterilize male cats and dogs with a simple shot for less than a dollar a dose, why choose surgery? Well, now there's a choice--and some veterinarians, shelters, and rescue organizations are daring to try the new way.

"Timmy Prize" for data collection

A U.S. Northwest veterinarian and shelter have won the first "Timmy Prize" for data collection, submitting data on their experience using CalchlorinTM nonsurgical neuter injection to spare three feral cats surgery. The prize, offered by nonprofit Parsemus Foundation, is meant to encourage sharing and transparency of data on the neuter injection. Because the universally-available method is not patentable and there is very little profit potential, no company is sponsoring it or spreading data. "Market approaches can solve a lot, but in this case, we saw a need that wasn't being filled," said Elaine Lissner, executive director of the nonprofit foundation.

The prize is named in honor of Timmy, the beloved dog of two donors who sponsored the prize. "We read about Calchlorin in the Wall Street Journal last fall. It seemed crazy that this simple solution, which could spare dogs and cats surgery, wasn't being taken through the FDA by the big organizations. We wanted to at least help let people know it exists," said the donors, an international couple living in the U.S.

"When we adopted Timmy, nobody knew about Calchlorin--so of course we had him neutered the usual way," continued Timmy's owners. "But worldwide, not everybody can afford surgery. And given an option, I'm sure Timmy would have preferred a shot."

Worldwide dog overpopulation epidemic

Dog overpopulation is a problem globally, despite a range of efforts to control population growth. The American Society for the Prevention of Cruelty to Animals estimated that 3.9 million dogs enter shelters in the United States - only a fraction of the total number of homeless animals. In many developing countries, free-roaming dogs cause serious health and welfare problems that create socio-economic, ecological, political, and ethical dilemmas. Mass sterilization programs are often prohibitively expensive, especially in resource-restricted areas. 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.

Calchlorin sterilization, a potent solution

Calchlorin neuter shot, comprised of 20% calcium chloride dihydrate in ethyl alcohol, could be the answer--at least to half the problem. It eliminates the expense, surgical risk, and logistical challenges of doing surgery, at least on the males--allowing shelters and rescue organizations to concentrate scarce resources on sterilizing females. Although spaying female dogs makes the most difference for reducing population, male dogs must be sterilized too--in the case of street dogs, to reduce dangerous packing and fighting behavior, and in the case of pets, to reduce nuisance behaviors such as marking and mounting that end them back up in the shelter.

Neglected for decades

The use of chemical injections to castrate animals has been studied for over fifty years. While many chemicals are known to eliminate sperm when injected into the testicles, side effects were common. The qualities of calcium chloride as a safer chemical sterilant have been known since 1977 and 1978 publications by L.M. Koger and his team at Washington State University, Pullman. But the procedure was neglected for decades until Indian researchers Drs. Kuladip Jana and P.K. Samanta 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. However, this evidence did not result in broad adoption of the procedure, despite the potential positive impacts that a nonsurgical sterilization method could have on animal and human welfare.

Published studies from Italy

The results from two new studies have built on the research from India and clarified the optimal formulation for nonsurgical sterilization of male dogs. The scientific manuscripts, published last fall as open access articles in Acta Scandinavica Veterinaria, report that a 20% solution of calcium chloride dihydrate in alcohol ("Calchlorin") provides the optimal solution for safe and effective nonsurgical sterilization. A simple and quick intratesticular injection of Calchlorin caused infertility for 12 months and a reduction in testosterone with accompanying loss of male dog sexual behavior.

The research program, led by Dr. Raffaella Leoci of University Bari Aldo Moro in Italy, was the first to evaluate the long-term effects of the procedure on hormones, health and sperm characteristics in a large number of dogs. Dr. Leoci specializes in animal reproduction and is passionate about finding better sterilization options.

"Italian law has a no-kill policy, and stray dogs are captured, microchipped, neutered and taken to dog shelters - or just released when the shelters are too full. The trap/neuter programs are not on a large enough scale and the dog population is growing fast. This has led to serious health and welfare concerns," said Dr. Leoci. "Surgical castration is not a practicable solution- it is too expensive and time consuming. My priority was to find an alternative method to prevent dog reproduction that is safe, effective, low cost and easy to perform to prevent the suffering dogs experience as strays."

