Company: VIRBAC

DELIVERY FORM: «drench» for oral administration.


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.

  • Sheep: 1 mL product/5 kg bw (equivalent to 7.5 mg of levamisole/kg and 3.75 mg of praziquantel/kg)
  • ≤10 kg: 2 mL product
  • 10-15 kg: 3 mL product
  • 16-20 kg: 4 mL product
  • 21-25 kg: 5 mL product
  • 26-30 kg: 6 mL product
  • >31 kg: add 1 mL per 5 kg


  • LD50 (acute oral) in rats:
  • LD50 (acute dermal) in rats: n.a.

Suspected poisoning? Read the articles on levamisole safety and on praziquantel safety in this site.

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

  • Meat: UK: 28 days
  • Milk for human consumption: UK: milk from treated sheep must not be used 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, resistance of gastrointestinal roundworms to levamisole in ruminants is a serious and increasing problem, particularly in sheep and goats, but also in cattle. Levamisole resistance is usually less strong and widespread than resistance to benzimidazoles, but nevertheless a serious problem. The most affected worm species in sheep are: Haemonchus spp, Ostertagia spp /Teladorsagia spp, Trichostrongylus spp, Nematodirus spp, Chabertia ovina.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it can 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 drenches, or may not be effective against all the concerned parasites.

It is highly recommended to periodically check the resistance status of each property performing appropriate tests (e.g. fecal egg counts) under supervision of a veterinary doctor. Such tests are now routinely available for most producers in developed countries.

So far there are no significant problems of tapeworm resistance to praziquantel in sheep.

Learn more about resistance and how it develops.


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

  • Levamisole: GENERIC (introduced in the 1960s by JANSSEN)
  • Praziquantel: GENERIC (introduced in the 1970s by BAYER)

*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.
GENERIC BRANDS available? Rather few, if at all, with this particular composition: praziquantel is rarely used on livestock.

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

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


FIRST DRENCH is a local brand from VIRBAC containing generic levamisole and praziquantel.

Levamisole is a veteran anthelmintic. It was introduced by JANSSEN already in the 1960s (NILVERM, RIPERCOL). It has a broad-spectrum of activity against roundworms (gastrointestinal and pulmonary) but no efficacy whatsoever against tapeworms and flukes. It is also completely ineffective against external parasites of livestock (ticksflies, lice, mites, etc). Levamisole has been used massively worldwide in countless generic formulations. It still remains one of the most preferred low-cost anthelmintics for livestock worldwide.

Praziquantel is another veteran anthelmintic introduced in the 1970s by BAYER. It is the most widely used active ingredient against tapeworms in pets, but is rarely used for livestock. Praziquantel has no efficacy whatsoever against roundwormsflukes or any external parasites (ticksflies, lice, mites, etc).

As many other anthelmintics (e.g. benzimidazoles, monepantel, and tetrahydropyrimidineslevamisole and praziquantel administered as a drench have no residual effect, i.e. they kill the parasites shortly after administration, but do not significantly protect the animals against re-infestation by infective stages in their environment.

Thanks to its higher solubility in water levamisole is also available as a pour-on and as an injectable for livestock, but only in some countries.

Unfortunately, resistance of several gastrointestinal roundworms to levamisole is already very high and very frequent worldwide in sheep and goats, slightly lower in cattle, which has significantly reduced its usage in livestock. Nowadays more convenient pour-ons and injectables containing macrocyclic lactones (e.g. abamectin, doramectin, eprinomectin, ivermectin, moxidectin) are often preferred over drenches with levamisole or benzimidazoles. Macrocyclic lactones (ML) also ensure several weeks protection against re-infestation by several worm species, in contrast with levamisole or benzimidazole drenches that lack any residual effect. However, resistance of gastrontestinal worms to ML is alredy quite frequent in sheep and goats, less common in cattle but increaising.

In ruminants, reducing the amount of feed slows down the exit flow of the rumen and prolongs the time during which the active ingredient remains there and is absorbed. Consequently it is advisable to reduce the access of animals to feed (especially to fresh pasture, not to water) 24 hours before administration. For the same reason, it is better to keep the animals away from food for about 6 hours after drenching. However sick or weak animals should not be kept away from food and fasting animals should have access to 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.