Librela has become one of the most talked-about developments in veterinary medicine in recent years. For many dogs with arthritis, it has made a real and welcome difference. For others, and their owners, expectations may not have been borne out.
As a veterinary pain clinician, I think it is worth setting out what we currently know about this drug as clearly and honestly as possible, including the uncertainties. The picture is more nuanced than either the enthusiastic promotion or the alarmed commentary online might suggest.
What is Librela and how does it work?
Librela is the brand name for bedinvetmab, a monoclonal antibody developed by Zoetis. It was approved in Europe in 2020 and in the United States in 2023 for the management of osteoarthritis pain in dogs (Zoetis, 2024). It is given as a monthly injection under the skin.
It works by targeting a protein called Nerve Growth Factor (NGF). NGF plays an important role in how pain signals are generated and amplified in arthritic joints. By binding to NGF and blocking its activity, Librela reduces the pain signals reaching the brain, without the anti-inflammatory mechanism of NSAIDs (non-steroidal anti-inflammatory drugs such as meloxicam or carprofen) (Monteiro et al., 2025).
This is a genuinely novel approach. NSAIDs have been the mainstay of arthritis pain management in dogs for decades, and they work well for many patients. Gastrointestinal side effects can be common and may limit use of these treatments in some cases, Rare and very rare side effects which have been associated with NSAID use include liver and kidney issues. Librela offered a different mechanism of action, a different route of administration, and potentially a useful option where NSAIDs alone were not doing enough.
Does it work?
For most dogs, the evidence is encouraging. A prospective, randomised, placebo-controlled clinical trial demonstrated that bedinvetmab significantly reduced pain scores compared to placebo, with treatment success rates of 36% at day 14 rising to 50% by day 56, compared to 9% and 19% at these time points for placebo (Corral et al., 2021). A large multisite field study conducted across the USA confirmed these findings, showing statistically significant improvements in owner-assessed pain measures (Michels et al., 2023).
More recently, a randomised controlled trial found Librela to be non-inferior to meloxicam, a commonly prescribed NSAID, for managing canine osteoarthritis pain, with a lower risk of gastrointestinal side effects (Innes et al., 2025). This is a meaningful finding. A drug that achieves similar results to the established gold standard treatment, via a completely different mechanism, offers real clinical value.
The monthly injection format is also convenient, both for dogs who struggle with daily tablets and for owners who find daily medication management difficult.
What are the concerns?
Two distinct sets of concerns have emerged from post-marketing experience (that is, from real-world use after the drug was approved).
Neurological adverse events
In December 2024, the US Food and Drug Administration (FDA) issued a formal “Dear Veterinarian” letter, a significant regulatory step, following reports of neurological adverse events in dogs treated with Librela. These included ataxia (unsteadiness, particularly in the hind legs), seizures, partial paralysis, urinary incontinence, and excessive thirst and urination (U.S. Food and Drug Administration, 2024).
The FDA’s review included a case series of 363 dogs with more than one neurological sign. Notably, around 73% of these dogs were over 10 years old, an age group already at higher risk of underlying neurological conditions independent of any medication. This does not mean Librela caused these events, but it is an important consideration when assessing the drug in older patients.
Based on a global pharmacovigilance study covering over 18 million doses, these neurological events are classified as rare to very rare, occurring in approximately 1 to 10 dogs per 10,000 treated (Monteiro et al., 2025).
Musculoskeletal concerns and the Farrell et al. study
The second area of concern was raised in 2025, by Farrell and colleagues who published a paper examining musculoskeletal adverse events in dogs receiving bedinvetmab (Farrell et al., 2025).
The study had two components. The first was a disproportionality analysis comparing musculoskeletal adverse event reports for Librela against six other osteoarthritis medications using the European Medicines Agency’s pharmacovigilance database, finding that ligament and tendon injuries, fractures, and polyarthritis were reported approximately nine times more frequently in Librela-treated dogs than in dogs receiving comparator drugs. The second was a case series of 19 dogs whose adverse event data was reviewed by an 18-member expert panel.
The findings of the case series were striking. The expert panel unanimously concluded a strong suspicion of a causal association between bedinvetmab and accelerated joint destruction in the 19 reviewed cases. The changes observed included significant bony proliferation, soft tissue ossification, and in some cases joint dislocation. The authors argued that this pattern was biologically plausible, stating that “Given NGF’s diverse roles and prior evidence of RPOA, subchondral bone fractures, and atraumatic joint luxations in humans and animals, bedinvetmab-associated MSAEs are an expected consequence of NGF inhibition”. (Farrell et al., 2025). Similar concern arose with a human anti-NGF drug, tanezumab, which ultimately failed to gain approval in part because of this issue.
However, it is important to read this study in context.
The disproportionality analysis (the statistical comparison) has been criticised on methodological grounds, including in a commentary by a researcher at the University of Glasgow, (Lloyd, 2025) and in a separate commentary by authors employed by Zoetis. The critics argue that the datasets used were not directly comparable, which would undermine the statistical conclusions. These are legitimate methodological concerns.
