If you are reading this, your dog is probably on Librela (bedinvetmab) for osteoarthritis pain — or your veterinarian just suggested it — and you have seen something online that scared you. Owners search this drug alongside words like panting, increased drinking and urinating, ataxia, seizures, and death. Those searches land on a real regulatory story: in December 2024 the FDA issued a Dear Veterinarian letter about Librela, and in February 2025 the label was updated to add a post-approval adverse-event section and a client information sheet.

This article is specifically about side effects, adverse-event reporting, and the conversation to have with your veterinarian. For how Librela works, dosing, contraindications, and how it compares to NSAIDs, see our Librela for dogs guide; for how it stacks up against Adequan, see Adequan vs Librela.

Quick answer

Librela is a once-monthly injectable monoclonal antibody that targets nerve growth factor (NGF) to control osteoarthritis pain. It is not an NSAID, and because it is a protein it is broken down like a naturally occurring antibody rather than being processed by the liver or kidneys. For many dogs with OA it is an important option — particularly dogs who cannot tolerate NSAIDs.

It is not risk-free. In its December 16, 2024 letter, the FDA Center for Veterinary Medicine said its review of post-marketing reports identified neurologic signs (ataxia, seizures, paresis, recumbency, urinary incontinence), polyuria and polydipsia, and — in some cases — death, including euthanasia. Zoetis subsequently added a Post-Approval Experience section and a Client Information Sheet to the U.S. label. Those are the facts owners should start from. The harder question is what the reports prove, and that is where most online summaries stop being useful.

What the updated label tells owners

The Client Information Sheet added to the label in 2025 lists the side effects to watch for after an injection:

• Balance problems or trouble walking
• Weakness or trouble standing, or paralysis
• Seizures
• Drinking more (polydipsia)
• Urinating more (polyuria), or loss of bladder control
• Vomiting or diarrhea

The sheet states plainly that serious side effects can occur, with or without warning, and in some situations may result in death. The label also reinforces that Librela should not be used in dogs with known hypersensitivity to bedinvetmab, and should not be used in breeding, pregnant, or lactating dogs or in dogs under 12 months old.

What the FDA actually found

The FDA's December 2024 communication was based on a disproportionality analysis — a standard pharmacovigilance method that asks whether a given reaction shows up more often with one drug than with comparator drugs, beyond what reporting volume alone would predict. The agency identified roughly 18 safety signals, with neurologic signs (notably ataxia) and the urinary cluster (polydipsia, polyuria, urinary incontinence) standing out. Its Standard Adverse Event Review noted that the most frequently reported clinical signs in the case series were ataxia, anorexia, and lethargy.

It is important to understand what this kind of analysis can and cannot do. A disproportionality signal means "this combination shows up more than expected." It does not establish that the drug caused the sign, and the FDA said so explicitly. This is the same evidence framework regulators use for human drug safety, and it is a prompt for monitoring — not a verdict.

What the adverse-event reports show

VetMedGuide analyzed the public FDA CVM animal adverse-event database (extract dated June 8, 2026) for reports listing bedinvetmab. Because the agency masks brand names in this dataset, bedinvetmab — the active ingredient unique to Librela — is the reliable way to find these reports.

• About 17,900 reports listed bedinvetmab, essentially all in dogs (the product is approved for dogs; frunevetmab, sold as Solensia, is the feline anti-NGF equivalent).
• Roughly 62% were flagged as serious by the reporter.
• A urinary cluster — polydipsia, polyuria, urinary incontinence, or inappropriate urination — appeared in about 17% of reports. A neurologic cluster (ataxia, seizures, paresis, muscle weakness, recumbency, proprioception deficits) appeared in about 20%.
• The most common individual terms, in order, were death by euthanasia, lethargy, polydipsia, ataxia, vomiting, polyuria, seizures, diarrhea, and urinary incontinence.

These numbers are consistent with what the FDA flagged. They are also where the interpretation gets hard.

Why the death reports do not prove what they seem to

The single most alarming thing an owner reads is that death and euthanasia appear near the top of the list. Here is the context that matters.

First, most bedinvetmab reports involve more than one drug — in our analysis, about 58% of reports listed a concurrent medication. These are typically elderly dogs with advanced osteoarthritis who are also on NSAIDs, gabapentin, carprofen, grapiprant, or other chronic medications. When a 13-year-old arthritic dog on four drugs dies or is euthanized, attributing that outcome to one monthly injection is not scientifically possible from a report alone.

Second, the population itself carries baseline risk. The UK Veterinary Medicines Directorate (VMD), which conducted its own in-depth assessment of Librela, made exactly this point: the drug is used primarily in older dogs who often have diagnosed or undiagnosed concurrent disease and are receiving multiple medications. The VMD found that death following Librela administration is rare on the order of 1–10 per 10,000 treated animals. Zoetis reports that more than 25 million doses have been distributed globally and that no individual adverse event has been reported at a rate higher than "rare" as defined by the European Medicines Agency (fewer than 10 per 10,000 treated animals).

Third, regulators have not identified a proven biological mechanism by which bedinvetmab directly causes these outcomes. The VMD noted a small subset of older dogs that appeared to deteriorate within about 14 days of an injection, but found no consistent pattern in signs, dose number, or prior duration of treatment — some affected dogs had received Librela for years. Their conclusion: it is unclear whether the deterioration is product-related. That uncertainty is real and is worth knowing about; it is not the same as proven harm.

