Pet overpopulation continues to be a public health problem in many parts of the world, with significant impacts on animal welfare. Surgical spay and neuter is the most common method to sterilize pets and reduce overpopulation, but can be challenging in low-resource areas. Inexpensive, non-surgical sterilization would fill a critical need. When used properly, a single intratesticular injection of a solution of calcium chloride dihydrate can chemically neuter male animals. It is inexpensive and effective, but requires proper technique and follow-up to avoid complications.
- Uncontrolled reproduction of dogs, cats, and other pets can lead to disease transmission to humans, suffering and early death of the animal, and environmental damage.
- More than half a million dogs are homeless worldwide. One female dog and her offspring can produce an estimated 67,000 puppies in just six years. Cats can produce five times that many!
- Surgical sterilization programs require financial and technical resources that are not available in all settings. Lifelong shelter housing and mass euthanasia programs are often used to control free-roaming pet populations.
- Surgical sterilization may not be practical or safe in all animals, especially small pets like rats and hamsters.
- Alternatives to surgical sterilization that are affordable and easy to administer can help reduce pet overpopulation and improve animal welfare even when resources are limited.
- A nonsurgical alternative may also appeal to dog owners who are averse to surgical castration, and be appropriate for pets that cannot undergo surgery.
- Nonsurgical pet sterilization methods have been targeted for research and development for decades, but few options are on the market. Newer developments in this field involve hormonal contraceptives, vaccines, recombinant viruses, and even gene transfer.
- Chemosterilization, which involves directly sterilizing an animal with a chemical, has been studied and used for 50+ years. A variety of chemicals have been injected into the testicular tissue to sterilize male animals. They work by simply killing the tissue, stopping the production of sperm, and rendering the animal sterile.
- Calcium chloride dihydrate is a chemosterilant that has been studied extensively in several species.
- The Parsemus Foundation has supported research and advocacy on calcium chloride to optimize the use of this sterilization method, with the goal of reducing pet overpopulation, eliminating the need for surgery, and improving animal welfare.
What is calcium chloride chemosterilant?
- A low-cost, nonsurgical neuter shot for male dogs, cats, and other animals. For an overview, see this coverage of calcium chloride sterilant in the Wall Street Journal.
- Made from calcium chloride dihydrate, a commonly available chemical that can be used as a chemosterilant when mixed into solution. Alcohol has been proven as a highly effective diluent for calcium chloride.
- Not patented, and thus available inexpensively 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 or can be prepared under sterile conditions.
- Most commonly injected into the testicles to result in sterilization with a significant testosterone drop. Can also be injected into the epididymis to sterilize without changing hormones.
For pet owners
The information on this website is for informational purposes only to promote broader understanding and knowledge of calcium chloride neuter. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your veterinarian.
Calcium chloride in alcohol has been used by a small number of veterinarians in various countries, most often for dogs. It is not in widespread use in the United States. If you are interested in calcium chloride as a sterilization option for your pet, check out our Veterinarian Directory, or discuss this option with your own veterinarian and provide links to the information on this site.
Checklist for veterinarians considering use
Keep in mind that successful use of calcium chloride sterilant is dependent on proper technique and follow-up. For best results, educate yourself on all aspects of its use, understand the potential for complications, and start slowly. Currently, this method is not suitable for large-scale neuter clinics or training sessions, or in settings that do not allow follow-up observations and treatment.
- Determine whether you are seeking hormone-preserving sterilization, or behavior-changing neuter. Calcium chloride sterilant reduces hormones similar to surgical castration (“neuter”), which is what most shelters and rescue groups are seeking. If hormone-sparing sterilization is desired, calcium chloride should be administered into the epididymis instead (see below), or another method (such as vasectomy) should be used.
- Read the instruction sheet and tips at SpayFIRST!, and watch the instructional video to determine whether calcium chloride could be similarly applicable in your situation.
- Read the peer-reviewed publication of dog study results from Italy and review the extensive bibliography.
- Watch the videos and absorb the background information on this website.
- Read the position statement and explore the resources and more conservative viewpoints at the Alliance for Contraception in Cats & Dogs.
- Decide on sourcing. Your options are ordering “20% (w/v) Calcium Chloride Dihydrate, USP in Ethyl Alcohol 190 proof, USP” from a trusted compounding pharmacy or obtaining and mixing ingredients individually (not advisable for veterinarians in countries with compounding pharmacies that provide quality control).
- Understand potential complications: Take a look at photos of possible complications that result if the chemosterilant escapes from the testicular capsule. Decide whether you are prepared for potential lesions (and prepared to explain them to clients) that resolve uneventfully if properly treated, but may occur especially during your learning curve. Calcium chloride injection is highly technique-dependent; the most experienced practitioners report complication rates less than 1 in 100, but new users may experience rates as high as 1 in 5 in dogs (complication rates appear to be much lower in cats and other smaller animals).
- Be able to conduct follow-ups. If a complication occurs, it needs to be addressed immediately so it does not become serious. Provide directions to owners on observing their pet and reporting any issues. Hold strays until you are sure there are no problems.
