My recent articles have been about depressing topics. Sudden death. Home burials. Constipation. I promised my editor I would write something more cheerful soon. So here it is. There is a new medication now approved for use in dogs with osteoarthritis. It’s called Librela, and according to the manufacturer, it is the “first and only monthly infectable anti-NGF monoclonal antibody therapy for control of canine osteoarthritic (OS) pain.” Well, that’s a mouthful. What does that mean? How does it work? How much does it cost? Is it right for your old, gimpy golden retriever, Geezer?
Let’s start with the science and defining our terms. Osteoarthritis (OA), also known as degenerative joint disease (DJD), is an irreversible disease of the joints characterized by degeneration of the cartilage that protects the articulation of the bones. Other changes ensue, including inflammation, formation of little bony bits called osteophytes, and fibrosis around the joints. These changes cause pain, and often affect Geezer’s mobility. Which brings us to … anti-NGF monoclonal antibodies. NGF stands for nerve growth factor. Hang in there with me.
Say Geezer has arthritis in his knees. First of all, remember that “knees” (technically called the stifles) in dogs are in their hind legs. It can get pretty confusing, because in animals that “kneel down,” such as horses, camels, and elephants, people call that bendy joint in the front legs the “knees.” But Geezer’s knees are in his hind legs, and are prone to all kinds of issues in old dogs, ranging from instability and damage from injuries such as cruciate ligament tears to congenital conditions like luxating kneecaps. But we could actually talk about any arthritic joint — hips, shoulders, hocks, and so on. The mechanism is always the same. As the cartilage lining the joint breaks down, it releases chemicals called pro-inflammatory mediators. These go to the peripheral nerves and send signals that travel up to the spinal cord, and eventually to the brain, letting Geezer know that his knees (hips, shoulders, hocks) hurt.
If you’re still with me, you were probably a science nerd in high school. One more paragraph of sciencey stuff. Isn’t this fun? Nerve growth factor (NFG) is the “signaling” protein produced by the injured tissues that acts in several ways, leading to more inflammation and more pain. But here comes Librela to the rescue. The active ingredient is bedinvetmab, a type of protein that can recognize and bind to the NGF. This prevents the NGF from attaching to the receptors on the nerve cells, thus interrupting the transmission of the pain signals. One quick monthly injection of Librela given subcutaneously (under the skin) may thus reduce pain in whatever joints are affected, increasing mobility, and improving Geezer’s quality of life.
Sounds too good to be true, doesn’t it? Well, there are a few caveats. In the clinical field trials, although many dogs showed reduced pain within a week of the first injection, some needed a minimum of two injections a month apart before Librela reached maximum effect. And some dogs did not seem to benefit at all. It’s hard to assess for sure. We can’t ask Geezer, “How would you rate your pain today on a scale of one to 10?” Researchers had to rely on the human owners’ perceptions, using a standardized survey called the Canine Brief Pain Assessment. Yes, science nerds, there was a placebo control group as well. The Librela group had better outcomes than those in the placebo trial, in every case.
What about side effects? There were very few reported, and most were fairly similar in frequency to what was seen in the placebo group. Most were things that are common in geriatric dog populations, such as urinary tract infection or lethargy. One study done in Europe showed an increase in blood urea nitrogens, a renal function parameter, but in the vast majority of those cases, this was not associated with any clinical signs or other effects on the kidneys.
When any new product hits the market, I tend to be conservative, sitting back and waiting to see if more problems are reported with wider usage. There has been a lot of discussion on veterinary social media sites. I have read a few anecdotal cases of dogs who declined rapidly after Librela, but the reality is that there are millions of other reasons why elderly dogs might have a rapid decline. What I always remind the sometimes not-so-scientific nonmedical population is that correlation does not equal causation. In other words, these rare occurrences may have been coincidental, unrelated to Librela. Nonetheless, continued monitoring of such reports is warranted.
Other things Geezer’s owner should know? Librela is contraindicated in breeding, pregnant, and nursing dogs. Allergic reactions are possible, though rare. No studies have been done about concurrent use with other medications, or simultaneous vaccinations. In people, rapidly progressing osteoarthritis occurred in a very small number of patients receiving the human form of anti-NGF monoclonal antibody therapy, though this has not been reported in dogs. Finally, price: Librela is moderately expensive. Cost varies with the size of your dog, but you can expect to pay anywhere from $70 to over $100 per month. Compared with the cost of daily NSAIDS, that’s actually not bad.
Most of the discussions I am reading from fellow veterinarians worldwide report remarkable improvement in quality of life in many cases. It has been used in Europe for more than two years, with over 4 million doses given. It’s not a magic cure. In some reports, fewer than half of owners thought it helped, but in other studies, it was closer to 60 percent. Librela is certainly a good new option to try, especially for palliative care in geriatric patients so crippled by osteoarthritis that they are no longer enjoying life. I intend to use caution in considering this medication, but for many old Geezers, it appears that the potential benefits far outweigh the risks.