Company: EQUI AID

DELIVERY FORM: «medicated feed» for daily feeding.

ACTIVE INGREDIENT(S): pyrantel tartrate 9.6 g/lb (20.11 g/kg) (equivalent to 2.11%)

CHEMICAL CLASS of the active ingredient(s): tetrahydropyrimidine


PARASITES CONTROLLED (spectrum of activity)

  • For the prevention of Strongylus vulgaris larval infestation in horses
  • For the control of the following parasites in horses:
    • Large Strongyles (adults): Strongylus vulgaris, Strongylus edentatus
    • Small Strongyles (adults and 4th-stage larvae): Cyathostomum spp., Cylicocyclus spp., Cylicostephanus spp., Cylicodontophorus spp., Poteriostomum spp., Triodontophorus spp.
    • Pinworms (adults and 4th-stage larvae): Oxyuris equi
    • Ascarids (adults and 4th-stage larvae): Parascaris equorum


  • To be administered on a continuous basis either as a top-dress or mixed in the horse’s daily grain ration at the rate of 1.2 mg pyrantel tartrate per lb of body weight daily (equivalent to ~2.65 mg/kg).
  • To achieve this dose, administer 0.5 oz of product per 250 lb of body weight (a CW Continuous Wormer measuring scoop is enclosed).

Read the product label for more specific details on dosage.


  • LD50 (acute oral) in rats: 170 mg/kg for pyrantel tartrate
  • LD50 (acute dermal) in rats: n.a.

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

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

  • Meat: Not for use in horses intended 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

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:

These alternative products may not be available in all countries.

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: USA.
GENERIC BRANDS available? Yes, but not too many in most countries. This product itseg contains generic pyrantel tartrate

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

Click here for an overview on the most used antiparasitic feed additives and medicated feeds for livestock and horses.


CW ® CONTINUOUS WORMER from EQUI AID is a medicated horse wormer with generic pyrantel tartrate.

Pyrantel is a veteran tetrahydropyrimidine introduced in the 1960s (by PFIZER → ZOETIS) that is moderately used in horses, abundantly in pets, but rather scarcely in ruminants. It is a narrow-spectrum anthelmintic effective against roundworms in the gut, but not against those in other organs (e.g. the lungs, the skin, etc). It is also ineffective against gastric bots (Gasterophilus spp) or whatever external parasites.

Pyrantel has no residual effect, i.e. it kills the parasites after administration but as soon as medicated feeding is interrupted it does not significantly protect the animals against re-infestation by infective stages in their environment.


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.