Librela Side Effects: What the FDA Has Actually Said

What are the side effects of Librela in dogs?

Librela’s US label lists neurological, urinary, digestive, general and muscle or joint signs reported after approval, and says death, including euthanasia, has been reported in some cases.

Librela (bedinvetmab) is a monthly injection for pain from osteoarthritis in dogs. FDA approved it on May 5, 2023. Everything below comes from FDA, the UK and EU regulators and published papers, checked on 2026-10-27.

Call a vet now if your dog cannot stand, collapses, has a seizure, drags a back leg or loses control of urine suddenly. These are signs the FDA letter and label name. A spinal problem can cause the same signs (see back legs giving out in an old dog), and a vet can tell which it is.

The US label’s post-approval list, as revised in February 2025:

• Neurological: ataxia (wobbly, uncoordinated walking), seizures, paresis (partial weakness), proprioception deficits, paralysis
• General: anorexia, lethargy, recumbency (unable to get up)
• Urinary: increased thirst and urination, urinary incontinence
• Digestive: vomiting, diarrhea
• Muscle and joint: muscle weakness, tremors, lameness

What has the FDA actually said about Librela, and when?

FDA has acted on Librela in several dated steps since 2023, and its Center for Veterinary Medicine says it cannot order safety label changes by itself.

Date	Who	What happened
May 5, 2023	FDA	Librela approved for dogs.
Dec 16, 2024	FDA	Dear Veterinarian letter names ataxia, seizures, other neurologic signs (paresis, recumbency, urinary incontinence), polyuria and polydipsia. Some reports list death or euthanasia.
Feb 18, 2025	FDA	Label gains a post-approval adverse reaction list and a Client Information Sheet. Vets must discuss it with owners before each injection.
Oct 27, 2025	FDA	Report listing released: 15,123 dog reports from May 5, 2023 to Sept 30, 2025.
Nov 4-6, 2025	EMA (EU)	Veterinary committee backs adding diarrhea and vomiting as rare events, and immune-mediated polyarthritis, paresis, paralysis and seizure as very rare events.
Feb 16, 2026	UK VMD	In-depth assessment: benefit-risk still positive, no label change announced at that point, monitoring continues.
May 26, 2026	UK VMD	Label update adds joint swelling, joint pain, bone and joint disorder and soft tissue ossification as very rare events. For a dog with new or worse joint signs after a dose, the label advises considering more diagnostics and stopping treatment case by case.
Jul 14, 2026	FDA	Report listing released: 17,779 dog reports from May 5, 2023 to June 30, 2026. Same limits: no incidence, no proof of cause.

The December 2024 letter states that FDA “does not currently have the authority to mandate safety-related labeling changes.” The February 2025 change is a label revision, which is a separate event from any earlier company announcement.

What do the 17,779 reports mean?

FDA’s latest listing counts 17,779 spontaneous dog reports in 38 months (15,123 of them by September 2025), and FDA states the total cannot be used to calculate how often side effects happen.

FDA’s own cover note gives the reason: “there is no accurate way to determine how many animals were actually given the drug, which is needed as the denominator in calculations of incidence and relative risk.” Without the number of dogs treated, 17,779 cannot become a percentage.

The same note lists more limits. A report does not prove the drug caused the event. The illness, other drugs or something else may have. Reporting is voluntary, so underreporting is common. And reporting “may be greater when the drug is newly marketed, or when media publicity occurs.” FDA also says one report can list several signs, so the sign counts below do not add up to the report total.

The October 2025 listing covered 15,243 reports across all species: 15,123 in dogs, 5 in cats, 3 in other species and 112 in people with accidental exposure.

Which signs are reported most, and are they on the label?

In FDA’s listings, the most-reported signs in dogs given the injection under the skin are lethargy, euthanasia, thirst, urination and ataxia, and nearly all appear on the current label.

Counts are the number of times a sign was reported, not dogs. The first listing covers May 5, 2023 to March 31, 2024. The second covers May 5, 2023 to Sept 30, 2025.

Sign (FDA wording)	To Mar 2024	To Sep 2025	On US label list?
Lethargy	404	1,640	Yes
Death by euthanasia	234	1,690	Death and euthanasia noted as outcomes
Polydipsia (thirst)	373	1,297	Yes
Polyuria (urination)	359	1,221	Yes
Ataxia	232	1,184	Yes
Vomiting	316	1,152	Yes
Seizure	198	1,111	Yes
Diarrhea	299	1,076	Yes
Urinary incontinence	237	1,036	Yes
Limb weakness	127	809	Yes (muscle weakness)

Two things stand out. First, counts grew about 3.4 to 7.2 times while the window grew from 11 to 29 months. Growth in reports can reflect more dogs treated, more attention after the 2024 and 2025 FDA actions, or both. FDA’s note says publicity raises reporting, so this table cannot say the drug got riskier.