The honest summary: the reports justify heightened monitoring and the label change. They do not let anyone — defender or critic — claim certainty.

The pattern owners actually notice: panting, drinking, urinating

Two clusters show up both in the data and in what owners report anecdotally. The first is increased drinking and urination (polydipsia and polyuria), sometimes with urinary incontinence. This is widely recognized as the most characteristic real-world effect of Librela; the manufacturer does not attribute it to organ dysfunction but acknowledges the association, and the mechanism is not fully understood.

The second is panting. Panting is not prominent in the formal label lists, but it appears in roughly 5% of bedinvetmab reports in the dataset and is one of the most common things owners describe after an injection. It can reflect pain modulation, anxiety, or an effect we do not yet have a clean explanation for. If your dog begins panting persistently after starting Librela, that is worth a call — not because it is necessarily dangerous, but because your veterinarian can help judge whether it fits a benign expected pattern or warrants checking for something else.

How long Librela stays in the body

This matters for the side-effect conversation because, unlike a daily pill you can simply stop, a Librela injection is in the dog for weeks. The label half-life is on the order of 12–16 days, with steady-state reached after roughly two monthly doses. That long duration is part of why a single monthly shot controls chronic OA pain so well — and part of why an unwanted effect, if one occurs, can take days to several weeks to resolve as the body clears the antibody. There is no reversal agent. This is the reason the timing of monitoring (the first days to about two weeks after each injection) and prompt communication with your veterinarian matter more than for a short-acting oral drug. Reported effects do not appear to be cumulative in a simple dose-stacking way; the cases regulators have examined cluster shortly after an injection rather than building gradually across many doses.

Who is at higher risk

The label and the regulatory reviews point to dogs who deserve extra caution:

• Dogs with pre-existing neurologic disease — intervertebral disc disease, degenerative myelopathy, prior seizures, or unexplained hind-end weakness or ataxia. A new neurologic sign is much harder to interpret in these dogs, and several signals are neurologic.
• Older dogs on multiple medications, where disentangling cause is inherently difficult.
• Dogs who have reacted to a prior dose. The standard guidance is straightforward: if a dog has a reaction consistent with Librela, do not give it again.

What to ask your veterinarian

A good Librela conversation happens before the first injection and before each one after. Useful questions:

• Given my dog's age, blood work, and other medications, is Librela a reasonable choice, and what would make it not the right fit?
• What signs should I watch for in the first two weeks after the injection, and which ones mean I should call you the same day?
• If my dog already has neurologic signs or hind-end weakness, how does that change the risk picture?
• Should we check baseline blood work (including kidney values and BUN) before starting, since the field study showed a BUN signal?
• If we see increased drinking and urination, when is that an expected, monitor-at-home pattern versus a reason to come in?

When to call your veterinarian or an emergency clinic

Call the same day — or an emergency clinic if it is after hours — if your dog shows:

• Sudden loss of balance, stumbling, falling, or inability to stand or walk
• A first seizure, or more frequent seizures in a dog who already has them
• Rapid decline in mobility or mentation within days of an injection
• Persistent vomiting or diarrhea, especially with lethargy or not eating
• Signs you cannot explain and that worry you

You do not need to be certain the drug is the cause before calling. Veterinarians would much rather hear from you early. You or your veterinarian can report a suspected adverse event to the FDA at fda.gov/reportanimalae or by calling 1-888-FDA-VETS; reports are what make post-marketing surveillance work.

Sources

• FDA Center for Veterinary Management. Standard Adverse Event Pharmacovigilance Review for Librela (bedinvetmab injection), DPS-2024-141, September 2024. https://www.fda.gov/media/184483/download
• FDA. Animal Drug Safety-Related Labeling Changes — Librela (bedinvetmab injection), NADA 141-562, February 18, 2025. https://www.fda.gov/animal-veterinary/drug-labels/animal-drug-safety-related-labeling-changes
• AAHA. "Librela update: Changes to Librela label from Zoetis," February 5, 2025. https://www.aaha.org/trends-magazine/publications/librela-update-changes-to-librela-label-from-zoetis
• AAHA. "FDA publishes evaluation of adverse effects reported for canine OA treatment Librela," December 18, 2024. https://www.aaha.org/newstat/publications/fda-publishes-evaluation-of-adverse-effects-reported-for-canine-oa-treatment-librela
• UK Veterinary Medicines Directorate. Results of in-depth assessment of selected adverse events for Librela Solution for Injection for Dogs. https://www.gov.uk/government/publications/in-depth-assessment-of-selected-adverse-events-for-librela-solution-for-injection-for-dogs
• Zoetis. Librela (bedinvetmab injection) Prescribing Information, NADA 141-562. https://www.zoetisus.com/content/_assets/docs/vmips/package-inserts/librela-prescribing-information.pdf
• Farrell M, et al. Musculoskeletal adverse events in dogs receiving bedinvetmab (Librela). Frontiers in Veterinary Science, 2025. https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2025.1581490/full
• FDA CVM animal adverse-event database, public extract dated June 8, 2026; analysis by VetMedGuide (reports listing bedinvetmab as an active ingredient).