Brand: FARNAM ® WORMA ® PASTE FOR HORSES
Company: INTERNATIONAL ANIMAL HEALTH PRODUCTS
FORMULATION: «oral paste/gel» in pre-charged syringes
- Oxfendazole: 107.2 mg/g (=10.72%);
- Piperazine dihydrochloride: 214.4 mg/g (=21.44%)
CHEMICAL CLASS of the active ingredient(s):
- Oxfendazole: benzimidazole
- Piperazine: Piperazine derivative
PARASITES CONTROLLED* (spectrum of activity)
* Country-specific differences may apply: read the product label.
- Large strongyles (Strongylus spp, Triodontophorus spp)
- Small strongyles including benzimidazole resistant strains (Cyathostomum spp)
- Ascarids (Parascaris equorum) including abamectin, ivermectin and moxidectin resistant strains
- Pinworms (Oxyuris equi)
- Tapeworms (Anoplocephala perfoliata)
*Can be slightly different in some countries: read the product label!
- A 56 g syringe contains sufficient WORMA PASTE to treat a 600 kg horse, equivalent to 10 mg oxfendazole/kg bw and 20 mg/kg piperazine/kg bw.
- The syringe is calibrated in 50 kg divisions.
- LD50 (acute oral) in rats: >5000 mg/kg (estimate calculated according to the WHO based on the ivermectin LD50)
- Estimated hazard class according to the WHO: not applicable for veterinary medicines
Suspected poisoning? Read the articles on oxfendazole safety and/or piperazine safety in this site.
Withholding periods (=withdrawal times) for meat & milk (country-specific differences may apply: read the product label)
- MEAT & OFFAL: AUS: DO NOT ADMINISTER LATER THAN 28 DAYS BEFORE SLAUGHTER FOR HUMAN CONSUMPTION.
- MILK: Do not 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:
- Safety for humans
- Safety for domestic animals
- Safety for the environment
- Hazard classifications of pesticides
Risk of resistance? YES
- Small strongyles (cyathostomes). Resistance of small strongyles to benzimidazoles is widespread and frequent e.g. in Australia, USA, UK and Europe, Argentina, Chile, Uruguay, etc.
- Parascaris equorum: Cases of resistance to benzimidazoles have been reported (e.g. in Australia and the USA). For the time being there are no reports on resistance of this ascarid worm to piperazine.
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:
- Imidazothiazoles, mainly levamisole. Not approved for use in horses in many countries.These alternative products may not be available in all countries, or may not be available as oral pastes or gels.
- Macrocyclic lactones: mainly ivermectin, moxidectin. But tolerance or resistance to these compounds have also been reported in Europe (e.g. in the UK, Germany, Italy), the USA, and Brazil.
- Tetrahydropyrimidines, mainly pyrantel (limited spectrum of activity), but resistance cases have also been reported (e.g. Australia, USA, Brazil, Japan)
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: Australia
GENERIC BRANDS available? YES, probably not too many with piperazine.
Click here to learn more about GENERIC vs. ORIGINAL drugs.
FARNAM WORMA oral paste for horses is a horse wormer from INT. ANIMAL HEALTH PRODUCTS combining oxfendazole with piperazine, nowadays a rather unfrequent combination.
Oxfendazole is a veteran benzimidazole introduced in the 1970s (by WELLCOME) that is moderately used in livestock and horses, rather scarcely in pets. It is a broad-spectrum anthelmintic effective against roundworms in the gut, but not against those in the skin. It is also ineffective against gastric bots (Gasterophilus spp) or whatever external parasites. It is not used in agriculture.
Piperazine is one of the oldest generic anthelmintics. The compounds was already used in the 19th century, although its anthelmintic properties were discovered only in the 1950s. It is a narrow-spectrum anthelmintic, effective mainly against ascarids (Parascaris equorum) in the gut. It is very scarcely used in horses, pets or ruminants, more in pigs and poultry. It is also used in human medicines.
Oxfendazole and pyrantel have no residual effect, i.e. they kill the parasites after administration but do not protect against reinfestation.
The logic oc combining two nematicides (i.e. roundworm killers) such as oxfendazole and piperazine is related to resistance management. Since both compounds have different mechanisms of action, it is assumed that resistance development will be prevented or at least delayed because the risk of simultaneous development of worm resistance to two different mechanisms of action is much smaller than to only one. However, this is only true if the concerned worms are still susceptible to both compounds. Otherwise, if the worms are already resistant to one of them, only one will work. It will initially do the job, but the risk of development of multiple resistance to both compounds is considerable. In addition, this combination may delay resistance development by Parascaris equorum but not by small strongyles, becasue piperazine is not effective against these worms at the recommended dose.
For an overview and a list of the most used oral paste & gel brands click here.
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.