Horse Side Vet Guide ®

Equine Health Resource

Deworming, Pyrantel Pamoate & Tartrate


Pyrantel pamoate is the compound in most paste and liquid deworming formulations whereas the tartrate salt is the compound contained in continuous dewormers.

Pyrantels mimic the activity of acetylcholine, a natural neurotransmitter that causes muscle contraction. In susceptible worm species, the pyrantels cause irreversible muscle contraction, resulting in rigid paralysis and death. Pyrantel causes a rapid die-off of susceptible worms.

Pyrantel does not penetrate the intestinal wall and so does not kill encysted strongyles.

There is growing small strongyle resistance to this compound. It is quite effective against pinworms. At high doses it has some activity against tapeworms but it is not considered as effective as praziquantel.


The usefulness of any anthelmintic medication depends not only on the effectiveness of the drug against a particular parasite species, but also on the drug’s pharmacology (how much of the chemical is exposed to the parasite in question and for how long), characteristics of the host animal (general health and immunity) and characteristics of the parasite (not only its susceptibility to the anthelmintic but also its location in the body and susceptibility at various life stages to the drug).

Your vet suggests pyrantels as the best choice deworming compound based on results of fecal diagnostic testing and identification of specific parasites affecting your horses.


Horse owners play a vital role in the use of anthelmintic drugs. All anthelmintic drugs should be administered as part of a targeted deworming program along with management techniques to reduce intake of infective parasites.

Random rotational use of dewormers without fecal testing is leading to parasite resistance and the rapid loss of effectiveness of this and other deworming compounds.

Consider Potential Side Effects & Complications

Pyrantel pamoate is safe for equines at up to five times the recommended dose.

Continuous dewormers are widely considered to favor parasite resistance by being at low levels in the horse and the environment at all times.

Anthelminitic medications may have ecologic effects when they are excreted in manure. The full impact of these effects is not yet known.

Consider Reasons Not To Use This Treatment

Because of growing parasite resistance, pyrantel should no longer be used as part of a rotational worming program without veterinary guidance.

Is It working? Timeframe for effect

These products cause a rapid die-off of susceptible parasites. In equines with significant populations of adult worms, expect to see dead parasites in the manure within hours to days.

Questions To Ask My Vet

  • What management changes should I make to reduce the worm burden in my horses?
  • Does this compound really have a place in my deworming program?
Bimedia Inc. Exodus® Paste (pyrantel pamoate), Deworming
Farnam Equi Aid Strongyle Wormer, Deworming
Farnam Equi Aid CW® Continuous Wormer, Deworming
Zoetis Animal Health Strongid® C (pyrantel tartrate), Deworming
Zoetis Animal Health Strongid® C2X™ (pyrantel tartrate), Deworming
Zoetis Animal Health Strongid® Paste (pyrantel pamoate), Deworming
Zoetis Animal Health Strongid® T Suspension (pyrantel pamoate), Deworming
Aspen Veterinary Resources Ltd. Cooper's Best Equistrength™ Paste, Deworming
Durvet Animal Health Inc. Pyrantel Paste (pyrantel pamoate), Deworming
First Companion Equistrength® Paste, Deworming
Henry Schein® Animal Health Pyrantic Paste, Deworming
Equi Aid Strongyle Wormer Equine Anthelmintic, Deworming
Phoenix Pharm Anthelban® V, Deworming
Equi Aid CW® Continuous Wormer Equine Anthelmintic, Deworming
Vetoquinol USA Exodus (pyrantel pamoate), Deworming
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Author: Doug Thal DVM Dipl. ABVP


Bowman DD. Georgis' Parasitology for Veterinarians 9th Ed. Elsevier 2009.


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