Mebendazole is a broad-spectrum antiparasitic active ingredient used in veterinary medicine in pets and livestock against internal parasites (roundworms, tapeworms). It is not used against agricultural and household pests. It belongs to the chemical class of the benzimidazoles.

Common name:  MEBENDAZOLE

Type: veterinary medecine
Chemical class: benzimidazole


Molecular structure of MEBENDAZOLE 


Type of action: broad-spectrum nematicide and taenicide anthelmintic, endoparasiticide
Main veterinary parasites controlled: gastrointestinal and respiratory roundworms (= nematodes) and tapeworms

Efficacy against a specific parasite depends on the delivery form and on the dose administered.

Click here for general information on features and characteristics of PARASITICIDES.


Click here to view the article in this site with the most common dosing recommendations for mebendazole used in domestic animals.


Oral LD50, rat, acute*: 714-1434 mg/kg
Dermal LD50, rat, acute*: not found
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.

MRL (maximum residue limit) established for either beef, mutton pork or chicken meat*:

  • CODEX: No
  • EU: Yes
  • USA: No
  • AUS: Yes

* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock.

Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.

Learn more about mebendazole safety (poisoning, intoxication, overdose, antidote, symptoms, etc.).

General information on the safety of veterinary antiparasitics is available in specific articles in this site (click to visit):


Never use products for livestock on dogs and cats unless they are explicitly approved for both livestock and pets. Pets may not tolerate livestock formulations

It is obvious that veterinary products are not intended for and should never be used on humans!!!


Decade of introduction: 1970
Introduced by: JANSSEN
Some original brands: OVITELMIN, SUPAVERM
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, scarce
Use in HORSES: Yes, moderate
Use in DOGS and CATS: Yes, scarce
Main delivery forms: 

Use in human medicine: Yes
Use in public/domestic hygiene: No
Use in agriculture: No
Generics available:  Yes


In livestock & horses: Yes, as all benzimidazoles, very frequent worldwide in gastrointestinal roundworms in sheep, goats and cattle.
In dogs and cats: No

Visit also the section in this site about parasite resistance to antiparasitics and more specifically to mebendazole.


Mebendazole is a veteran anthelmintic (wormer) compound belonging to the chemical class of the benzimidazoles. Mebendazole is moderately used in pigs, dogs ans cats. It is very scarcely used in ruminants. It is vastly used in horses.

For pets it is very often used in combinations that broaden the spectrum of activity, mostly a taenicide (e.g. praziquantel).

Mebendazole was the first benzimidazole approved for use on humans.

Efficacy of mebendazole

Mebendazole has a broad-spectrum of activity against gastrointestinal roundworms and lungworms of livestock, including adults and L4-larvae of the most important species (e.g. of the genus Bunostomum, Haemonchus, Ostertagia - Teladorsagia, Trichostrongylus, Cooperia, Nematodirus, Chabertia, Oesophagostomum, Trichuris, Dictyocaulus, Muellerius, etc.) as well as arrested larvae of several species. It is also effective against most livestock tapeworms (e.g. Moniezia, Taenia).

In horses it controls the major parasitic roundworms such as Large Strongyles (Cyathostomins), Small Strongyles (Strongylus spp), Parascaris equorum, etc. as well as tapeworms. (e.g. Anaplocephala spp).

It is also effective against the major parasitic roundworms (e.g. Ancylostoma, Toxocara, Trichuris, Uncinaria) and tapeworms (e.g. Echinococcus, Dipylidium, Taenia, etc.) of dogs and cats.

Mebendazole is absorbed slowly in the stomach. Therefore the longer it remains there, the better the efficacy. In carnivores (e.g. dogs and cats) and other animals with a simple stomach the passage through the stomach is rather fast and therefore a higher dosage or repeated treatments are usually required.

Mebendazole has no residual effect. This means that a single administration will kill the parasites present in the host at the time of treatment, but it will not protect against re-infestations.

At the therapeutic dose mebendazole is not effective against flukes and whatsoever external parasites.

Resistance of worms to benzimidazoles, including mebendazole in dogs, cats, pig and poultry is not a problem so far. However resistance of several gastrointestinal roundworms to all benzimidazoles, including mebendazole is already very high and very frequent worldwide in sheep and goats, slightly lower in cattle. For this reason, the risk that benzimidazoles fail to protect ruminants against gastrointestinal roundworms is considerable worldwide.

Pharmacokinetics of mebendazole

Mebendazole is very poorly soluble in water. Orally administered mebendazole is poorly absorbed into the bloodstream: ~30% in pigs, and <10% in dogs. This means that significant amounts remain in the gastrointestinal tract and are available for the control of gut dwelling roundworms and tapeworms.

Absorbed mebendazole is quickly broken down in the liver to metabolites without anthelmintic efficacy. Both the parent molecule and its metabolites are excreted mainly through bile and feces, the rest through urine. However, there are important species-specific differences. Whereas in dogs >90% of the administered dose is excreted through feces, up to 50% is excreted through urine in swine.

Influence of parasites. Heavy liver fluke infestations in sheep slow down the metabolism of mebendazole in the liver, which increases its bioavailability and prolongs the residence time. This may require longer withholding periods.

Mechanism of action of mebendazole

The molecular mode of action of all benzimidazoles, including mebendazole, consists in binding to tubulin, a structural protein of microtubules. These microtubules are important organelles involved in the motility, the division and the secretion processes of cells in all living organisms. In the worms the blocking of microtubules perturbs the uptake of glucose, which eventually empties the glycogen reserves. This blocks the whole energy management mechanism of the worms that are paralyzed and die or are expelled.

Since cell division is also disturbed, worm egg production and development is also blocked by benzimidazoles, i.e. most of them also have an ovicidal effect.

Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.