Second, the listing also holds many entries that match the debate about joints and walking, such as hind limb paresis (501), unable to walk (599) and knuckling (298) in the 2025 data. Those entries are in the FDA data, but FDA does not say they are caused by Librela.

Is Librela safe for dogs?

Regulators in the US and UK still allow Librela, and the UK regulator says it is “confident that the overall benefit-risk balance of the product remains positive,” but serious reports are real and cause is often unclear.

The UK Veterinary Medicines Directorate published its in-depth assessment on February 16, 2026. It estimated the following per animals treated, from UK data:

• Death: rare (1 to 10 per 10,000)
• Faster-than-expected osteoarthritis progression: very rare (under 1 per 10,000)
• Lack of efficacy: rare (1 to 10 per 10,000)
• All adverse events: uncommon (1 to 10 per 1,000)

The VMD said a small subset of dogs aged 6 or older may deteriorate within 14 days, and that it is “currently unclear whether many of these reports are product related.” It announced no label change and agreed with Zoetis to monitor reports. These are estimates per animals treated, which FDA’s US report listing cannot give. They still depend on how many cases get reported.

What did the pivotal field studies measure?

The two 84-day masked field studies in the US label compared Librela with saline in 553 dogs and mainly recorded infections, skin findings and lab changes.

• US study: 272 dogs (135 Librela, 137 saline), up to three injections 28 days apart. Urinary tract infection occurred in 15 Librela dogs (11.1%) and 11 saline dogs (8.0%). Inappropriate urination was 4 (3.0%) versus 1 (0.7%).
• European study: 281 dogs (138 Librela, 143 saline). Increased blood urea nitrogen was found in 19 (13.8%) versus 7 (4.9%). Lethargy was 5 (3.6%) versus 0. Two Librela dogs had serious events and were euthanized: a 13-year-old Bichon Frise with worsening heart failure and kidney failure, and an 8-year-old mixed-breed dog with pancreatitis.

What these studies did not test: 84 days is about three injections, so they cannot show what happens after a year of monthly doses. About 270 dogs per study is too small to detect events as rare as 1 in 1,000. That gap is why post-approval reports matter, and also why they are hard to read.

What is the Librela controversy?

The Librela controversy is a disagreement over whether reported deaths, collapses and fast joint damage are caused by the drug, with no controlled study yet settling it.

Three published signals matter, each with limits:

• A June 2026 paper by von Pfeil and colleagues argues that nerve growth factor blockade may mask early joint deterioration and cause rapidly progressive osteoarthritis, as seen with human drugs of that type. It is an expert review, and the authors call these events “purportedly rare.”
• At a May 2025 conference, Mike Farrell presented an analysis of EU reporting data and 19 cases. Vet Times reported critics, including John Innes, who questioned the lack of a control group. Zoetis said it remains confident in Librela’s safety and efficacy.
• Innes and colleagues, also reported by Vet Times, found 4 adverse events in 52 dogs on bedinvetmab versus 17 in 49 on meloxicam over eight weeks.

How long do Librela side effects last, and what about long term?

No source gives a typical duration or a long-term rate for Librela side effects.

The controlled osteoarthritis field trials lasted 84 days. The label also describes a six-month controlled safety study in healthy Beagles and an uncontrolled six-month continuation in 89 dogs. FDA’s report listings do not include outcomes. The VMD noted early deterioration within 14 days in a subset of older dogs, which means the timing can be quick. Report data cannot show whether a sign resolved.

If a sign appears after an injection, get it seen by a vet. Record when the shot was given, the date the sign began and a short phone video.

What should I ask my vet before the next injection?

Ask your vet the questions that the Client Information Sheet and the field data leave open, because the label requires the vet to discuss that sheet with you before each injection.

1. What is my dog’s pain and mobility baseline today, and how will we measure change?
2. Which of my dog’s other conditions or drugs raise risk, and has anything changed since the last dose?
3. Should we image the joints before starting or at set intervals, as the 2026 review suggests?
4. Which signs mean a same-day call, and which can wait for a recheck?
5. If my dog worsens after a dose, who do I call after hours?
6. What are the alternatives if we pause? Your vet can lay out options such as other arthritis treatments.
7. Will you report any event to FDA at www.fda.gov/reportanimalae, or should I?

Older dogs have more of the conditions that mimic these signs, so also see when a dog counts as a senior, signs of arthritis and seizures in elderly dogs. For the drug itself, read Librela for dogs. More pain and mobility pages are in the guides index.