Veterinary medicinal products shall be granted a marketing authorisation only if the evaluation of the data on their quality, safety and efficacy leads to the conclusion that the benefit associated with their use outweighs the risks involved. Clinical trials carried out as part of an application for a marketing authorisation (MA) identify a number of adverse events likely to occur as a result of the use of a medicinal product. However, since these trials are carried out on a limited number of animals and under standardised conditions of use, the use of the medicinal product on a large scale and under real-life conditions on the ground, once it has been authorised, makes it possible to specify the adverse events of that medicinal product and to identify potential risk factors (species, race, age, pre-existing conditions, etc.). 

The purpose of pharmacovigilance is thus to detect as soon as possible any emerging signal, whether it is an unexpected adverse reaction, or a known adverse reaction but whose frequency or severity is unexpected. That post-MA monitoring makes it possible, where appropriate, to adapt the risk management measures which may range from the addition of a precaution of use to the package leaflet, to the withdrawal of the marketing authorisation. 

The monitoring of adverse reactions to veterinary medicinal products is carried out through the veterinary pharmacovigilance system, which has been fully operational since 2002. The effectiveness of the scheme is based on spontaneous declarations, which are now sent in more than 90 % of cases by veterinarians. These declarations are then recorded and assessed both by the marketing authorisation holders concerned and by the institutional actors Anses-ANMV and the Centre for Veterinary Pharmacovigilance in Lyon (CPVL). The potential signals thus identified are then subject to a collective assessment. This evaluation may be carried out at European level with experts from the competent authorities of the other European States and/or at national level, with experts from the Veterinary Medicinal Products Monitoring Committee (CSMV).