Calchlorin Male Sterilization

Calcium chloride in alcohol (“Calchlorin”) nonsurgical sterilant for male animals

What is it?

A low-cost nonsurgical neuter shot for male dogs, cats, and other animals. We’ve termed the mix “Calchlorin” for ease of reference, but it is not patented and is readily available to all. Coverage of Calchlorin in the Wall Street Journal. Not the same as Zeuterin(TM), a more hormone-sparing sterilization shot that is FDA-approved for dogs but, as of 2016, no longer available.


Available for use now, in the U.S. and every country with access to the two ingredients (calcium chloride dihydrate, and pharmaceutical-grade or food-grade pure ethyl alcohol). Can be ordered by veterinarians from a reputable compounding pharmacy (“20% (w/v) Calcium Chloride Dihydrate, USP in Ethyl Alcohol 190 proof, USP”), or from the Canadian supplier to veterinarians worldwide.

Where to start/how to use it

Watch the following introductory video to learn its history, then see for a step-by-step checklist and SpayFIRST! for up-to-date instructions video and important usage tips.

Nonsurgical sterilization for dogs and cats: Calcium chloride from Parsemus Foundation on Vimeo.

Nonsurgical sterilization for dogs and cats: Calcium chloride from Parsemus Foundation on Vimeo. Note on ending: We are no longer pursuing FDA approval; however, there is now, six years later, enough data in peer-reviewed publications (Jana 2011, Leoci 2014) and U.S. field use (over 1,000 dogs) to allow informed decisions about its immediate use.

Parsemus Foundation’s Role

Spreading the word, after having funded research (2014 Italian study) to improve the level of evidence so veterinarians and rescue groups can make a fully informed decision about whether it is appropriate in their context. Collecting data from early adopters to increase the level of evidence. (Using calcium chloride? Contact Us for information about data submission prizes.)

Stay informed

Get the latest information from and for early adopters! A Facebook page has been set up by a Canadian supplier of calcium chloride worldwide.


Use the checklist and step-by-step guide at to organize your efforts, with particular attention to the Spay First! materials and video.

Still hungry for more? Watch the first of two presentations on calcium chloride at the Alliance for Contraception in Cats & Dogs 5th International Symposium, June 2013:

Calcium chloride presentation at ACC&D 5th International Symposium, June 2013 from Parsemus Foundation on Vimeo.

Want even more background info? View second presentation “Could your organization use Calcium Chloride? Nuts and Bolts” below. Calcium chloride talk begins at 37:54. Part of the panel presentation “Getting involved in field testing of non-surgical sterilants: Lessons learned, and what organizations and veterinarians should consider when getting involved” at the Alliance for Contraception in Cats & Dogs 5th International Symposium on Non-Surgical Methods of Pet Population Control.

ACC&D Getting Involved in Field Testing Session from PCMA on Vimeo.

For tips on nonsurgical neuter in context and best practice, see the following video:

Animal Grantmakers 2014 Conference – Ruth Steinberger Spay/Neuter Presentation from Parsemus Foundation on Vimeo.

Advice from experienced users

Have you read everything, watched the videos, but want the reassurance of some firsthand advice from early adopters? If you have questions after reviewing all the material here, these experts who have been using Calchlorin have offered to share their experience and perspectives:

Ruth Steinberger
co-CEO, SpayFIRST!
ruth [at] spayfirst [dot] org
* experience using Calchlorin in the US

Heather Steyn, DVM
Owner, Advanced Animal Care of Colorado
1530 Riverside Avenue
Fort Collins, CO 80524
drsteyn [at] advancedanimalcareofcolorado [dot] com
* experience using Calchlorin in Ecuador

 Marcela Pineda, DVM
Director, Amici Cannis Ecuador
marceangeles22 [at] hotmail [dot] com
* experience using Calchlorin in Ecuador

Raffealla Leoci, DVM, PhD
Department of Emergency and Organs Transplantation
University of Bari Aldo Moro
Valenzano BA, Italy
leocivet [at] yahoo [dot] it
* researcher who determined optimal formula in studies in Italy

Kuladip Jana, PhD
Division of Molecular Medicine
Bose Institute, Centenary Campus, Kolkata India
kuladip [at] bic [dot] boseinst [dot] ernet [dot] in
*researcher who published groundbreaking papers on calcium chloride

Data downloads, instructions, and cautions

  • Published papers since 1977: Publications 1977-2010 are available on PubMed (often abstracts only) and listed/linked in this downloadable bibliography. The most recent papers (2011 Jana cats, done using older formulation; 2014 Leoci dogs) were supported by Parsemus Foundation and are available open access, full text, free online. Also available is an unpublished paper on the use of Calchlorin in adult male goats.
  • Regulatory resources: American Veterinary Medical Association policy on compounding: Overview; from bulk substances; and printable PDF. Review of other regulatory issues veterinarians should consider by country.
  • Important real-world usage tips: For definitive technique instructions, revised dosage for large dogs, refinements, and cautions based on experience in more than a thousand dogs, see SpayFIRST! online materials and video including potential complications. Must-read for effective use. For formulation tips for ultra-low-resource settings/countries without access to compounding pharmacies, see “Ingredients & Technique” document (but when in doubt or in case of any conflict between them, always defer to the instructions at SpayFIRST!).


