I have written before about Librela for dogs and Solensia for cats. These drugs block nerve growth factor, or NGF, which helps the body sense pain. A new study looked at what happened when researchers gave Librela to horses.
The finding is simple: Librela was still in the blood of two horses 34 days after one injection. That was the last day researchers tested them, so we do not know how much longer it remained.
This is a long time, because the half-life of the drug (in dogs and cats) is around 19 days.
Why give Librela to horses in a study?
Librela, also called bedinvetmab, is made for dogs with arthritis pain. Researchers wanted to learn how long a lab could find it in a horse’s blood. This matters for horse sports, where a drug that hides pain could allow an injured horse to keep training or competing.
They gave one injection to three healthy, retired Thoroughbred geldings and took blood samples over 34 days. In two horses, Librela was still detectable on day 34. In the third, it was last detected on day 5.
This was a drug testing study. It did not measure pain relief, joint damage, or long-term safety in horses.
Why am I concerned about joint health?
Pain is unpleasant, but it can also warn an animal that a joint needs care. A horse that feels less pain may put more weight on a damaged joint. Less pain does not mean that joint has healed.
Studies in dogs give us more reason to ask questions. In 2025, Farrell and colleagues described serious joint and bone changes in dogs that had received Librela. Some raised concern for rapidly progressive osteoarthritis (RPOA), which means a joint breaks down much faster than expected.
A 2026 study by Budsberg and colleagues described an unusual pattern of bone change around joints in dogs treated with Librela. The authors called it abnormal periarticular bone remodeling (APBR). These dog reports raise a safety question. They do not prove that Librela caused every change, and they do not show that the same changes occur in horses.
I also recently discussed a paper that asks whether blocking NGF might do more than reduce pain. The authors suggest it could also affect the signals that help bone respond to stress. A joint might then face more use while having less support for adapting to that use. This is a hypothesis that still needs testing, including in horses.
What should we take from the horse study?
It shows that Librela can remain detectable in a horse’s blood for at least 34 days after one injection. It helps laboratories plan tests for horse sports.
It does not tell us whether Librela helps horses with pain or whether it can cause RPOA, APBR, or other joint changes in them. Three healthy horses followed for blood levels cannot answer those questions.
For me, the concern is especially clear in a working or sport horse: if a drug reduces pain, we must also know what happens to the joints under continued work. We need studies that follow both comfort and joint health before considering an anti-NGF drug a safe treatment for horses.
Source: Cheung HW and colleagues. “Administration Study of Bedinvetmab, an Antinerve Growth Factor Monoclonal Antibody, in Horses for Doping Control Purposes.” Drug Testing and Analysis, 2026. Read the study.
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