The initial study evaluated a number of concentrations of the chemical, and the second study evaluated the best diluent (solvent) to find a combination that is the most effective with fewest side effects. A 20% CaCl2 solution in alcohol (being called "CalchlorinTM") proved to be safe and effective over the 12 month trials. The procedure has the potential to revolutionize large scale dog sterilization programs, since it enhances welfare and reduces costs dramatically as compared to traditional surgical castration.

Psychological barriers

"For a long time, people, including vets, assumed that a testicular injection would be inhumane-- which is logical, since we all know getting bashed in the testes is excruciatingly painful," said Elaine Lissner, executive director of the nonprofit Parsemus Foundation, which sponsored the research. Lissner first read about calcium chloride in 2007 and, intrigued, requested a demonstration when she was in India in 2009. What she saw surprised her.

"I was amazed when I saw calcium chloride demonstrated in India that, though the dogs or cats sometimes yelped a little when the needle went through the skin just like for any other shot, they settled down once it was in. It's not what you'd expect at all."

Curious, Lissner asked expert veterinarian colleagues to explain. "It turns out that although there are nerves in the capsule of the testes that are exquisitely sensitive to pressure, there are not many pain nerves actually inside the testicular tissue. So as long as the injection is slow enough to not create pressure, it's amazingly well tolerated."

As a proponent of nonsurgical neuter methods and a scientific advisory board member of the Alliance for Contraception in Cats & Dogs, Lissner heard that practitioners wanted to see more data on the safety and long-term efficacy of using calcium chloride. Lissner allocated funds for the research led by Dr. Leoci to evaluate these concerns.

"Of course a nonsurgical sterilant for females is the holy grail from a population standpoint--and there's big money going towards that effort. But that's trickier. Now if rescue groups can at least get the males done quickly and easily so they can focus their resources on females, they have the first game-changing tool ever."

Behavior change is key

Preserving testosterone can be important for health reasons, particularly in large and giant-breed dogs. The FDA-approved sterilant ZeuterinTM is marketed as being more hormone-preserving and creating "no significant change in behavior." But for a sterilant to replace the great majority of castration surgeries in shelters and clinics, a reduction in testosterone-related dominance and sexual behavior is needed. "Pack behavior," including fighting over females in heat, is a prominent problem created by free-roaming dogs - and creates conflict with the human and animal populations nearby. And a pet dog that is mounting everything, breaking out regularly, or marking indoors is likely to end up back in the shelter--and possibly euthanized. Surgical castration greatly reduces these behaviors by removing the production of testosterone from the testes, making dogs more likely to keep their homes.

Dr. Leoci explains "As a rule, castration is most likely to be curative when the problem behavior is influenced by testosterone, such as scent marking, roaming away from home to find potential mates, inappropriate sexual behavior, aggression towards other males, and sometimes competitive aggression towards humans. It does not necessarily affect other behavior problems. In our study using the optimal solution of calcium chloride in alcohol, we did notice a reduction in testosterone-linked sexual and aggressive behavior."

Spraying, roaming, yowling: Changing behavior is key in cats, too

Reducing testosterone is especially critical when sterilizing cats. Unneutered male cats have extremely potent-smelling urine and are not adoptable as house pets. Yet surgically neutering large numbers of cats, especially transporting feral cats from the field, presents logistical problems. This makes the first U.S. data on cats, submitted by the winner of the Timmy Prize, particularly notable.

Published studies from India, conducted by Drs. Kuladip Jana and P.K. Samanta, already showed safety and short-term effect with an older formulation of calcium chloride. But the data submitted for the Timmy Prize was the first to try Calchlorin, the best-practices formulation as determined in the Italian dog studies, in cats.

The winning veterinarian and shelter made use of a little-known fact: cats have penile "spines" that are testosterone-dependent. By photographing the spines shrinking after Calchlorin injection, they were able to document testosterone reduction even without a blood draw.