The case series of 19 dogs is harder to dismiss, but case series have inherent limitations: they cannot establish causation, and most of the dogs were also receiving concurrent NSAIDs, which complicates the attribution of joint changes to bedinvetmab alone.
In short: there are plausible biological mechanisms by which Librela could contribute to accelerated joint changes in some dogs, a credible expert panel that reviewed 19 cases and found a strong suspicion of association, and significant scientific debate about whether the statistical evidence supports the same conclusion at a population level.
The UK regulatory position: a significant update
In February 2026, the UK Veterinary Medicines Directorate (VMD) completed an in-depth assessment of Librela as part of its ongoing surveillance activities. The assessment covered death, arthritis with faster-than-expected progression, and human exposure, alongside routine assessment of lack of efficacy, recumbency, muscle weakness, tremor, and lameness.
The VMD confirmed that the medicine’s benefits continue to outweigh its risks for most dogs treated. However, as part of that review, the Summary of Product Characteristics (SPC), the official product label, was updated such that immune‑mediated polyarthritis, paresis and paralysis were added to Librela’s product information in January 2026, with a 3 February notice also introducing a special‑precaution to use caution in patients with specified immune‑mediated conditions.
In May 2026, The following were added as very rare adverse events (defined as fewer than 1 animal in 10,000 treated, where one dose equals one treated animal): joint swelling, joint pain, bone and joint disorder, and soft tissue ossification (Veterinary Medicines Directorate, 2026).
The updated label describes new bone formation affecting the periosteum, joint capsule and adjacent soft tissues following repeated administration. Radiographically, this appears as extensive, irregular periosteal and ectopic mineralised tissue formation extending beyond normal chondro-osseous margins into the metaphyseal and in some cases diaphyseal regions of adjacent bones. Focal osteolysis or erosions may also be observed. These changes may present unilaterally or bilaterally, can affect multiple joints, may be progressive, and in very rare cases have been associated with fracture (Veterinary Medicines Directorate, 2026).
In plain language: in a very small number of dogs, Librela may have been associated with abnormal new bone growth and joint destruction that can affect one or several joints, may worsen over time, and has in rare cases led to fracture.
The SPC was also updated to add clinical guidance in the special precautions section: where a dog presents with new or increased joint swelling and/or joint pain following Librela treatment, consideration should be given to performing additional diagnostics and discontinuing treatment on a case-by-case basis (Veterinary Medicines Directorate, 2026).
This is now the official clinical guidance from the UK regulator: not a recommendation from a study or a specialist opinion, but a formal precaution embedded in the product label.
Immune reactions
Because bedinvetmab is a foreign protein, there is a small risk of an immune reaction. Hypersensitivity reactions are listed as very rare in the SPC (Veterinary Medicines Directorate, 2026).
Who should not receive Librela?
Librela is not recommended for breeding, pregnant, or lactating dogs, or for dogs with a known hypersensitivity to bedinvetmab (Veterinary Medicines Directorate, 2026). The FDA’s review noted that dogs with pre-existing neurological signs warrant careful consideration prior to treatment (U.S. Food and Drug Administration, 2024). Given the newly documented bone and joint changes, dogs with pre-existing joint instability, advanced structural joint disease, or a history of fracture should be discussed with your vet in detail before starting or continuing treatment (Veterinary Medicines Directorate, 2026; Farrell et al., 2025).
What does this mean in practice?
Librela remains a useful drug for the right patient, but one that should now be used with careful patient selection and monitoring.
Things worth discussing with your vet if your dog is on Librela or being considered for it:
Is Librela appropriate for this dog? Dogs with pre-existing neurological conditions, significant joint instability, or severe structural joint disease may warrant more caution.
Is the dog being monitored? Regular reassessment of gait, joint health, and any new neurological signs is sensible in any dog on long-term medication. Following the VMD’s 2026 SPC update, there is now a specific red flag to be aware of: if your dog develops new or increased joint swelling or joint pain while on Librela, this should prompt additional diagnostics and a conversation with your vet about whether to continue treatment. (Veterinary Medicines Directorate, 2026).
Is the benefit real and sustained? If Librela is working well and the dog is clearly more comfortable with no concerning signs, the benefit-risk balance is likely favourable. If the response has been limited, it is worth reviewing whether to continue or whether alternative treatments should be considered.
Is concurrent NSAID use necessary? Most of the dogs in the Farrell case series were receiving both Librela and NSAIDs. Whether concurrent use increases risk is not established, but it is worth discussing with your vet whether both are needed (Farrell et al., 2025).
