30 May 2025
Two leading vets clashed over the science of concerns about the impact of a major treatment for canine osteoarthritis as the issue dominated a vet conference.
Allister Webb
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Image © yobab / Adobe Stock
A scientific row has erupted over the effects of a major treatment for canine osteoarthritis following public calls for a ban on its use.
A new study has claimed musculoskeletal adverse event reports (MSAERs) were recorded nine times more frequently in dogs treated with Librela than with other drugs.
However, a prominent vet associated with the treatment has insisted it is still too early to understand the potential scale of the problem.
The division was highlighted during heated exchanges at the Veterinary Osteoarthritis Congress (VOACON) in Loughborough last week.
A recent paper co-authored by senior figures from the drug’s manufacturer, Zoetis, had argued that reported adverse events from the use of Librela were considered to be either rare or very rare. But the latest analysis, published in the journal Frontiers of Veterinary Science, said 90 per cent of MSAERs reported between May 2021 and December 2024 which did not have conflicting neurological or systemic diagnoses were attributed to Librela.
The paper, which drew on data from the European Medicines Agency’s EudraVigilance database plus 19 individual cases, reported there were nine times as many reported cases of ligament or tendon injury, polyarthritis, fracture, musculoskeletal neoplasia and septic arthritis within Librela-treated dogs than in others treated with one of five comparator medications.
The number of MSAERs attributed to Librela in less than four years was also found to be three-fold higher than the total attributed to all comparator drugs over a 20-year period.
Lead author Mike Farrell accused Zoetis of seeking to “deny, deflect blame and downplay” the impact of Librela during his 21 May presentation, including suggestions that the company had not classed incidents as seriously as reporting clinicians had – a claim the firm rejects.
Mr Farrell urged vets to be specific when reporting incidents, adding: “I’ve just told you there is something wrong. But what happens next isn’t up to me. It’s up to you.”
However, Zoetis officials have insisted they actively encourage the reporting of adverse events either directly to themselves or the VMD, and that they take all such reports seriously and follow all their legal obligations.
Meanwhile, a separate study published in the same journal and also presented at VOACON, found bedinvetmab – the monoclonal antibody sold under the Librela brand name – was associated with only four adverse events among 52 dogs treated with it across an eight-week period, compared to 17 among 49 dogs which had meloxicam administered over the same timescale.
Its corresponding author, John Innes, told delegates there was also a larger mean reduction in Canine Orthopaedic Index scores linked to bedinvetmab than meloxicam, though that was not considered statistically significant.
Later, while speaking from the floor, he congratulated Mr Farrell for starting a debate on Librela, but questioned both the lack of a control group in the latest study and the quality of the evidence presented in what he described as “case reports”.
Mr Farrell said: “These are not just 19 cases. These are people’s pets.”
But while he acknowledged he had worked as a consultant for Zoetis, Prof Innes insisted he was not currently being paid by the company and was giving his “professional opinion” on the science.
He added: “Nobody wants adverse events with drugs, but adverse events occur with nearly every drug I can think of.
“It’s a matter of the risk versus the benefit, and we don’t know what the scale of it is. That’s all I’m saying.”
A subsequent statement from Zoetis said it remained confident of the evidence for Librela’s safety and efficacy, and was taking comprehensive steps to investigate what it described as a very small number of accelerated joint destruction cases.
It added that adverse events can be reported directly to the company by telephoning 0345 300 8034 or emailing [email protected]
The row follows both a warning from regulators to American vets late last year and a more recent online petition demanding a ban on the use of Librela in the UK.
Although the VMD has said it will take action over the drug if it feels that is necessary, the congress was told its online reporting portal was out of action.