Careful technique and practice important

The shelter veterinarian's experience also illustrated the primary caution regarding Calchlorin: although a surgeon's skill is not necessary, steady hands, careful technique, and a little practice are needed to have an optimal experience with the nonsurgical neuter shot. If the needle is withdrawn too quickly and there is some leakage, a scab can result. Indeed, this happened on one side on one of the first two cats.

"I knew when it happened. I made a note at the time of injection," said the veterinarian. "I withdrew the needle too quickly. In retrospect, it is good to know that you can sort of 'feel' if the injection didn't go well."

The cat recovered and the scab healed without incident.

Building on experience in dogs

The winning shelter is not the first in the U.S. to try the neuter shot. Spay FIRST!, the first U.S. nonprofit to adopt Calchlorin, tried calcium chloride nonsurgical neuter with great caution after hearing the results presented at the 1st International Conference on Dog Population Management in York, England. They started by replacing surgery in just three dogs. But when they saw how it went, they were "almost giddy" with excitement. "It's so much easier on the dogs than surgery," said Ruth Steinberger, Co-CEO. "We are able to use it in cold weather for many more dogs because there is little recovery time. A technician can inject under the supervision of a veterinarian so it saves professional time, shortening remote area clinics. And best of all, it works." Spay FIRST!'s experience was covered in print and video in the November 29, 2014 issue of the Wall Street Journal.

"Sweet spot": Small and medium dogs

In addition to submitting the first-in-U.S. cat data, the winning shelter presented data in 6 dogs of all sizes, from a Pomeranian mix to lab mixes to a 70-pound Rottweiler--a wider range of sizes than in the large published Italian study, which was conducted in mid-size dogs.

"All the dogs tolerated the injection well, and seemed bright and happy afterwards--it was definitely easier on them than surgery. But we didn't get the consistent testosterone reduction we hoped for in the big dogs. It would be interesting to know whether we're doing something differently than SpayFIRST!, and whether we could get more effect with a modified injection technique, perhaps withdrawing the needle slowly as we go like they did in the Indian studies. For us, smaller dogs definitely seemed like the sweet spot."

Hardest part: Explaining to other vets and the public

As in so many things, scientific change can come before societal change. The vets that have used Calchlorin so far find that the hardest part is not the injection, it's explaining it. "Having worked with this compound in a shelter scenario, it was hoped to save time and money and be a painless technique of non-surgical castration that could possibly avoid any surgical complication of licking and irritation," continues the winning veterinarian. "In my situation of rapid turnaround as to intakes and adoptions of the shelter environment, this type of sterilization must be explained to both the adopter and their veterinarian. The few vets that were recipients of such patients were less than receptive."

"I think a great use for this technique would be for spay/neuter clinics with very limited resources. The males could be chemically sterilized and the resources saved for the female surgical spays."

Indeed, after its experience using Calchlorin in chronic poverty was profiled in the Wall Street Journal, SpayFIRST! of Oklahoma received inquiries from all over the world, places where surgery is prohibitively expensive or impractical from a logistical standpoint. They are currently partnering with a Caribbean organization which wishes to introduce it to neuter strays. "The male dogs on the street are a real problem; but spending $35-200 per dog to neuter them is not even an option in these settings, when people can hardly feed their children," explains SpayFIRST!'s Steinberger. "So this is a real blessing."

Next steps

Shelters and rescue groups interested in using Calchlorin should read all background data and seek input from thought leaders in their community and the veterinary board in their country or state. The American Veterinary Medical Association maintains a state-by-state listing of relevant authorities.


More information about Calchlorin and the next round of the $5,000 "Timmy Prize" for data submission can be found at

About Parsemus Foundation: Parsemus Foundation works to advance innovative and neglected medical research. The foundation supports small proof-of-concept studies and then seeks to raise awareness of results, to ensure that they change treatment practice rather than disappear into the scientific literature. Many of the studies the foundation supports involve low-cost approaches that are not under patent, and thus unlikely to be pursued by pharmaceutical companies due to limited profit potential. More information on Parsemus Foundation and the work presented here can be found at:

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