An arthritis drug helps old dogs, but some owners worry about side effects

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Around the country, veterinarians are prescribing a breakthrough new arthritis drug for dogs - Librela - which is helping aging pets get moving again by easing the aches and pains of osteoarthritis.

Ana Maria Cepeda, a veterinarian at North River Animal Hospital in Parrish, Fla., said her first patient was her 14-year-old pit bull mix who in the past has relied on a concoction of pain medication and supplements to cope with severe arthritis and joint issues. “It showed excellent promise on my own dog,” she said. “That gave me more confidence to start trying it in other dogs.”

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But not everyone is convinced. Fears about a range of side effects have spread rapidly on social media. A Facebook group shares stories from pet owners alleging that after being given the drug, their dogs had trouble walking or suffered kidney failure. An online petition has been circulating pushing to recall the drug until more study is done. The Food and Drug Administration says its reviewing reports of adverse events.

Veterinarians and the drugmaker say Librela has been shown to be safe and effective. A variety of factors may explain concerns about side effects, including the fact that the drugs are often used in older dogs, who may have a range of health issues.

We spoke to experts about Librela. Here’s what to know.

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What is Librela and how does it work?

Librela, made by Zoetis, is the brand name for a monthly injectable drug to treat canine osteoarthritis, a condition that affects an estimated 80 percent of all dogs 8 years or older and as many as 35 percent of dogs of all ages. The drug is an anti-nerve growth factor monoclonal antibody.

The drug’s active ingredient is called bedinvetmab, a monoclonal antibody designed to target nerve growth factor, or NGF, a naturally produced protein that’s important for fetal and early development of the nervous system. In adulthood, NGF plays a role in pain transmission and the release of pro-inflammatory molecules. It’s found in high levels in dogs with osteoarthritis.

Librela works by neutralizing NGF in the joint, essentially shutting down the pain pathway and lowering the overall amount of NGF produced. “It reduces how many signals are going to the brain saying, ‘Hey, this hurts,’” said Katie Bennett, an anesthesia and pain management specialist at the Veterinary Specialty Center in Bannockburn, Ill. It also helps alleviate swelling, which causes discomfort.

It’s recommended that dogs receive a minimum of two doses 28 days apart to determine if it can help reduce their pain.

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How long has Librela been available?

Librela launched in the United States in October, but it has been used in Europe for the last three years. A sister drug, Solensia, also by Zoetis, has been used to treat osteoarthritis in cats since 2022.

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What are the known side effects?

According to Zoetis, side effects can include bacterial skin infections, dermatitis and renal and urinary disorders, including urinary tract infections. In Europe, elevated blood urea nitrogen, which may indicate a kidney issue, was a side effect.

More than 12 million doses of Librela have been sold globally over the last three years, and a fraction of the dogs using Librela (less than 0.20 percent) have experienced “an adverse event,” said Robert Polzer, president of research and development at Zoetis.

Polzer described Librela as “a very safe product.” The company takes adverse events “very seriously,” Polzer said, and continues to collect and analyze data. “To date, we haven’t seen any signals emerge as far as causation between Librela” and the negative outcomes being reported, he said.

“Every medication, whether a human or companion animal medication, has the potential for risk and adverse events,” Polzer said. “Certainly for any pet owner who’s had that experience with their pets, we are quite empathetic.”

On social media, dog owners say their pups’ mobility appeared to decline after using the drug, citing hind leg paralysis in some cases and an inability to walk. Others say their dogs experienced anorexia, lost control of their bowels or experienced kidney issues after using the drug.

Veterinarians said any adverse events should be reported. But they emphasize the drug’s largely positive results.

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How much research has been conducted on Librela?

Two clinical trials in the United States and Europe recruited a total of 559 dogs and compared Librela with a placebo for three months each. Neither the dog owners nor the veterinary clinic personnel administering the doses knew if a pet was receiving the real treatment or a placebo.

In the U.S. study, 47.4 percent of dogs receiving Librela showed improvement after the first shot based on owner assessments, compared with 36.6 percent in the placebo group. In the European study, 43.5 percent improved after the first shot, compared with 16.9 percent on placebo. In both studies, the improvements were statistically meaningful. Adverse events were similar in the treatment and placebo groups. After three months of treatment in the European study, 89 dogs in the Librela group (63 percent) had responded positively based on owner and veterinarian assessments, and continued the treatment in a six-month open label phase of the study.

Anecdotally, veterinarians report success with the drug. Union Veterinary Clinic in Washington, D.C., has administered Librela to 49 dogs since October, and the majority are routinely receiving shots, according to Allison Gross, veterinarian and co-owner of the practice. Angell Animal Medical Center in Boston has administered approximately 350 shots, with largely positive results, said Susan O’Bell, veterinarian and internal medicine service director at Angell.

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What animals should be given the drug?

Patient selection is important, vets say. The drug should only be prescribed to healthy dogs diagnosed with osteoarthritis and is not recommended for dogs with kidney or neurological issues. The drug is not recommended for dogs who have limping or lameness from another cause, such as a cruciate tear, bone tumors or back or disc injuries. Librela is not recommended for dogs under 12 months, who are pregnant or lactating.

Most veterinarians recommend bloodwork, a urinalysis and possibly other diagnostic tests before prescribing. “A lot is dependent too on the conversations with the client and what their ultimate goal is,” Cepeda said. “Some people, it’s a quality-of-life issue, some people have difficulty medicating, and some people have tried everything under the sun and are desperate for something else.”

Osteoarthritis is a progressive disease, and vets say controlling chronic pain requires time and patience. See how your dog responds to Librela, and discuss with your vet lowering the dosage of other medications.

“It is not a quick fix, not a magic bullet,” Bennett said. “Clients will have to work at it for a couple of months to learn a sweet spot.”

Weight management, water therapy, physiotherapy, laser treatments, acupuncture and a number of other therapeutics can collectively help manage not just joint pain but the disease’s overall effect on the body. “This is the long haul,” O’Bell said. Librela is “one more thing we have in our arsenal.”

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How do you know if the drug is working?

Bennett asks owners to keep a daily journal of their dog’s progress and provides owners with a worksheet to measure improvement. Veterinarians suggest taking pictures and videos documenting changes in your dog’s body language, gait and demeanor.

Vets recommend trying two injections over two months before discontinuing Librela, which may not work for every patient. Some patients at Angell in Boston stopped Librela because owners did not see any big improvements, O’Bell said.

Bennett took her own senior dog off Librela after she developed a urinary tract infection. Not every dog will have a miraculous turn around, veterinarians caution. For some, the drug’s efficacy eventually wears off.

For dogs who regain their spark and spunk, experts advise easing them back into play. “Some dogs have become so active they injure themselves, because they go from not moving much at all to running around,” Gross said.

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Alexandra E. Petri is a freelance writer based in New York who has worked for the Los Angeles Times and the New York Times. Petri is a two-time reporting fellow with the International Women’s Media Foundation.

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