A way to improve or resolve a condition or diagnosis. This might include resolving the underlying cause or treating the signs of disease (symptomatic treatment).

Cost: Under $100

These cost ranges are approximate and may vary from region to region.
Additional charges may also apply.

YOUR VET MAY Recommend

Deworming, Ivermectin

Cost: Under $100

These cost ranges are approximate and may vary from region to region.
Additional charges may also apply.


Ivermectin has been the most important equine anthelmintic (anti-worm) drug since its development in the early 1980's. For equine use, it has been the main representative of a revolutionary drug class called the macrocyclic lactones. Macrocyclic lactones work by blocking the parasite's nerve transmission, causing paralysis and death. The drug is effective against most species of internal parasites and some external parasites. It is especially effective against bots.

Ivermectin is a potent worm killer, even at doses much lower than other classes of dewormer. Both moxidectin and ivermectin also kill external parasites, such as lice, mites, ticks and the skin-dwelling larvae of parasites such as Onchocerca and Habronema.

Ivermectin is relatively safe in horses, and has been shown to be safe in foals, breeding stallions and pregnant and lactating mares.

Ivermectin is mostly used as 1.87% paste formulations but can also be purchased as a 1.87% liquid, which may be more cost-effective for large numbers of horses. Injection of ivermectin is not recommended in horses.

The problem with ivermectin is common to all the anti-parasitic drugs at this time. Inappropriate use is resulting in the emergence of drug resistance in the parasite population. For this reason, it is critical that this drug be used as part of a targeted worming program based on veterinary fecal testing.


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 ivermectin 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.

my vet's role


Related Observations

This treatment might be used for a horse exhibiting these signs.

Very Common
Less Common
more observations


Ivermectin is a relatively safe drug in horses. Very rarely, ivermectin causes neurologic signs in horses. These signs include wobbliness, weakness, depression and even seizures.

In horses with brain disease or injury (loss of the blood-brain barrier), the use of ivermectin could be more dangerous.

Ivermectin can be toxic to Collie breed dogs. Ivermectin paste intended for a horse but inadvertently ingested by a Collie breed dog could be toxic.


Ivermectin should not be administered to horses that have brain disease or injury.

Ivermectin should no longer be used on a rotational basis without fecal testing.

Ivermectin is not effective against tapeworms (Cestodes), Flukes (Trematodes), or encysted small Strongyles.

Ivermectin has poor activity against ascarids. For this reason it is no longer recommended in horses under 1 year of age.

your role

Is it working? Timeframe for effect.
In most cases, you will see nothing after administration of an anthelmintic drug. However, in horses that have large visible worms (ascarids), you may see dead worms in the manure for a day or two after treatment.

In horses for which chronic parasitism is suspected, you can expect to see improvements in weight and haircoat appearance within weeks following treatment.

The only reliable way to determine the effectiveness of a particular deworming compound is to perform a fecal egg count reduction test (FECRT). A fecal egg count is performed on the horse. The dewormer is administered. Two weeks later, a second fecal egg count is performed. If the dewormer is effective, then the egg count of the second sample should be zero. Talk to your vet about creating a proper deworming protocol for your horses.
Questions To Ask Your Vet:
  • Do ivermectin products have any place in my parasite control strategy?
  • How often should you do fecal exams?
  • What management changes should I make to reduce the worm burden in my horses?
  • When should fecal testing be performed to determine the effectiveness of my deworming program?

further reading & resources


Brand Name Products

Equine health related brand name products and services.

  • Bimedia Inc. Equimax® Paste (ivermectin 1.87% praziquantel 14.03%), Deworming
  • Bimedia Inc. Equell® Paste (ivermectin 1.87%), Deworming
  • Bimedia Inc. Bimectine® Paste (ivermectin 1.87%), Deworming
  • Merial Zimecterin® Paste 1.87%, Deworming
  • Merial Eqvalan® Paste 1.87%, Deworming
  • Merial Zimecterin® Gold Paste, Deworming
  • Horse Health Horse Health Equine Ivermectin Paste 1.87%, Deworming
  • Farnam IverCare® Paste (ivermectin 1.87%), Deworming
  • Zoetis Animal Health Equimax, Deworming
  • Med-Pharmex Animal Health Iversol, Deworming
  • AgriLabs Agri-Mectin® Paste 1.87%, Deworming
  • Durvet Animal Health Inc. DuraMectin™ Paste (ivermectin 1.87%), Deworming
  • Med-Pharmex Animal Health Ivermectin Paste 1.87%, Deworming
  • First Companion Iverchoice® Equine Paste 1.87%, Deworming
  • First Companion Ivermax® Equine Paste Dewormer, Deworming
  • Henry Schein® Animal Health Parid EQ™ Liquid for Horses, Deworming
  • Henry Schein® Animal Health Parid EQ Paste™ 1.87%, Deworming
  • RXV Ivermax™ Equine Oral Fluid, Deworming
  • Phoenix Pharm Ivercide™ Equine Paste 1.87%, Deworming
  • VedCo ProMectin E™ Paste, Deworming
  • VedCo Equi-Phar ProTal™ Suspension, Deworming
  • Sparhawk Laboratories Inc. SparMectin-E, Deworming
  • VetOne Vetrimec™ Equine Oral Liquid for Horses, Deworming
  • VetOne Vetrimec™ Paste 1.87%, Deworming
  • Vetoquinol USA Equimax (ivermectin/praziquantel), Deworming
  • Vetoquinol USA Bimectin (ivermectin), Deworming
  • Durvet Animal Health Inc. Ivermectin Paste 1.87%, Deworming

Author: Doug Thal DVM Dipl. ABVP