DELIVERY FORM: slow-release bolus for oral administration.

ACTIVE INGREDIENT(S): fenbendazole 12 g per bolus

CHEMICAL CLASS of the active ingredient(s): benzimidazole


between 100 and 300 kg at the day of administration

PARASITES CONTROLLED (spectrum of activity)

  • Gastrointestinal roundworms: Ostertagia spp, Trichostrongylus spp, Haemonchus spp, Cooperia spp and Oesophagostomum spp.
  • The intraruminal device aids in the control of parasitic bronchitis caused by Dictyocaulus viviparus.
  • The intraruminal device is effective in the treatment of established parasitic infections and continues to have a prophylactic effect up to 140 days after administration. This period may be reduced if cattle are moved to heavily infected pasture.


* Country-specific differences may apply: read the product label.

One capsule per animal weighing 100 to 300 kg.


  • LD50 (acute oral) in rats: >10000 mg/kg for fenbendazole a.i.

Suspected poisoning? Read the article on fenbendazole safety in this site.

Withholding periods (=withdrawal times) for meat & milk (country-specific differences may apply: read the product label)

  • Meat: UK 200 days
  • Milk for human consumption: Not for use in cattle producing milk for human consumption, or dairy heifers within 200 days of parturition.

WARNING !!!: Never use on humans, dogs or cats

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? YES, resistance of gastrointestinal roundworms to all benzimidazoles (incl. fenbendazole) in ruminants is a very serious and increasing problem worldwide, particularly in sheep and goats, but also in cattle. The most affected worm species in cattle are: Cooperia spp, Haemonchus spp, Ostertagia spp, Trichostrongylus spp, Oesophagostomum spp.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it can be due to resistance and not to incorrect use, which is usually the most frequent cause of product failure.

Alternative chemical classes/active ingredients to prevent resistance of gastrointestinal roundworms through product rotation:

These alternative products may not be available in all countries, or may not be available as drenches, or may not be effective against all the concerned parasites.

It is highly recommended to periodically check the resistance status of each property performing appropriate tests (e.g. fecal egg counts) under supervision of a veterinary doctor. Such tests are now routinely available for most producers in developed countries.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?

  • GENERIC (introduced in the 1970s)

*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: UK
GENERIC BRANDS available? Not many in the form of slow-release bolus so far.

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used drench or capsule brands for livestock click here.


PANACUR BOLUS is a slow-release device brand from MSD ANIMAL HEALTH with fenbendazole.

All benzimidazoles are veteran anthelmintics introduced in the 1970s (fenbendazole by HOECHST, now MSD = MERCK ANIMAL HEALTH). Fenbendazole has a broad-spectrum of activity against roundworms (gastrointestinal and pulmonary) & tapeworms, but is ineffective against flukes. Fenbendazole also kills eggs of roundworms (ovicidal activity). As all benzimidazolesfenbendazole has no efficacy whatsoever against external parasites (ticksflies, lice, mites, etc). Among the benzimidazoles fenbendazole is quite comparable with oxfendazole in terms of efficacy and safety. Fenbendazole is massively used worldwide in livestock and horses, much less in pets. It is not used in agriculture.

Click here for general information on good practices for the prevention and control of gastrointestinal worms in livestock.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.