Make sure you know the facts about Moxidectin®


Commonly Asked Questions About Moxidectin

Below are several common questions about moxidectin:

What is moxidectin, and how does it work?

Moxidectin is an active ingredient found in products given to animals, such as dogs, cats, horses, and cattle, for the prevention, treatment and / or control of common internal and external parasites, such as heartworms. Products with moxidectin come in different forms, including orals, topical solutions, and injectables. Talk to your veterinarian about what treatment is best for your pet and how to use it correctly.

Moxidectin works by selectively binding to high affinity glutamate-gated chloride ion channels and agonist activity at GABA complexes, which are critical to the function of invertebrate nerve and muscle cells. This interferes with the parasite's neurotransmission, resulting in its paralysis and ultimately death.

What are side effects seen in products using moxidectin?

Side effects of moxidectin vary by animal, and may be affected by how the product is formulated, how it is applied, and the dosage used.

Studies of moxidectin's side effects in dogs show that some may experience lethargy, inappetence or anorexia, adipsia, emesis, dyspnea and facial edema, hypothermia, and sensitivity and cutaneous lesions at the site of the moxidectin application (nodule, crusts and purulent exudate).1 Overdoses of moxidectin in dogs may result in dysorexia, sialorrhea, mydriasis, and fasciculations and ataxia of the pelvic limbs.1 In avermectin-sensitive dogs, reactions may be more severe and may include coma and death.

Canine treatments containing moxidectin may be administered as a topical, oral or injectable. It's important that you give the exact dose your veterinarian recommends and apply it as it is stated on the label. If you are ever unsure, ask your veterinarian to show you how to apply the treatment.

Moxidectin is also used in products to treat horses for large and small strongyles, encysted cyathostomes, ascarids, pinworms, hair worms, large-mouth stomach worms, and horse stomach bots. Data shows that horses less than six months of age who are treated with those products have a higher incidence of adverse reactions, including ataxia, apparent depression/lethargy, and recumbency.2

Cattle and sheep receiving an injectable solution at three times the therapeutic dose may experience some transitory nervous symptoms.3

What does avermectin sensitivity mean, and what are its symptoms, causes, and prognosis?

Some herding dog breeds (e.g., collies) may have a mutation to their MDR1 gene that can result in higher levels of certain drugs crossing the blood-brain barrier into the pet’s central nervous system. This condition applies, in theory, to avermectins, the treatment most commonly used for the prevention of heartworm disease. If an avermectin sensitive dog were to inappropriately orally receive a high level of an avermectin such as moxidectin, an adverse reaction could result, but when administered as directed, avermectins are safe for avermectin-sensitive dogs even at levels greater than their prescribed dosages.

If your dog is avermectin-sensitive, talk to your veterinarian about your heartworm disease preventative options. To find a list of drugs and learn about an avermectin sensitivity test now available, go to

What products currently have moxidectin in them?

  • Advocate® for Dogs (Not for sale in the U.S.)
  • Advocate® for Cats (Not for sale in the U.S.)
  • ProHeart®6, manufactured by Fort Dodge Animal Health (for sale in Canada and Japan)
  • ProHeart®12, manufactured by Fort Dodge Animal Health (for sale in Australia)
  • CYDECTIN® for cattle and sheep, manufactured by Fort Dodge Animal Health
  • QUEST® Gel, for horses, manufactured by Fort Dodge Animal Health
  • Advantage Multi™ for Dogs, (imidacloprid + moxidectin) Topical Solution, manufactured by Bayer Animal Health
  • Advantage Multi™ for Cats, (imidacloprid + moxidectin) Topical Solution, manufactured by Bayer Animal Health

How do I report an adverse reaction in my pet?

Report any problems with veterinary drugs and devices for animals to your veterinarian, the drug manufacturer and the Food and Drug Administration's Center for Veterinary Medicine at 1-888-FDA-VETS (1-888-332-8387). Go to for the FDA's reporting form.

How does the FDA evaluate products with moxidectin?

Depending upon the specific ingredients, products used to prevent, treat and/or control external and/or internal parasites must be approved either by the Food and Drug Administration (FDA), or the Environmental Protection Agency (EPA). Manufacturers of these products must submit extensive preclinical and clinical data supporting the safety and efficacy of these treatments. The federal regulatory agencies extensively evaluate the data, weighing the benefits vs. risks, before approving a treatment. Regulatory agency monitoring does not end at approval; they continue to monitor the safety of the treatment for the entire time it is on the market.

Since ProHeart 6 was voluntarily withdrawn from the market, why does the FDA allow other drugs with moxidectin to remain?

Working with the FDA, a decision was made by Fort Dodge to voluntarily withdraw ProHeart 6 from the market. Subsequent evaluation of a link between the product and reports of adverse events by both the FDA and the manufacturer proved inconclusive. ProHeart 6 remains on the market in Canada and Japan, and as ProHeart 12 in Australia.

It is important to recognize that even though moxidectin is an active ingredient in ProHeart 6, the other products currently on the market with moxidectin are completely different based on their formulations and routes of administration. Prior to being sold in the United States, any animal health product, including those with moxidectin, must go through a rigorous review by regulatory agencies and continue to be evaluated for safety even after they are approved.


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Commonly Asked Questions