Two Guinea pigs on hands

Small Animal Nonsurgical Sterilization

Calcium chloride nonsurgical sterilant for “pocket pets”

Calcium chloride dihydrate (CaCl2) is a common chemical that has been used as a nonsurgical sterilant in male dogs, cats, rats and other species (see bibliography). The chemical injection results in sterility, and may be particularly suited to use in small animals, such as rats, guinea pigs, hamsters and rabbits.

This page provides more information on the use of CaCl2 in pocket pets, but should be considered in conjunction with more complete information and cautions on the use of calcium chloride as a chemosterilant in dogs.

Calcium chloride as a chemosterilant

The use of CaCl2 for male sterilization has several important benefits: it is nonsurgical, inexpensive and requires few physical resources. This makes calcium chloride a method to consider in low-resource environments.

The technique involves injection of the calcium chloride solution into each testicle while the animal is lightly sedated (to reduce movement). The chemical kills the tissue of the testicle resulting in sterility. Given this necrotizing effect, it is important that none of the solution escapes the testicular capsule onto healthy tissue. The testicles often swell initially, followed by significant shrinkage in size and reduction in testosterone levels.

Large-scale, controlled studies of CaCl2 directed by Drs. Jana (India) and Leoci (Italy) were very successful in producing azoospermia (no sperm in semen) and significant reductions in testosterone, with few complications, in dogs. A solution of 20% CaCl2 in ethyl alcohol was found to be an optimal solution for dog chemosterilization (Leoci et al., 2014).

Use in field settings resulted in some complications, possibly as a result of variations in injection technique, characteristics of the animal being treated, follow-up care, or other unknown variables. Less success has been experienced in animals with large testicles, as it is challenging to obtain adequate coverage of the CaCl2 solution throughout a large testicular volume without leaking.
Pet rabbit

Studies evaluating calcium chloride in small animals

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.

CaCl2 has been used experimentally in rats with good success. 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. Here are the details:

  • Two dose-finding studies on 60 male albino rats concluded that 10-20 mg  of CaCl2 in saline produced infertility, measured by epididymal sperm count and mating studies (Jana et al., 2002; Jana & Samanta, 2006).
  • A study of intratesticular injection of guinea pigs with 15 mg/100g weight of CaCl2 in lidocaine, provided as one injection or three daily doses, resulted in significantly decreased testosterone and sperm count, but not azoospermia (Sen et al., 2017). No fertility assessment was completed.
  • A recent large-scale study of intratesticular injection of 20% CaCl2 in 0.5% dimethyl sulfoxide (DMSO) in 96 rats was completed by researchers in Brazil. One hundred days after the injection, rats were azoospermic, infertile, and evidenced testicular atrophy (Paranzini, 2019). Only one rat had complications.
  • A pet rat was injected with 20% CaCl2 in 95% ethyl alcohol without complications. Significant reduction in testicular volume resulted although fertility was not assessed. See description of this project.

Details of using calcium chloride in rats

Woman with rat on her shoulder
Most of the information using calcium chloride solutions for nonsurgical sterilization of small animals was conducted in rats. We have very little information in other small animals.

Procedures for sterilizing rats using calcium chloride:

Preparation – Calcium chloride sterilant has been used in a number of solutions, including saline, lidocaine, DMSO and alcohol. Work in dogs found that alcohol served as the a better diluent than lidocaine (see Leoci et al., 2014). In rats, a 20% CaCl solution (or  10-20 mg CaCl2 per 100 g body weight) was found to be effective.

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 withdrawing the needle, taking 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 (see images below). 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.

Images illustrating the shrinking of the testicular tissues following injection of CaCl2 in saline in a study on rats (credit to Dr. Kuladip Jana).

Next steps?

Parsemus Foundation is looking for individuals interested in collaborating on a small proof-of-concept study using CaCl2 in alcohol in guinea pigs. Please send a message to info@parsemusfoundation.org for more information.

Bibliography

Jana K, Samanta PK, Ghosh D. (2002) Dose-dependent response to an intratesticular injection of
calcium chloride for induction of chemosterilization in adult albino rats. Vet Res Comm.
26(8):651-673. (abstract)

Jana K, Samanta PK. (2006) Evaluation of single intratesticular injection of calcium chloride for
nonsurgical sterilization in adult albino rats. Contraception 73:289– 300. (full text download)

Leoci R, Aiudi G, Silvestre F, Lissner E, Lacalandra G. (2014) Alcohol diluent provides the optimal formulation for calcium chloride non-surgical sterilization in dogs. Acta Veterinaria Scandinavica, 56:62. (full text download)

Paranzini CS. (2019) Effects of calcium chloride with DMSO injection on testicular function and fertility in rats. 120 p. Thesis (PhD Degree in Animal Biotechnology) – Faculdade de Medicina Veterinária e Zootecnia, Campus Botucatu, Universidade Estadual Paulista.

Sen CC, Yumusak N, Faundez R, Temamogullari F, Taskin A. (2017) Evaluation of intra-testicular injections of calcium chloride and 4-vinylcyclohexene 1, 2 monoepoxide for chemical sterilization in guinea pigs. Polish J Vet Sci, 20(2):251-260. (full text download)

Calcium chloride chemical castration in the rat: A possible solution for pocket pets? (2019) Parsemus Foundation. (full text download)