What are Adverse Drug Events?

An adverse Drug Event (ADE) is defined as any observation that occurs after any use of a veterinary medicinal product, whether or not considered to be product related, that is unfavourable and unintended. ADEs may include effects on the patient, humans handling the products or patient, or the environment. Lack of efficacy events are also ADEs.

Who manages Adverse Drug Event reports and who can report them?

The Veterinary Medicines Directorate (VMD) and Marketing Authorization Holder (MAH; pharmaceutical company) work together to collate information about, identify and mitigate risks associated with veterinary pharmaceuticals. These processes rely on spontaneous reporting of ADEs. Anyone can report an ADE, including veterinary professionals, owners and other interested parties. Under the RCVS Code of Professional Conduct, veterinary surgeons and veterinary nurses are professionally required to report ADEs.

Why is reporting Adverse Drug Events important?

Prior to receiving a marketing authorization (licence), veterinary medicines undergo a significant amount of testing and evaluation. During this phase many of the more common ADEs associated with a medicine will be identified. However, pre-marketing testing cannot hope to identify all possible ADEs that will occur once a product is in widespread clinical use in a diverse population of animals or for ‘off-label’ use. In addition, products without an authorization do not undergo such testing.

Not all ADEs are true adverse drug reactions (ADRs). ADE reports are collated and analysed to identify statistically associated drug–event combinations. Reported cases are also reviewed to determine whether a causal relationship is likely based on pharmacology. As the identification of true ADRs relies on statistical analysis, higher reporting rates allow the VMD to identify and mitigate any potential harm caused by a particular drug more quickly. A further benefit is that reporting both previously known and previously unknown ADEs makes it feasible to more accurately estimate the incidence of ADRs in particular species, breeds, diseases and combinations of drugs.

How to report an Adverse Drug Event?

ADEs can be reported to the VMD or the MAH (for authorized products); these organizations share ADE information so there is no need to report to both. Reports to the VMD can be made via a dedicated webpage (www.gov.uk/report-veterinary-medicine-problem). This platform is under review and a new system should be put in place during 2026. Reporting via the MAH is recommended where possible. If an ADE is noted after an animal has been given a human medicine or a medicine that is not approved for use in animals, the VMD pharmacovigilance team should be contacted by email at [email protected] or by telephone on 01932 336911.

Where can I get more information about Adverse Drug Events?

The Summary of Product Characteristics (datasheet) for a product provides information on the known risks for authorized products. The VMD Product Information Database (www.vmd.defra.gov.uk/productinformationdatabase/) contains the most up-to-date version of this information. Formularies include information about known adverse events for products without an MA.