Prescribers and users of closantel-containing products are reminded to ensure accuracy of dosing in order to avoid residue violations in treated animals

Notice type: Advisory

Date: 04/04/2024

The HPRA monitors reports of adverse events to veterinary medicinal products as part of our role in the post-authorisation safety monitoring of veterinary medicinal products in Ireland. The HPRA has become aware of a limited number of reports where residues of closantel above the Maximum Residue Limit (MRL) have been detected post slaughter from treated livestock, which could indicate that the dose of product administered is higher than that which has been approved, resulting in the stated withdrawal period being insufficient. 

Product name or type:
Closantel-containing veterinary medicines indicated for sheep and cattle, whether as a single active substance or present in combination with other active substances.

Active Substance:

Product Classification:

Anthelmintics (flukicide wormers)

Manufacturer Or Supplier:


Authorisation Holder:


Prescription Required:

Target Audience:

Veterinary practitioners, Veterinary nurses, Licensed retailers, farmers

Problem Or Issue:
To ensure the safety of consumers of food and food products derived from animals treated with veterinary medicines containing closantel, the European Commission has set maximum residue limits (MRLs) for closantel in the edible tissues of animals. In order for closantel-derived residues to deplete below the MRLs, a sufficient time (withdrawal period) between treatment and slaughter must be observed and which takes into account the dose rate and route of administration approved for the concerned products. Closantel has slow and limited metabolism and it takes a relatively long time for it to be eliminated from tissues. Unless care is taken to accurately assess the bodyweight of animals to be treated, they can be over-dosed, leading to residues in excess of the MRL being present at time of slaughter. 

The risk of overdosing increases when the bodyweight of animals to be treated is not accurately assessed, or when animals are grouped for dosing but the range of individual bodyweights within the group differs significantly, resulting in lighter-weight animals receiving a higher than recommended dose. The risk is further increased where users dose to a standard bodyweight, irrespective of whether there are mixed weights of animals in the group. 

Background Information Or Related Documents:

In 2019, following a referral procedure, the European Medicines Agency increased the withdrawal period for meat and offal in sheep following treatment with injectable veterinary medicinal products which contain closantel as a single active substance. In that case, the withdrawal periods of the products concerned were increased to 107 days. This procedure did not apply to non-injectable closantel containing medicines, nor to those medicines containing closantel in combination with another substance. Withdrawal periods are set by the HPRA on the basis of residue depletion studies submitted with applications for marketing authorisations and are usually specific to each formulation and product. There are 12 veterinary medicines containing closantel currently authorised in Ireland. Based on the available evidence from adverse event reports concerning residue violations and the follow-up investigations conducted by marketing authorisation holders (MAH) of concerned products, the currently approved withdrawal periods are, at present, considered to remain appropriate provided that the concerned medicines are used correctly i.e. dosed in accordance with the dose rate approved in the Summary of Product Characteristics (SPC). However, the HPRA in cooperation with MAHs will continue to closely monitor for reports of residue violations.

Actions To Be Taken:

To ensure administration of the correct dose, bodyweight should be determined as accurately as possible before dosing.

Accuracy of any dosing device should be checked.

If animals are to be treated collectively rather than individually, they should be grouped according to their bodyweight and dosed accordingly in order to avoid over-dosing.

Do not exceed the recommended dose.

Respect the withdrawal period of the product to be administered as this will differ between products.

Always read the label and package leaflet before use.

For advice on the use of veterinary medicines and on parasite control in general, consult your veterinary practitioner.


All suspected adverse events, including reports of residue violations should be reported immediately, preferably to the marketing authorisation holder, or alternatively to the HPRA.

Further Information:

All antiparasitic veterinary medicines for food-producing animals were upregulated to supply under veterinary prescription in 2021.

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