Ivermectin for Dogs: A Medication That Can Prevent Heartworms and Other Parasites
Key takeaways:
Ivermectin (Heartgard, Stromectol) is a common preventative parasite medication for dogs. It can prevent heartworms, roundworms, and hookworms.
Ivermectin is safe for most dogs. But it should only be given as directed by a veterinarian.
Dogs most commonly take ivermectin on a monthly basis as part of a parasite prevention plan. It’s available as oral tablets or an injection given by your veterinarian.
Table of contents
All dogs need parasite prevention to protect against heartworms and intestinal worms. Ivermectin (Heartgard, Stromectol) has long been considered a safe and effective parasite preventative for dogs. So it is a common ingredient in monthly parasite preventatives. Ivermectin is also used to treat parasitic infections, like mange, in dogs.
Ivermectin for dogs at a glance
Common names | Ivermectin (Heartgard, Stromectol) |
Uses | Parasite prevention and treatment, including heartworm prevention |
How it comes (forms) | Oral tablets, injection |
Common side effects | Rare at typical dosages |
Cost |
What is ivermectin for dogs, and how does it work?
Ivermectin is an antiparasitic commonly used to treat dogs. When given monthly, it can prevent heartworm infections and intestinal worm infections. Veterinarians may also prescribe ivermectin to eliminate other parasites.
When ivermectin enters a dog’s body, it travels through the bloodstream. Any parasites living in the dog are exposed to the ivermectin through the bloodstream. The medication then paralyzes susceptible parasites, causing them to die.
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What is ivermectin used for in dogs?
Ivermectin is included in many oral, monthly heartworm preventatives. Ivermectin prevents:
Heartworms: Heatworms spread through mosquito bites. When a dog is bitten by an infected mosquito, heartworm larvae can grow into spaghetti-like worms that block the flow of blood in the dog’s heart and lungs. Signs of a heartworm infection include coughing, weakness, and sudden death.
Hookworms: These are common intestinal worms in dogs. Hookworms spread through contact with the feces (poop) of an infected dog or contaminated soil. Hookworms latch onto a dog’ intestinal wall and suck their blood. Signs of a hookworm infection include vomiting, diarrhea, and anemia.
Roundworms: Roundworms are another common intestinal parasite that is spread through contaminated dog poop and soil. Roundworms live within the intestine, stealing nutrition from the host dog. Signs of a roundworm infection include vomiting, diarrhea, and coughing.
Using an ivermectin-based heartworm preventative can ward off these infections. Some heartworm preventatives contain ivermectin along with another parasite prevention medication. This combination provides protection against a broader range of parasites.
Veterinarians also prescribe oral or injectable ivermectin to treat the following parasitic diseases:
Demodectic mange
Scabies
Nasal mites
“Walking dandruff” (cheyletiellosis)
These are off-label uses of ivermectin. In these cases, ivermectin is given at higher doses than those recommended for heartworm prevention. It may also be given more often than once a month.
Got worms? Learn how to identify worms that may show up in your dog’s poop and what you can do about it.
Heartworm prevention: Most dogs should take a preventive heartworm medication to protect against these dangerous pests. Here’s what you need to know.
Prevent fleas and ticks: It’s important to protect your dog against fleas and ticks and the many diseases they cause. Read about your dog’s preventive options.
What is the typical dosage of ivermectin for dogs, and how is it given?
When ivermectin is given on a monthly basis for parasite prevention, the dose is based on a dog’s body weight. Your veterinarian will prescribe the correct dose for your dog. Ivermectin-containing heartworm preventatives often come as chewable, flavored tablets. Give your dog 1 tablet by mouth once monthly, on the same day of the month — or as otherwise directed by your veterinarian.
Off-label use of ivermectin requires a personalized treatment plan. Your dog may need ivermectin as often as once daily or as little as once monthly depending on their diagnosis. Oral and injectable forms of ivermectin are used to treat other parasitic diseases.
What should you do if your dog misses a dose of ivermectin?
If you forget to give your dog a dose of ivermectin, give them the missed dose as soon as you remember. After that, continue giving them ivermectin as recommended by your veterinarian. Do not give your dog a double dose of ivermectin.
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If you forget to give your dog several doses of ivermectin, contact your veterinarian for guidance.
What are the common side effects of ivermectin in dogs?
Heartworm preventatives contain a very small amount of ivermectin. Side effects associated with these medications are very rare.
Neurological side effects may occur with high doses of ivermectin, though. These side effects are more common in dogs with the MDR1 mutation. Dogs with this genetic mutation are more sensitive to many medications, including ivermectin. This mutation is most common in herding breeds, such as collies and Australian shepherds. The MDR1 mutation is diagnosed with genetic testing.
What are the most serious risks of ivermectin for dogs?
Dogs receiving high doses of ivermectin may develop neurological side effects. These may include:
Dilated pupils
Incoordination
Stumbling or “drunken gait”
These serious side effects are extremely rare in dogs receiving an ivermectin-based heartworm preventative. They are only a concern in dogs receiving high doses of ivermectin. This is especially true for dogs that have the MDR1 mutation.
Serious side effects can also occur in dogs who receive too high of a dose of ivermectin. This often occurs when an owner gives their dog an ivermectin medication intended for horses or cattle. Never give large-animal formulations of ivermectin to your dog.
If your dog develops neurologic side effects while taking ivermectin, stop giving them the medication and contact your veterinarian immediately.
Does ivermectin interact with any other dog medications?
Interactions between ivermectin and other dog medications are rare. But dogs receiving high doses of ivermectin or who have the MDR1 mutation are more likely to experience interactions. Your veterinarian will let you know if your dog is at a higher risk for experiencing an interaction.
Tell your veterinarian about any other medications your dog takes. This includes prescription medications, over-the-counter medications, and vitamins or supplements. Doing so can reduce the risk of potentially harmful interactions.
Frequently asked questions
Ivermectin typically starts to kill parasites within 1 to 2 days after a dog takes the oral form. If your dog is given injectable ivermectin at the hospital, it will start working within 1 to 2 hours.
Dogs who take too much ivermectin can be at risk of serious neurological side effects such as:
Dogs are more likely to experience these serious side effects if they’re given ivermectin intended for a much larger animal, like a horse. Never give your dog a medication that has not been specifically prescribed for them.
The bottom line
Ivermectin is a safe and effective medication that prevents a variety of parasitic infections in dogs, including heartworm infections. When used as a monthly parasite preventative, the risk of side effects is very low. Side effects and medication interactions are more common with high doses of ivermectin. This is especially true for dogs with the MDR1 mutation. Be sure to closely follow your veterinarian’s instructions for giving your dog ivermectin.
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References
American Heartworm Society. (n.d.). Heartworm basics.
Brooks, W. (2021). Ivermectin (Ivomec, Heartgard 30, Acarexx, Iverheart Plus). Veterinary Partner.
Brooks, W. (2023). Hookworms in cats and dogs. Veterinary Partner.
Dockweiler, J., et al. (n.d.). Drug sensitivity: MDR1. Cornell Richard P. Riney Canine Health Center.
DVMetrics & Services. (2020). Client drug information sheets: Ivermectin - full version.
Garcia, J. L (2014). Just ask the expert: The best way to treat ivermectin toxicosis. DVM360.
Pets and Parasites. (n.d.). Roundworms. Companion Animal Parasite Council.
Washington State University College of Veterinary Medicine. (n.d.). PrIMe® MDR1 testing for dogs and cats.