An independent review of the data

The scientific advisory committee of the Alliance for Contraception in Cats & Dogs has produced an extensive independent review of the data through November 2014 (before publication of the Leoci 2014 dog results).

Background material

Given the lack of clear evidence for a population impact of sterilizing males, reducing unacceptable male behavior is the primary evidence-based reason welfare groups castrate male dogs and cats.  A sterilant which does not reduce male behavior can be useful in certain situations (such as working dogs), but cannot replace all shelter castration surgery; male cats in particular are considered unadoptable if their behavior is not altered.

In December 2009, Parsemus Foundation’s director got to witness a demonstration of an injectable sterilization for male dogs which knocks out most testosterone — and thus some spraying/marking, roaming, packing, and fighting, along with associated bites, disease transmission, and wounds.  It is backed by several decades of scientific papers (these can be found in the bibliography link above), most recently with a 2011 publication on use in cats from the Indian team (Jana/Samanta) and two 2014 publications on use in dogs (Leoci).

Dr Kuladip Jana

Dr. Kuladip Jana, one of calcium chloride’s two primary developers, with his poster presentation (data from the first large trial in cats) at the Alliance for Contraception in Cats & Dogs 4th International Symposium on Non-Surgical Methods of Pet Population Control in Dallas, Texas, April 2010

The approach was originally published in U.S. journals, but would then have been largely forgotten had it not been unflaggingly pursued by the team of Dr. P.K. Samanta and Dr. Kuladip Jana in India. Their work in cats was subsequently confirmed by a study in Turkey, presented as a poster by A. Baran at the 2010 Alliance for Contraception in Cats & Dogs Symposium on Non-Surgical Methods of Pet Population Control.

In February 2010, the foundation’s director went to India and filmed the procedure in action. The video above gives both a firsthand view and a perspective on its use.

Male castration surgery is much quicker and simpler than female spay.  So could a nonsurgical method really make a difference to shelter and rescue group budgets and effectiveness?  The short answer: Dramatically, yes.

Out of about 6 million neuter surgeries per year in the U.S., about 1 million are subsidized or “low-cost” neuter surgeries performed in shelters or by contracting veterinarians. Those neuter surgeries generally cost $35-$140 to the organization in supplies, anesthesia, and veterinarian time. For example, the “low-cost” clinic in our area (San Francisco Bay Area) charges $50 for male cats and $80-140 for dogs depending on weight; a clinic in a representative lower-cost area (SNAP in San Antonio, Texas) still charges $40 per cat and $50-90 per dog.  Materials cost for a dog neuter are generally $8-10, with the rest of the cost being labor. This injectable, however, has a materials cost of less than $1 per dose (including syringe) — less than the cost of one piece of suture.

Injectable neuter, then, can be offered for about the same cost as a rabies vaccination. SpayFIRST!, for example, estimates they can offer Calchlorin neuters for less than $3.50. Assuming an average $35 saving versus surgery (given that a few minutes of staff time are still involved for injection in addition to the materials cost), then U.S. shelters alone could save $3 million of hard-raised money each month through use of an injectable.

Zeuterin(TM) zinc gluconate injection (called “Esterilsol” when it was on the market in Latin America) came onto the U.S. market in February 2014, and if its about 40-50% average testosterone reduction had resulted in enough behavior change to meet shelters’ needs and its price had been ultra-low, then it could have filled this role; but Zeuterin is more hormone-preserving than behavior-changing and did not routinely replace shelter castrations before the company went bankrupt in 2015. In fact, it was Zeuterin/Esterilsol was specifically marketed as creating no significant behavior change (see graphic below). In any case, with Esterilsol/Zeuterin now off the market, rescue groups have no FDA-approved nonsurgical option of any type, hormone-sparing or neutering.

Esterilsol Chart

With the safety and efficacy of calcium chloride in dogs now shown in two publications from Italy, funders funding subsidized spay/neuter surgery (some up to $8 million per year) should be particularly interested in this opportunity to make their money go further.  The largest benefit comes if more males can be sterilized quickly and safely, leaving organizations more time and resources for sterilizing females and finally getting ahead of population. And internationally, an injectable may make male neuter an appealing option where transport to clinics puts street dogs under great stress and surgical neuter would not be economically or logistically feasible, especially as part of trap-neuter-vaccinate-release (TNVR) and rabies programs. Funders should help create a world of no more surgery for male dogs and cats, and make their support go further, by declaring that after a certain date, new spay/neuter grants will support only nonsurgical sterilization, not invasive surgery, leaving more funds for female spays.

