Report lack of efficacy of a veterinary antiparasitic medicine

On Wednesday, 8 April 2026, Fimea participates in the Veterinary Medicine Safety Day. This year, the joint campaign between the European Medicines Agency, the Federation of Veterinarians of Europe (FVE) and national authorities focuses on the efficacy of antiparasitic medicines. The joint campaign reminds pet owners, animal keepers and vetenarians to use antiparasitics correctly and, when necessary, to report any lack of expected efficacy or other adverse events. The campaign day was first held in 2025.

The campaign can be seen across Fimea’s social media channels on LinkedIn and Instagram. Participate in the campaign by sharing the posts with people in your networks.

Always read the package leaflet completely

Lack of expected efficacy of antiparasitics can lead to health risks for both animals and humans. In order to maintain efficacy, it is important that antiparasitics are used correctly. Animals should only be medicated when necessary, and a veterinary diagnosis is often needed to select the correct treatment. The veterinarian weighs the benefits and risks not only to the animal, but also to the people and environment exposed to the medicine. Combination products should only be used in the case of a mixed infection or risk thereof, and their use should be strictly based on the indications of the combination product.

Before using the veterinary medicinal product, the owner or animal keeper must always read the package leaflet thoroughly and completely. The product must be used in accordance with the instructions of the veterinarian and the package leaflet, and the instructions in the package leaflet must also be followed when disposing of the product. After the treatment, observe whether the effect of the veterinary medicine is as expected.

When to suspect lack of expected efficacy?

The following signs may indicate a lack of expected efficacy of an antiparasitic medicine:

• There are signs of parasites in the animal, in its surroundings or in humans, regardless of the animal’s medication.
• The situation is not better after treatment, or it is only slightly better.
• The weight of the animal decreases or the animal grows poorly.
• Animal mortality on the farm is increasing.
• There is insufficient reduction of faecal egg count after treatment.

Why and how to report lack of expected efficacy?

In addition to the correct use of antiparasitics, it is important to report any lack of expected efficacy and other suspected adverse events. All reports are collected globally in an EU database, and, for example, signs of antiparasitic resistance to a veterinary medicine, can be monitored from the large mass of data. This will allow authorities to address the problems. 

The report can be submitted to either Fimea or the product marketer, whose contact details can be found in the package leaflet of the veterinary medicine. It is recommended to submit a report to Fimea via e-services, but a form that can be filled in manually or on the computer is also available on the website.

The report should include at least the following information:

• information on the animal: at least the species, and where possible, weight, age, sex and breed;
• name, dose used and date of administration of the veterinary medicinal product;
• in the case of antiparasitics, information on how the parasitic infection was diagnosed or confirmed;
• when the lack of expected efficacy or an adverse reaction was suspected and what the symptoms were;
• the results of examinations carried out after the suspicion.

More information:

Campaign page (EMA)

E-service