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Revised: November 30, 2023
Published: July 01, 2019

Available as a topical dewormer or as a long-acting injection (six or 12 months)

Brand Name: Advantage Multi, Proheart 6, ProHeart 12, Simparica Trio and many others


Moxidectin is an anti-parasite medication of the macrocytic lactone class. It affects the nervous system of insects and most parasitic worms while leaving the mammal nervous system unharmed. 

How this Medication is Used

Moxidectin is available as a once-a-month topical for the prevention and control of hookworms, roundworms, and whipworms, as well as for the prevention of heartworm infection. The topical product is dosed according to weight range and is applied high enough on the back of the neck to prevent oral exposure. Topical moxidectin may be used in heartworm-infected dogs.

Injectable moxidectin is given once every 6 or 12 months by veterinary staff and is labeled to prevent heartworm infection and to treat and control hookworms. It can be used either all year round or during the heartworm season. If it is to be used seasonally, it should be started within one month of the first mosquito exposure. Injectable moxidectin is not approved for use in heartworm-infected dogs. 

Moxidectin is also effective against ear mites, notoedric mange in cats, and sarcoptic mange in dogs

If a dose of the topical product is skipped, it is important to use it as soon as this is discovered to avoid loss of heartworm protection. If the injectable product is not repeated at the end of the labeled interval, there will be very little residual protection until it is given again.

Side Effects

Side effects with the topical product are unusual if it is used according to instructions but the most common ones include: lethargy, vomiting, diarrhea, weakness, increased thirst, and itching. Hair loss may occur at the application site.

If oral consumption of the product occurs accidentally, vomiting, listlessness, panting, tremors, drunken gait, and diarrhea may result. Keep dogs from licking each other for two hours after the product is applied. 

Cats are sometimes reactive to the topical product, expressing itching, spinning, hiding, rubbing, and excessive grooming. Occasionally, a drunken gait or trembling has been reported. 

If you think your pet is having a side effect of any kind to this medication, notify your veterinarian or call Animal Poison Control at 888-426-4435. 

Interactions with Other Drugs

Drug interactions do not seem to be a concern except in individuals with the MDR-1 mutation, a mutation that influences the transport of certain drugs. Moxidectin is well tolerated by dogs with this mutation; however, if moxidectin is given with another drug on this list, there could be a problem in a dog with the MDR-1 mutation.

How do you know if your dog has the MDR-1 mutation?

This mutation is most common in collie-type breeds but also in Old English Sheepdogs, Australian shepherds, and other white-footed herding breeds. A DNA test kit can be obtained from Washington State University, and your dog can be tested with a cheek swab. 

Concerns and Cautions 

Children should not be allowed to touch the area where topical moxidectin was applied for 2 hours afterward in dogs and 30 minutes in cats.

Tapeworms are not affected by moxidectin as their biology is vastly different from other parasitic worms. 

A dog must be at least 6 months of age to receive the injectable moxidectin product. It should not be used in sick or otherwise debilitated dogs.

Injectable moxidectin should not be given with vaccinations. Anaphylactic reactions, which are life-threatening, have been reported with this practice.

Do not apply the topical product to irritated skin. 

Topical moxidectin products should be stored at room temperature.  

If a dose is accidentally skipped, give the dose when it is remembered. Do not double up on the next dose.

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