Parsemus Foundation has helped the research team in India fund completion and publication of additional studies. The foundation has also funded a study of calcium chloride by an independent team at the veterinary university of Bari, Italy, comparing the mix used in India (calcium chloride in lidocaine base) with two other formulations, calcium chloride in saline base or pure alcohol base; the 1-year study results show calcium chloride in an alcohol base even more effective than in a lidocaine or saline base. The most effective formulation with the fewest side effects was determined to be 20% calcium chloride by weight in pure grain alcohol (e.g. 2 gr of calcium chloride powder in about 10 mL alcohol, filtered through a 2 micron filter or autoclaved, and sterile filled, enough to sterilize 5 dogs or 20 cats; or 20 grams of calcium chloride in about 100 mL alcohol to sterilize 50 dogs; details in downloadable documents above). Both research teams presented their results at the First International Conference on Dog Population Management at the Food and Environmental Research Agency in York, U.K. September 6, 2012 (see Book of Abstracts and presentation PDFs, session 8) and the Alliance for Contraception in Cats & Dogs 5th International Symposium June 2013 , and the university results from Italy were published in fall 2014.

What are the limitations of calcium chloride? A recent publication on the use of calcium chloride in donkeys is informative. Ibrahim and colleagues (2016) reported that calcium chloride was not effective in reducing testosterone in adult donkeys. Because the solution is not uniformly dispersed in large testes, calcium chloride does not seem ideal in larger animals such as donkeys. The same is likely to be true of horses, although future studies could investigate the multi-point injection technique successfully used in the 1970’s, or the addition of DMSO to increase dispersion. Recent unpublished work in adult goats also reflects the challenges of testicular sterilization in larger animals with a single injection. Until early adopters report on experimenting with multi-point injection technique in large animals, calcium chloride seems best adapted to animals with testes 2.4 cm in diameter or smaller.

So calcium chloride works. But when liability avoidance comes from doing the same thing as everyone else, even if there’s a better, faster, cheaper, safer way, which veterinarians will be brave enough to risk trying something new? The first U.S. veterinarians and shelters to try calcium chloride in dogs have now stepped up, with successful use in over 1,000 dogs, and discovered important information about dosing in large dogs (larger dogs than studied in India or Italy). Their experience and perspective were profiled with a story and video in the Wall Street Journal, and their important practical tips are a must-read for safe and effective use (links above).

Who will be next, beyond the handful of early adopters already using it? Uptake will require veterinarians and organizations secure enough in their mission, and that the welfare of the animals overrides all, to be willing to try something new.

Wondering whether calcium chloride could help get ahead of pet overpopulation and reduce euthanasia in your context? Your first steps: Read this page; watch the video and read the practical tips at SpayFIRST!; and then read the documents downloadable above before diving into the published literature (or asking your organization’s veterinarian to do so). You can organize your efforts using the step-by-step guide at

Interested in sterilization while preserving hormones?

Parsemus Foundation is also interested in furthering research on epididymal injection of Calchlorin (vs. testicular injection) for hormone-preserving sterilization — useful for health reasons in large dogs, and also as a nonsurgical alternative to vasectomy in both humans and animals. Testicular injection of Calchlorin is for nonsurgical neuter (eliminating or greatly reducing hormones). But — injected into the epididymis instead of testes, could Calchlorin sterilize while preserving testosterone production, providing an ultra-low-cost nonsurgical alternative to invasive surgical vasectomy?

Pilot studies from the U.S. in the 1970’s, and studies of other sterilants and in other species, indicate yes. Immature sperm leave the testes and travel to the epididymis where they mature and are stored until needed. Injection of calcium chloride into the epididymis can stop sperm transit without affecting the production of testosterone (which is made in the Leydig cells in the testes).

Parsemus Foundation is offering a small publication prize for open-access publication of research exploring this approach as a vasectomy alternative; please contact us (use form on Contact page) for details. For further information on hormone-preserving options (including epididymal injection and vasectomy), see our hormone-sparing male sterilization page.

Help calcium chloride make a difference

Parsemus Foundation has been spreading the word about calcium chloride sterilization, and supporting the work of researchers in India and Italy, for 6 years now. If you appreciate what we’ve done for animals, the biggest thanks (unless you have a spare million dollars to send our way, of course!) would be to pass the information on to your local shelter and rescue organizations and ask them to look into it! It shouldn’t take another 37 years to create a world of no more surgery for male dogs!