What to watch for at home. Contact your vet promptly if you notice any of the following after a Librela injection:
- Sudden or progressive unsteadiness, wobbling, or loss of coordination
- Seizures or collapse
- New or worsening joint swelling or joint pain
- Lameness that develops or worsens after starting treatment
- Marked reduction in appetite or unusual lethargy
- Changes in urination habits, including incontinence
- Persistent vomiting or diarrhoea
Your vet can report any suspected adverse reactions to the VMD and to the manufacturer, which directly contributes to ongoing safety monitoring for all dogs receiving this treatment.
The broader picture
It is worth remembering that all effective medications and interventions, including acupuncture (Lai et al., 2025) and laser, carry some risk of adverse effects in some patients. NSAIDs, which have been used in dogs for decades and are generally well tolerated, can cause serious kidney, liver, and gastrointestinal problems in a minority of patients. The existence of adverse events does not make a drug unsuitable. Careful patient selection, monitoring, and informed consent are essential for any long-term medication.
What the Librela safety discussion does highlight is the value of robust post-marketing surveillance, of specialist-led pharmacovigilance, and of vets and owners reporting adverse events when they occur. The concerns that have emerged have done so because people paid attention and reported what they were seeing.
A note on the science
The debate around the Farrell et al. study, with commentaries from independent academics, from the manufacturer, and from supporting authors, is science working as it should. Peer-reviewed papers get challenged, methodology gets scrutinised, and the evidence base develops over time. Owners reading alarming social media posts about Librela should know that the scientific community is actively and rigorously examining these questions.
At the time of writing (May 2026), there is no regulatory withdrawal of Librela in any market. The VMD’s 2026 assessment confirmed the benefit-risk balance remains positive for most dogs. The FDA and EMA continue to monitor the situation. The UK SPC update represents an important step in the ongoing process of refining how this drug is used safely. Further large-scale studies are needed and are expected.
If your dog is on Librela
Do not stop any medication without speaking to your vet first. If you have concerns, discuss them at your next appointment.
If you are considering a pain review for your pet we are accepting cases with a wait time of around one week. You can either request a referral from your vet or, once you’ve booked, we will liaise with your vet to request permission to accept the referral and obtain your pet’s medical history, so there’s nothing extra for you to arrange. Your pet will remain registered with their own vet for all other care.
Book an initial appointment at the Dulverton clinic
Not local to Somerset or Devon? I offer online consultations for dogs and cats anywhere in the UK. You can either request a referral from your vet or, once you’ve booked, we will liaise with your vet to request permission to accept the referral and obtain your pet’s medical history, so there’s nothing extra for you to arrange. Your pet will remain registered with their own vet for all other care.
References
Corral, M. J. et al. A prospective, randomized, blinded, placebo-controlled multisite clinical study of bedinvetmab, a canine monoclonal antibody targeting nerve growth factor, in dogs with osteoarthritis. Vet Anaesth Analg 48, 943–955 (2021).
Farrell, M., Waibel, F.W.A., Carrera, I., Spattini, G., Clark, L., Adams, R.J. et al. (2025) ‘Musculoskeletal adverse events in dogs receiving bedinvetmab (Librela)’, Frontiers in Veterinary Science, 12, p. 1581490. doi: 10.3389/fvets.2025.1581490.
Innes, J. F. et al. A randomised, parallel-group clinical trial comparing bedinvetmab to meloxicam for the management of canine osteoarthritis. Front. Vet. Sci. 12, 1502218 (2025).
Lai, M. LE., Machin, H. & Adami, C. A survey study on the use of veterinary acupuncture in the UK and Europe. Vet. Anaesth. Analg. 52, 604–612 (2025).
Lloyd, A. Commentary: Musculoskeletal adverse events in dogs receiving bedinvetmab (Librela). Front. Vet. Sci. 12, 1649240 (2025).
Michels GM, Honsberger NA, Walters RR, Tena JKS, Cleaver DM, A prospective, randomized, double-blind, placebo-controlled multisite, parallel-group field study in dogs with osteoarthritis conducted in the United States of America evaluating bedinvetmab, a canine anti-nerve growth factor monoclonal antibody, Veterinary Anaesthesia and Analgesia, https://doi.org/10.1016/j.vaa.2023.06.003.
Monteiro, B. P. et al. Global pharmacovigilance reporting of the first monoclonal antibody for canine osteoarthritis: a case study with bedinvetmab (LibrelaTM). Front. Vet. Sci. 12, 1558222 (2025).
U.S. Food and Drug Administration (2024) Dear veterinarian letter notifying veterinarians about adverse events reported in dogs treated with Librela (bedinvetmab injection). FDA Center for Veterinary Medicine. Available at: https://www.fda.gov/animal-veterinary/product-safety-information/dear-veterinarian-letter-notifying-veterinarians-about-adverse-events-reported-dogs-treated-librela (Accessed: 20 May 2026).
Veterinary Medicines Directorate (2026) Summary of product characteristics: Librela 20 mg/mL solution for injection for dogs, https://www.vmd.defra.gov.uk/productinformationdatabase/files/SPC_Documents/SPC_2310388.PDF (accessed 24th May 2026).
