Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Chemical Sterilization a New Option for Male Puppies


Pet Column for the week of February 16, 2004


Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ann Marie Falk
Information Specialist

Sterilization helps combat the pet overpopulation problem and also curbs unwanted behaviors in dogs not selected for breeding. In the past the only way to stop a dog from fathering litter after litter of unwanted puppies was surgical castration. Now a new option exists: Neutersol, an injected chemical sterilization product.

Neutersol is currently labeled for use only in male dogs between the ages of 3 and 10 months with an appropriate testicle size. It is available by prescription from a veterinarian and should be given only by a veterinarian or other person trained in giving these injections.

"One advantage of using Neutersol is avoiding the hassle of surgery," says Dr. Cliff Shipley, a veterinary theriogenologist (reproduction specialist) at the University of Illinois Veterinary Teaching Hospital in Urbana. "Dogs do not need to be anesthetized or to stay at the clinic afterward for observation. They do not face the risks, such as bleeding, that accompany anesthesia and surgery. Giving an injection is easier than surgery any day!"

As with any medication there are possible side effects, however. Testicular swelling is a common reaction to the injection. Some dogs will experience a short painful period and may vomit. Other possible reactions include biting or licking the scrotum, swelling of surrounding tissue, skin irritation, and rarely infection.

"The complication rate is very, very low, and most problems are due to inappropriate injection," says Dr. Shipley. It is important that the person administering the injection be trained.

Studies show that Neutersol gets an "A+" in effectiveness for birth control: in a study 99.6 percent of dogs became sterile after an injection. It takes at least 60 days for the product to work, however. Neutersol does not kill sperm already in the body at the time of injection.

"Owners' No. 1 reason for neutering their male dogs is behavior, and the close second is unwanted puppies," says Dr. Shipley. "Testosterone, which may trigger these negative behaviors, is not completely eliminated by Neutersol in all dogs. Testosterone levels were decreased an average of 41 to 52% in the treated versus control subjects in the company's clinical trials."

"If Neutersol does not bring about the desired behavioral changes, owners can decide to have the testicles taken out," he says. "But even with surgical castration, when the source of testosterone is removed, behavior is not always altered. There is no guarantee that any form of castration will always change behavior."

Neutersol may be a good choice for dog owners who do not want the testicles removed. Some owners view castration as taking their dog's "manhood," while others like male dogs to look like male dogs. Dogs sterilized with Neutersol are no longer able to have puppies yet still have testicles and look like intact dogs.

"Neutersol is still a very new product and may not be the best choice in every situation," says Dr. Shipley. "It may have a more prominent role in animal shelters than in private practice. It will allow shelter veterinarians to sterilize more dogs is a much shorter period."

At this time Neutersol is still expensive, costing about the same as a surgical neuter. Your veterinarian can help you decide whether this product is best for you and your dog.

For now there is no product comparable to Neutersol for female dogs; the surgical spay procedure is the best option for female pets not being bred. Nor has Neutersol been approved in cats; similar doses to those given in dogs do not cause sterilization in cats. Studies are looking at the use of this product in large animals.

For more information on Neutersol or castration, contact your local veterinarian.