Zeuterin or Neutersol to
chemically sterilize male dogs

Zeuterin injectable is a non-surgical technique used to render male dogs 3 to 10 months old unable to reproduce. This is not a new procedure or product– it was introduced under the label Neutersol in 2003 and is also marketed in other countries as Esterilsol.

At Veterinary Village, our doctors have elected to only use traditional neutering or vasectomy techniques to keep dogs from reproducing. Both are surgical procedures known to be safe and effective.

When a dog is surgically neutered, both testicles are removed through a single incision while the dog is under general anesthesia. This is a short procedure taking approximately 10 minutes. Dogs who are neutered no longer produce testosterone, are protected against developing testicular tumors, perianal tumors, perineal hernias, and benign prostatic hypertrophy, a common syndrome in males over age 5. They also have minimal sex drive and associated behaviors such as roaming after females in heat and territorial leg lifting. Other behaviors such as aggression and fearfulness are variable and are still under discussion as to whether neutering has a positive or negative effect on the neutered dog. Neutering does not protect against prostate cancer, which is more rare in the dog than in humans.

When a dog is vasectomized, the testicles are preserved in the scrotum but the vas deferns is transected so sperm cannot transfer to a female dog. The vasectomized dog will retain his testosterone levels, still has a drive to mate and may exhibit other male behaviors such as leg lifting and roaming. He may also be at risk of testicular tumors, benign prostatic hypertrophy, perianal tumors, and perineal hernias.

Recent studies suggest that dogs who retain testosterone levels have lower risk of obesity, joint disease, thyroid disease and cancer (except testicular cancer, usually benign in the dog). For these reasons, many clients have decided to wait to neuter their dogs until they are older or have a vasectomy instead of traditional neutering. Golden Retrievers seem to be particularly sensitive to the negative effects of neutering.

Zeuterin is a zinc gluconate solution, injected directly into each testicle. It is being promoted as painless and not requiring anesthesia, sedation or post injection pain medications. The doctors at Veterinary Village are not convinced that this is the case, as the tunic around the testicle is not made to stretch with the increased volume after the injection. We are concerned that dogs receiving Zeuterin are not receiving adequate anesthesia and pain management at the time of or following the injection. Known complications include pain, allergic reactions, inflammation of the surrounding skin, and self-mutilation. This procedure cannot be used on dogs with testes that did not descend normally into the scrotum.

Although sperm are not produced after the dog has developed scar tissue from the zinc injection, the dog still produces approximately 50% of the testosterone they would without the injection. This means they may still develop sexual behaviors, testicular tumors, benign prostatic hypertrophy, perianal tumors and perineal hernias. It may be difficult to assess if the dog is incapable of reproduction or has abnormal feeling testes because of this injection or if the changes in the testicle are due to other causes of disease. The long-term effects of this injection are not yet known - a study monitoring the lifetime effects will take up to 16 years for full assessment. Despite this, the drug has been approved by the FDA. In canine social settings such as dog parks, pet stores, and doggie day care, the dogs will still pursue sexual behaviors and appear to be sexually intact, setting humans and other dogs up to be stressed.

For these reasons, the doctors at Veterinary Village have decided to be cautious with your pet’s care and continue to employ the known outcomes created by either neutering surgically or vasectomizing your male dogs.

Please contact us at 920-269-4000 or vv@k9stork.com if you have questions about neutering or any other veterinary care.