First U.S. use of calcium chloride provides dose for larger dogs

Calcium chloride is being used to non-surgically sterilize dogs and cats in a number of countries. Recently, veterinarians using CaCl2 in the US have confirmed that the decrease in testosterone level is equal to castration when using the proper dose and formulation. Testosterone levels below 0.5 ng/ml were confirmed at an accredited veterinary college following hCG challenge (a sensitive measure of the production of testosterone from testicular tissue which indicates if the Leydig cells are functional). A dosing chart for all sizes of dogs as well as mature cats has been created from this work. Further tests will be performed over the coming months and the results will be shared here. For more background and information on CaCl2 see the Calcium Chloride Male Sterilization page.

CaCl formulation:
The alcohol solution of 20% calcium chloride dihydrate was prepared by an accredited compounder as follows:
20 g of pharmaceutical grade CaCl2 [2H2O powder] was brought to a final volume of 100 ml of 95% pharmaceutical grade ethanol, mixed and delivered in a stopper- top sterile container.

Dosing chart:


Testicular widthDose per testicle
10-14 mm (and sexually mature adult cats)0.25ml (if testis feels overly full, STOP before full dose)
15-18 mm0.5ml
19-22 mm0.8ml to 1ml (continue to fullness)
23-24 mm1 ml to 1.5 ml (continue to fullness)
25-26 mm1.5 ml to 2 ml (continue to fullness)
27 mm and above1.5 ml to 2.5 ml (continue to fullness)


Recommendations include:

  1. Measure each testicle separately and accurately using a caliper.
  2. Wipe scrotum once with chlorhexidine solution mixed according to manufacturer’s instructions. If there is excessive dirt on the skin, clean only with mild soap and water.
  3. Pull maximum correct dose out of bottle (allowing for waste). Inject into testicle using a fresh 27 gauge needle for each testicle.
  4. Hold testicle, squeezing lightly for a few moments near the area of injection in order to ensure safe removal of the needle with no movement of CaCl.
  5. Mark dog with permanent marking near scrotum on lower abdomen (and/or for street dogs, with ear tag or ear whiting) in order to ensure the dog is identified as sterilized. For details on anesthesia-free options see the Marking Street Dogs page.
  6. The veterinarian should tell the pet owner, care giver or shelter manager to expect enlargement of the testicles for up to 10 days. Enlargement is not associated with pain, discomfort or lethargy.

The cost is under $1 per dog and includes CaCl, mild sedation, needles and syringes, tattoo paste

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