Brand: NITROMEC ® Injection

Company: VIRBAC

FORMULATION: «injectable» to be administered subcutaneously under the loose skin in front of, or behind the shoulder in cattle.


CHEMICAL CLASSES of the active ingredient(s):

  • Ivermectin: Macrocyclic lactone
  • Clorsulon: Benzenesulphonamide
  • Nitroxynil: halogenated phenol


PARASITES CONTROLLED* (spectrum of activity)

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


*Can be slightly different in some countries: read the product label!


  • LD50 (acute oral) in rats:
    • ivermectin a.i. 2-3 mg/kg (according to MSDS)
    • closulon a.i. >10000 mg/kg (according to MSDS)
    • nitroxynil a.i. 170-450 mg/kg (for various salts)
  • LD50 (acute dermal) in rats:
    • ivermectin a.i.  >660 mg/kg (according to MSDS)
    • clorsulon a.i. n.a.
    • nitroxynil a.i. n.a.
  • Estimated hazard class according to the WHO: not applicable for veterinary medicines

Suspected poisoning? Read the articles on ivermectin safety, clorsulon safety and nitroxinil safety in this site.

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

  • Meat: 56 days (ESI = 120 days).
  • Milk: Do not use in female animals which are producing or may in the future produce milk or milk products for human consumption

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, in gastrointestinal roundworms in cattle, particularly in: Cooperia spp, Haemonchus spp, Oesophagostomum spp, Ostertagia spp, Trichuris spp

Resistance of gastrointestinal roundworms to ivermectin in sheep, goats and cattle has been reported almost worldwide, including the USA, UK, Australia and New Zealand. Based on the very abundant and frequent use of ivermectin and other macrocyclic lactones (with cross-resistance to ivermectin) in livestock it must be assumed that resistance of these roundworms to this chemical class will continue spreading and strengthening in the future. The nitroxynil in the formulation may control some worm species resistance to ivermectin

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it may 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 injectables.

There are a few reports on liver fluke (Fasciola hepatica) resistance to clorsulon in sheep, but so far it is not such an extended problem as for gastrointestinal roundworms. To our knowledge there are no published reports on resistance of liver fluke (Fasciola hepatica) to clorsulon in cattle.

Learn more about resistance and how it develops.


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


*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 product is marketed (maybe under another TM) Australia, New Zealand (under the tradename COMBAT NITROMEC INJECTION)
GENERIC BRANDS available? YES, perhaps not with the same composition.

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

For an overview on the most used antiparasitic injectable brands for livestock click here.


NITROMEC INJECTION for Cattle from VIRBAC is a rather unusual combination of generic ivermectin, clorsulon, and nitroxynil.

Ivermectin is a broad spectrum parasiticide with efficacy against internal parasites (mainly roundworms) and against external parasites as well (mainly mites, lice, grubs, etc). This is why it is called an endectocide (controls endoparasites and ectoparasites). Ivermectin was the first macrocyclic lactone discovered and introduced in the 1980s by MS&D AgVet. It is the parasiticide for livestock and pets most widely used worldwide, with probably thousands of generic brands. Ivermectin is probably the best veterinary parasiticide ever developed, highly effective against roundworms as well as against numerous external parasites (ticksflies, lice, mites, etc.). As all macrocyclic lactonesivermectin used alone is ineffective against tapeworms and flukes, regardless of the delivery form. It is massively used in livestock and horses, less in pets. It is also used in agriculture and against household pests.

Clorsulon is a veteran flukicide introduced in the 1970s (by MS&D-AGVET), a benzenesulphonamide with a narrow spectrum of efficacy against a few trematode species. It has no efficacy whatsoever on roundworms (gastrointestinal, pulmonary, ocular, etc.) or tapeworms, nor on external parasites of cattle (mites, lice, ticks, grubs, etc). It is moderately used in cattle, not at all in sheep, goats, horses, swine, poultry or pets. It is not used in agriculture.

Nitroxynil is a narrow spectrum anthelmintic, introduced in the 1960s (by MAY & BAKER). It is effective against liver flukes and a few gastrointestinal  roundworms (e.g. Haemonchus spp, Bunostomum phlebotomum and Oesophagostomum radiatum). But it provides no control of numerous other gastrointestinal roundworm species that usually infect ruminants together with the mentioned species, and is completely ineffective against external parasites. It is scarcely used in ruminants, not at all horses, swine, poultry or pets. It is not used in agriculture.

The reason for combining clorsulon and/or nytroxynil with ivermectin is adding efficacy against liver flukes (Fasciola hepatica), because ivermectin is not effective against any fluke species. Nitroxynil may also control some gastrointestinal worm species already resistant to ivermectin.

All 1% ivermectin injectables used on cattle at the recommended dose of 200 mcg/kg offer a rather poor control of cattle ticks Boophilus (=Rhipicephalus) microplus (a frequent pest in Australia) usually insufficient for most producers.

Being one of the best antiparasitics ever developed, ivermectin does not control all parasites of livestock. Unfortunately advertising and even the label of some generic formulations in less developed countries often include unsubstantiated claims. To help preventing confusion and misuse it is useful to know that whatever ivermectin 1% + clorsulon 10% injectable formulation administered at the usual recommended dose of 1 ml/50 kg bw DOES NOT CONTROL:


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.