FOI release

FOI2026/00437 - Librela adverse events

Published 10 June 2026

1. Your request

May 2025 FOI Request ATI1067 pertained to the number of suspected adverse reactions for a particular drug against the number of doses used. In response, the Directorate stated “We can provide the reaction incidence, which is where the number of animals experiencing a suspected adverse event is divided by the estimated number of animals treated. The estimated number of animals treated is calculated from the number of doses sold by dividing the number of doses sold by the estimated average number of doses used per animal. For Librela, the figure we have previously used for the estimated average number of doses used per animal is 1. The resulting incidence has been rounded to 4 decimal places. The latest incidence of adverse events for Librela is 0.0015. This means that according to the data the VMD has received, fewer than 15 animals have experienced a suspected adverse event for every 10,000 doses of Librela used. This calculation does not consider any doses sold that were not used, for example doses discarded prior to administration.”

A more recent (16 February 2026) Press Release described the results of an in-depth assessment of selected adverse events for the same drug. In it, the Directorate stated that a new (1 December 2025) method of calculating adverse event frequency was used. It appears to be the same calculation that was used in May 2025, but the incidence differed slightly (1 to 10 animals per 1,000 estimated animals treated). Can you please provide the estimated average number of doses used per animal (or “dose factor”) that was employed in calculating the February 2026 incidence, as you did in response to the aforementioned May 2025 FOI Request?

2. Our reply

We hold the information you have requested. However, we are withholding it under Section 43(2) of the Freedom of Information Act 2000, because disclosure would be likely to prejudice the commercial interests of the product’s manufacturer.

The dose factor is a derived metric used to estimate the number of animals treated from the volume of doses sold. Although it appears to be a simple figure, disclosure of the exact value would enable reasonably accurate reverse‑engineering of commercially sensitive information that is not otherwise publicly available. Releasing the dose factor would allow third parties to calculate:

• the estimated number of animals currently receiving the product;
• retention and repeat‑treatment patterns; and
• month‑on‑month changes in product uptake and market position.

Because Librela is a chronic, repeat‑dose product, these calculations would closely approximate internal commercial intelligence relating to sales performance and customer behaviour. This information is not available through public regulatory documents or published safety data and is considered commercially sensitive within the competitive monoclonal antibody market.

For these reasons, we have concluded that disclosure of the dose factor would be likely to cause real and significant commercial prejudice to the manufacturer, and the exemption under Section 43(2) is engaged.

2.1 The Public Interest Test

As Section 43 is a qualified exemption, we have considered whether the public interest in disclosure outweighs the public interest in withholding the information.

• Factors in favour of disclosure: We recognise the public interest in transparency surrounding the assessment of adverse event data for veterinary medicines, and in understanding how incidence figures are calculated. There is a legitimate public interest in ensuring that the methodology used is robust, consistent, and subject to appropriate scrutiny.

• Factors in favour of withholding: The public interest in transparency is met through the information already published: the number of adverse event reports, the calculated incidence rate, and an explanation of how incidence is derived. Disclosure of the underlying proprietary denominator, the dose factor, would not meaningfully enhance public understanding of the product’s safety profile, because the incidence rate already reflects the outcome of the methodology.

Conversely, releasing the dose factor would be likely to cause commercial harm by revealing confidential usage patterns and commercially sensitive market information. Protecting such information supports a fair and competitive regulatory environment and aligns with the FOIA requirement to avoid causing undue commercial prejudice.

On balance, we have determined that the public interest in withholding the information outweighs the public interest in disclosure. We are therefore withholding the dose factor under Section 43(2) of the FOIA.