Thiophanate is an antiparasitic active ingredient used in veterinary medicine in livestock against internal parasites (roundworms). It is not used against agricultural and household pests. It belongs to the chemical class of the pro-benzimidazoles.

Common name: TIOPHANATE

Type: veterinary medecine
Chemical class: pro-benzimidazole


Molecular structure of THIOPHANATE 


Type of action: broad-spectrum nematicide anthelmintic, endoparasiticide
Main veterinary parasites controlled: mainly gastrointestinal roundworms (= nematodes).

Efficacy against a specific parasite depends on the delivery form and on the dose administered. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasite. Check the labels of the products available in your country.

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


Oral LD50, rat, acute*: >15000 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: No
  • USA: No
  • AUS: No

* In the form of albandazole solfoxide and sulfone. 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.

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: MAY AND BAKER → MERIAL
Some original brands: NEMAFAX
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, but almost completely replaced by newer anthelmintics
Use in DOGS and CATS: ?
Main delivery forms: 

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


In livestock: Yes, as all benzimidazoles, very frequent worldwide in gastrointestinal roundworms in sheep, goats and cattle.

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


Thiophanate is a veteran pro-benzimidazole. It is transformed into an anthelmintic benzimidazole in the stomach and the intestine of the host, shortly after ingestion. .

It is available mainly in the form of drenches for cattle, sheep, goats and pig but has been vastly abandoned for use in livestock or pets.

Thiophanate was used in agriculture as a fungicide.

Efficacy of thiophanate

Thiophanate itself has no anthelmintic properties. Therefore its efficacy depends on its successful transformation to the corresponding benzimidazole (ethyl benzimidazol-1H-yl-2-carbamate).

Thiophanate is effective against the most relevant gastrointestinal roundworms of ruminants and pigs (e.g. of the genus Bunostomum, Haemonchus, Ostertagia - Teladorsagia, Trichostrongylus, Cooperia, Nematodirus, Chabertia, Oesophagostomum, Trichuris, etc.), both as adults and larvae. Depending on the dose it is also effective against arrested larvae of certain species, and against some lungworms.

Thiophanate is not effective against tapeworms (cestodes) or flukes (trematodes).

Thiophanate has no residual effect. This means that a single administration will kill the parasites present in the host at the time of treatment and protect against re-infestations for a few days, but not for weeks.

Unfortunately, resistance of several gastrointestinal roundworms to all benzimidazoles, including the benzimidazolic metabolite of thiophanate 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 thiophanate

Following oral administration thiophanate and its benzimidaziolic metabolite are detectable in plasma for 60 to 72 hours. In cattle and goats the biotransformation of thiophanate to its anthelmintic metabolite is > 50%, in sheep is is <35%. Highest plasma levels are reached between 8 and 15 hours after administration. Transformation of thiophanate into its anthelmintic metabolite is achieved in the tissues (liver and kidneys) but also in the ruminal fluid.

Mechanism of action of thiophanate

Thiophanate acts on the worms only after transformation to its benzimidazolic metabolite. The molecular mode of action of all benzimidazoles 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.