Brand: ZANIL Fluke Drench 34 mg/ml Oral Suspension


FORMULATION: «drench» for oral administration.

ACTIVE INGREDIENT(S): oxyclozanide: 34 g/L (=3.4%)

CHEMICAL CLASS of the active ingredient(s): salicylanilide


PARASITES CONTROLLED (spectrum of activity)


CATTLE: 3 ml product/10 kg bw, equivalent to 10 mg oxyclozanide/kg bw.

  • 50 kg: 15 ml product
  • 100 kg: 30 ml product
  • 150 kg: 45 ml product
  • 200 kg: 60 ml product
  • 250 kg: 75 ml product
  • 300 kg: 90 ml product
  • ≥350 kg: 105 ml product

SHEEP: 4.5 ml product/10 kg bw, equivalent to 15 mg oxyclozanide/kg bw.

  • 10 kg: 4.5 ml product
  • 20 kg: 9.0 ml product
  • 30 kg: 13.5 ml product
  • 40 kg: 18 ml product
  • ≥45 kg: 20 ml product


  • LD50 (acute oral) in rats for oxyclozanide a.i.: 980 to 3519 mg/kg (different studies)
  • LD50 (acute dermal) in rats: n.a.

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

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

  • Meat: Cattle & Sheep: 28 days
  • Milk for human consumption: 
    • Cattle>: 72 hours
    • Sheep: Do not use in sheep 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: LOW. So far no cases of liver fluke resistance to oxyclozanide have been reported. 

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it is most likely due to incorrect use and not to resistance. However, prolonged use of the same active ingredient for years bears the risk of resistance development. Therefore periodically changing the chemical class of the active ingredient (product rotation) is highly recommended.

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

  • Closantel: effective only against ≥8 weeks old liver flukes.
  • Clorsulon: effective only against ≥8 weeks old liver flukes.
  • Nitroxinil: effective only against ≥8 (sheep) or ≥7 (cattle) 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: UK and EU countries.
GENERIC BRANDS available? Yes, but rather few in many countries, if at all.

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

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


ZANIL is the original oxyclozanide brand developed by ICI in the 1960s, now owned by MERCK (MSD) ANIMAL HEALTH.

Oxyclozanide is a narrow spectrum flukicide effective against adult liver flukes, without any effect on roundwormstapeworms or any external parasites. It kills only the adult flukes in the bile ducts, but not those immature stages migrating through the liver that are responsible for acute fasciolosis, which are the most harmful ones, particularly for sheep.

Oxyclozanide products have been withdrawn in many countries because more effective flukicides are available, particularly triclabendazole. However, resistance of Fasciola hepatica to triclabendazole (and also to albendazole) has been now reported in numerous countries and is increasing. Oxyclozanide products may be a suitable alternative for liver fluke 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.