Company: WSD

FORMULATION: «drench» for oral administration.

ACTIVE INGREDIENT(S): closantel: 37.5 g/L (=3.75%)

CHEMICAL CLASS of the active ingredient(s): salicylanilide


PARASITES CONTROLLED (spectrum of activity)

  • Liver fluke infections (chronic and sub-acute fasciolosis) caused by Fasciola hepatica (limited efficacy against immature stages)
  • Nasal bots (Oestrus ovis)
  • Haemonchus contortus (Barber Pole Worm) adults, immatures & inhibited larvae


Sheep: 1 mL product/5 kg bw, equivalent to 7.5 mg closantel/kg bw.

  • ≤15 kg: 3 mL product
  • 16-25 kg: 5 mL product
  • 26-35 kg: 7 mL product
  • 36-40 kg: 8 mL product
  • 41-45 kg: 9 mL product
  • 46-50 kg: 10 mL product
  • 51-55 kg: 11 mL product
  • 56-60 kg: 12 mLproduct
  • 61-65 kg: 13 mL product
  • 66-70 kg: 14 mL product
  • 71-75 kg: 15 mL product


  • LD50 (acute oral) in rats: for closantel a.i. 262 to 342 mg/kg (depending on the studies)
  • LD50 (acute dermal) in rats: n.a.

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

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

  • Meat: Australia: 28 days (ESI: 60 days)
  • Milk for human consumption: Australia: DO NOT GIVE during pregnancy or lactation to animals which are producing or may produce 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: YES. Cases of resistance to closantel have been reported for Haemonchus contortus and can be common in ssome regions in Australia. Resistance of Fasciola hepatica, to closantel has been reported as well, but seems not to be widespread in most countries.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it cannot be excluded that this 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 liver flukes through product rotation:

  • Clorsulon: effective only against ≥8 weeks old liver flukes.
  • Nitroxinil: effective only against ≥8 (sheep) or ≥7 (cattle) weeks old liver flukes.
  • Oxyclozanide (salicylanilide): effective only against ≥12 (sheep) or ≥10 (cattle) weeks old liver flukes.
  • Rafoxanide (salicylanilide): effective only against ≥6 weeks old liver flukes.
  • Triclabendazole (benzimidazole): effective against adult liver flukes and all immature stages. However, resistance has been reported in various countries worldwide and is increasing.

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

There are also a few reports on liver fluke populations in sheep resistant to rafoxanide and closantel (both salicylanilides), probably with cross-resistance to nitroxinil, and also to clorsulon. So far resistance to these compounds seems to be less frequent than to resistance to benzimidazoles.

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: Australia.
GENERIC BRANDS available? Yes, but rather few in many countries, if at all. This product itself contains generic closantel.

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

For an overview on the most used antiparasitic drench brands click here.


WSD Closantel is brand with generic closantel marketed in Australia by WSD.

Closantel is a narrow spectrum but rather particular anthelmintic, because it is effective against some internal parasites (e.g. Haemonchus contortus and Fasciola hepatica) and a few external parasites as well (e.g. nasal bots). It has also an effect on the viability of some tick species, but this is usually of no practical use under most field conditions in open systems: numerous alternative hosts allow survival of enough ticks that ensure the infestation of the environment.

Closantel offers good control of adult liver flukes, but efficacy against immatures is incomplete (>5 weeks ~90%; 3-4 weeks <73%): this is important because immature stages are the most damaging ones.

Efficacy against roundworms is usually limited to some blood-feeding species. This is related to the fact that ingested closantel is quickly absorbed to blood where it binds strongly to plasma proteins. There it remains for several days before being excreted. In contrast, its concentration in the tissues is usually too low to kill worms that do not feed blood, which are the majority among the roundworms that infect sheep.

In ruminants, fasting slows the passage of food through the stomach and the gut, which increases the time for absorption of closantel into blood and hence its plasma concentration and bioavailability. Consequently it is recommended to keep healthy animals off food for up to 24 hours before treatment with closantel. This should not be done with heavy pregnant, stressed, or weak animals. Fasting animals should have access to drinking water.

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.