Brand: CLOSAMECTIN Injection


FORMULATION: «injectable». To be injected subcutaneously into the neck. A maximum dose of 10ml should be administered at any one site with any residual volume administered at another site in the neck.


CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED* (spectrum of activity)

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


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


  • LD50 (acute oral) in rats:
    • ivermectin: a.i. 50 mg/kg (according to MSDS)
    • closantel: a.i. >5000 mg/kg (according to MSDS)
  • LD50 (acute dermal) in rats:
    • ivermectin: a.i. 342 mg/kg (according to MSDS)
    • closantel: n.a.
  • Estimated hazard class according to the WHO: not applicable for veterinary medicines

Suspected poisoning? Read the articles on ivermectin safety and closantel safety in this site.

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

  • Meat: UK + EU countries cattle: 49 days; sheep: 28 days
  • Milk for human consumption: UK + EU countries: Not authorised for use in animals producing milk 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?

Risk of resistance? YES, considerable in gastrointestinal roundworms in sheep (very high) and cattle (high) particularly in:

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.

There are reports on resistance of gastrointestinal roundworms to closantel in sheep, but to our konwledge not in cattle. It can be assumed that the closantel in this formulation may contribute to overcome potential resistance of roundworms to ivermectin.

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

Cases of resistance of liver flukes to closantel have been reported in sheep, but so far not in cattle. They seem to remain isolated cases, nothing comparable with the extension and prevalence of resistance in gastrointestinal roundworms. 

Alternative chemical classes/active ingredients to prevent resistance of liver flukes through product rotation:

These alternative products may not be available in all countries, or may not be available as injectables.

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 brand/product is marketed: UK, Ireland + other EU countries, New Zealand
GENERIC BRANDS available? Not many in most countries, in this particular composition.

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

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


CLOSAMECTIN Injection for Cattle & Sheep from NORBROOK is an injectable formulation containing generic ivermectin and closantel

Ivermectin was the first macrocyclic lactone introduced in the market in the early 1980s (by MSD AGVET, later MERIAL). It was a milestone and a tremendous progress that revolutionized the control of veterinary parasites. It is used massively in livestock and pets, and also in agricultural pesticides. Nowadays there are thousands of brands with generic ivermectin worldwide.  It is effective against most species of roundworms that affect cattle and against many external parasites (mainly lice, mites, buffalo flies, etc.), but not against tapeworms or flukes.

Closantel is a veteran salicylanilide anthelmintic introduced in the 1970s (by JANSSEN). It is moderately used in livestock, but neither in pets nor in agriculture. It is highly effective against adult and immature (>8 weeks old) liver flukes (Fasciola hepatica, Fasciola gigantica) and against several important gastrointestinal roundworms (e.g. Bunostomum, Haemonchus, OesophagostomumOstertagia - Teladorsagia, Strongyloides, Trichostrongylus). It has no efficacy against lungworms (Dictyocaulus viviparus), eyeworms (Thelazia spp) lungworms, lice or mites.

The combination of both compounds makes sense because it extends the spectrum of activity of both active ingredients, and closantel may control ivermectin-resistant roundworms if present in the population.

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 injectable used at the recommended dose of 200 mcg/kg even in combination with closantel DOES NOT CONTROL:

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.