Finally: A Nonsurgical Method to Neuter Dogs

A drug called Zeuterin sterilizes male dogs with a simple injection into the testicles.


For years, one of veterinary medicine’s Holy Grails has been the search for an injectable substance that will permanently sterilize animals without surgery. With more animal rescue groups doing dog’s work around the globe, including rescuing dogs in Thailand bound for dinner tables, the need to desex large numbers of animals for population control has never been more critical.

A company now offers an injectable sterilant that will neuter a male dog (or cat) without surgery. It’s called Zeuterin, made by Ark Sciences, and after more than 20 years of testing, it’s scheduled to be available by the end of this year — pending FDA approval, which expected in the coming months.

Here’s how it works: The formula, a spermicidal combination of zinc gluconate and arginine (an amino acid), is injected directly into the animal’s testicles. (Hence the name Zeuterin, derived from “zinc neutering.”) Zeuterin causes irreversible fibrosis (scar tissue) over the testes, which atrophy and shrink, yet remain visible.

Only those veterinarians who’ve received training from Ark Sciences can get Zueterin. It’s effective for permanent sterilization of male dogs at least 3 months old. It has been approved for animals 3 to 10 months old, but Ark Sciences believes Zeuterin will also be approved for use in dogs of any age.

Here’s a video of a dog named Max getting Zeutered in San Francisco last year. (Caution: Video might not be appropriate for those squeamish about needles.)

Another dog named Max, a Welsh terrier owned by April Patrick of New York, was Zeutered two weeks ago. In May, Patrick read about Zeuterin online; after a lifetime of caring for companion animals, she liked nonsurgical option because it’s less invasive than surgical castration. When she contacted Ark Sciences to add Max’s name to the waiting list, Patrick was “surprised they got back to me so quickly.” The company reached out to her vet to offer certification in administering the injections, and after the vet was trained, Max’s appointment was scheduled.

“I was right there with Max, they explained everything to me and discussed the after-care,” Patrick says. “The procedure was surprisingly quick, just like getting a shot. They gave him a sedative, he went under for the injections, and that was it. I picked him up and took him outside; he started to come to, and in about 10 minutes he was awake but a little groggy. He got his appetite back in 12 hours, and after 24 hours he was up and trying to run! It was so by-the-book, I couldn’t believe it.”

Patrick’s dad had reservations about having Max neutered, fearing it would alter his personality. Now, Patrick reports, after observing Max since the procedure, even her Dad is starting to come around. “You can already see the effect of the testosterone decreasing, but Max has kept his personality,” she says. “Honestly, I believe this will be the future of neutering. It’s faster and easier on the dog.”

Plus, for male dog owners who wince at the very idea of castration — and, let’s face it, that’s a lot of male dog owners — Zeuterin is a much more appealing option, as it leaves the testicles in place, so the dog maintains a virile appearance. In fact, because Zeutered dogs look no different than intact males, they receive a small tattoo on the inner groin to prove that they’re incapable of reproducing.

Most animal shelters and low-cost spay-neuter facilities don’t have post-surgical recovery space for animal patients, so Zeuterin is a dogsend, which will save time and money for rescuers — and the resources saved can be put toward other projects, such as spaying female dogs. The injections are administered on an outpatient basis, there’s no anesthesia involved (just a sedative), and dogs are released quickly after the procedure. Ark Sciences has generously donated the procedure to numerous animal shelters across the country and around the world, from Mexico City animal shelters to New Jersey’s Liberty Humane Society, where the vets are trained to administer the injections.

Tod Emko, founder of the nonprofit Darwin Animal Doctors, which brings veterinary care to the animals of the Galapagos, is in talks with Ark Sciences about training the Darwin Animal Doctors volunteer vets. He’s excited by Zeuterin’s potential: “The ideal surgical equipment for spay/neuter is extremely hard to bring to Galapagos,” he explains, “and the population of dogs and cats is exploding at a staggering rate. A non-surgical method to sterilize the overpopulating pet problem would be a dream solution.”

“Most people have no idea there are even dogs and cats on the Galapagos to begin with,” Emko adds. “The truth is, there are thousands of them on the islands. If we want to protect this precious UN World Heritage Site, we need a way to sterilize a large numbers of these animals, and fast.”

Would you opt for Zeuterin or do you prefer old-school surgical neutering? Let us know in the comments.

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