- START SLOWLY and PRACTICE. You can practice injections on ex-vivo testes obtained from traditional castrations to get a feel for the technique. Follow best practices, including informed consent, proper technique, systematic follow-up, and organized record-keeping.
- Before extensive use, explore the regulatory situation in your city/state/country, and seek input from local thought leaders and veterinary board/authority. The American Veterinary Medical Association maintains a state-by-state listing of veterinary authorities in the U.S.
- Veterinarians within an organization — present a plan to your organization’s board so the board can explore pros and cons and set policy with full board support. Your board may wish to seek legal input on issues around compounding and standard of practice if calcium chloride is not yet being used widely in your area. The Parsemus Foundation can provide resources and links.
- Private veterinarians — consider teaming with a municipal program to gain experience, avoid undue personal exposure, and assure full community buy-in.
Sterilizing dogs while preserving testosterone
Testicular injection of calcium chloride is for nonsurgical neuter (eliminating or greatly reducing hormones). But when injected into the epididymis, it sterilizes while preserving testosterone production, providing an ultra-low-cost nonsurgical alternative to vasectomy.
Injection of calcium chloride into the epididymis can stop sperm maturation and transit without affecting the production of testosterone (which is made in the Leydig cells in the testes). A recent study by Leoci and colleagues confirms that sterility can be achieved with an intra-epididymal injection of calcium chloride in dogs, with no drop in serum testosterone. However, the procedure required ultrasound guidance and takes as long as castration. Intraepididymal use of calcium chloride may be best for dogs whose owners do not wish to have any change in behavior or anatomy.
For surgical sterilization options, see our page on hormone-sparing sterilization.
For “pocket pets”
Calcium chloride may be especially suited to use in small mammals, including “pocket pets” such as guinea pigs, rats, rabbits, and hamsters. These pets often reproduce quickly, and owners need to keep them segregated by sex or have them neutered if they do not want offspring. Surgically neutering a small pet may be cost-prohibitive to some owners, and the risk of anesthesia may also be a concern.
Calcium chloride has been used experimentally in rats with good success (see bibliography). However, a study in guinea pigs did not find that animals were sterile following intratesticular injection of CaCl2, which may be related to species or method differences.
Procedures for sterilizing rats using calcium chloride
Most of the research using calcium chloride solutions for nonsurgical sterilization of small animals was conducted in rats. Here are some methods that were successful:
- Preparation — A 20% CaCl solution (or 10-20 mg CaCl2 per 100 g body weight) was found to be effective. Studies have successfully used saline, DMSO, or alcohol solutions.
- Sedation — Light sedation is required to prevent movement of the animal during the injection.
- Injection method — Jana (2006) positioned the needle along the codoventral aspect of each testicle approximately 0.5 cm from the epididymal tail toward the dorsocranial aspect. The solution was slowly and carefully deposited while the needle was withdrawn with care to prevent seepage of the solution from the injection site. Similar methods have been used by other investigators.
- Follow-up — The testicles will swell following injection and then shrink slowly over time to small remnants. Regular monitoring is important to identify any complications, and follow-up treatment may be required. Although uncommon in animals with small testicles, any leakage of the CaCl2 solution will cause necrosis of tissue and can result in a dry abscess.
- Effectiveness — Jana (2006) noted that rats receiving 5, 10, or 20 mg/100 g body weight were not fertile when placed with females at 21 days post-injection. Paranzini (2019) reported that rats paired with females at 100 days were not fertile after injection of 20% CaCl2 in 0.5% DMSO.
- Review the material here, including the publications and videos, before attempting to use calcium chloride as a nonsurgical chemosterilant. Since leakage of the solution can cause complications, consider practicing injections first to gain expertise with this material.
- If you use calcium chloride for pet sterilization, please consider adding your clinic to our Veterinary Directory so that others can find you.
- If you are looking for a veterinarian who offers calcium chloride nonsurgical sterilization for your pet, check our Veterinary Directory or talk to your own veterinarian about this option.
- Still have some questions? Contact us at firstname.lastname@example.org and we will do everything we can to assist.
- Calcium chloride presentation at Alliance for Contraception of Cats and Dogs 5th International Symposium, June 2013 from the Parsemus Foundation on Vimeo.
- Alliance for Contraception of Cats and Dogs 5th International Symposium: Getting Involved in Field Testing Session from PCMA on Vimeo. The “Could your organization use Calcium Chloride? Nuts and Bolts” talk begins at 37:54.
- Animal Grantmakers 2014 Conference – Ruth Steinberger Spay/Neuter Presentation from the Parsemus Foundation on Vimeo, for tips on nonsurgical neuter in context and best practice.
- Downloadable bibliography with information from 1977 to the present.
- Several key papers (Jana & Samanta, 2011 study in cats; Leoci et al., 2014 studies in dogs; and 2019 intraepididymal study in dogs) were supported by the Parsemus Foundation and are available open access. Several unpublished reports (goats, pet rat) are also available.
An independent review of the data
Veterinarians Offering Alternative Methods of Contraception
Looking for a veterinarian willing to perform procedures beyond surgical spay or neuter? Browse our directory of qualified veterinary professionals.
Do you offer alternative methods of contraception like ovary-sparing spay and vasectomy? Join our referral directory so new clients can find you.
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