Comparing Heartworm Medicine for Dogs

We recently wrote an article to help educate pet parents on the ins and outs of heartworms. You can find that article here to learn everything to you need to about heartworm disease. Today, we’re going to do a walkthrough of the different heartworm prevention options out there.

Medication Active Ingredients Protects Against Application Frequency of Use Approx Monthly Cost (30lb Dog)
Advantage Multi Moxidectin, Imadacloprid Heartworm, Fleas, Sarcoptic Mange, Roundworm, Hookwork, Whipworm Topical Monthly $14
Iverhart Plus Pyrantel, Ivermectin Heartworm, Roundworm and Hookworm Chewable Monthly $5.70
Heartgard Plus Ivermectin, Pyrantel Heartworm, Roundworm and Hookworm Chewable Monthly $5.40
Interceptor Milbemycin Oxime Heartworm, Roundworm, Hookworm, and Whipworm Chewable Monthly $5.38
Iverhart Max Ivermectin, Pyrantel Pamoate, Praziquantel Heartworm, Roundworm, Hookworm, and Tapeworm Chewable Monthly $5.87
Revolution Selamectin Heartworm, Fleas, Ear Mites, Sarcoptic Mange, 1 kind of Tick Topical Monthly $14.25
Trifexis Spinosad, Milbemycin Oxime Heartworm, Flea, Hookworm, Roundworm, Whipworm Chewable Monthly $17.40
Sentinel Spectrum Milbemycin Oxime, Lufenuron, Praziquantel Heartworm, Flea eggs, Roundworm, Hookworm, Whipworm, Tapeworm Chewable Monthly $8.82
Tri-Heart Ivermectin, Pyrantel Heartworm, Hookworm, Roundworm Chewable Monthly $5.24
Proheart Moxidectin Heartworm, Hookworm Injectable Every 6 months Varies

Once your dog has heartworm disease, there are a few different ways to treat. Preventatives are used to kill the baby heartworms, but special medications are needed to kill the adults.

  1. Immiticide injections: This is the most recommended method and it kills the adult heartworms. A series of injections are given about a month apart to kill the heartworms. This results in the fastest kill rate of the adult heartworms; while these adult heartworms die, dogs must be kept exercise restricted for about a month after each injection to prevent severe, sometimes fatal complications. Other medications, like steroids or antibiotics, may also be used.
  2. “Slow Kill” using heartworm prevention only: NOT recommended except for very sick or very old dogs and can promote heartworm resistance to preventative medications. This method uses certain heartworm preventative medications and can take up 2 years to kill the heartworms. The dog must be kept exercise restricted during the entire treatment period- sometimes years(!)- to prevent serious, sometimes fatal complications.
  3. Surgical removal: For dogs with extremely high numbers of adult heartworms, surgical removal may be recommended.

Does my dog need a heartworm test before starting heartworm preventive medications?

It depends. Usually, very young dogs (less than 4 months) can start without a test. This is at the discretion of your vet, as some regions are at higher risk than others. We also recommend a test for adult dogs annually, or if doses of the preventive medications have been missed. If your dog is an adult and has never had heartworm prevention, we test to ensure that they aren’t already infected. Certain heartworm preventatives can cause health problems if given to an already heartworm-positive dog.

What is the best heartworm prevention for dogs?

When it comes to heartworm prevention, the best prevention is the one that’s right for your dog and its specific needs. It’s important to talk with your veterinarian about your pet’s health to help determine the right heartworm preventive for your dog. These preventatives work by killing baby heartworms before they become adults. Some preventatives also cover intestinal parasites, fleas, ticks, mites, or other parasites too.

What are the possible side effects of giving my dog heartworm preventive?

As with any medication, there is always a risk of side effects. The most common side effects are vomiting or diarrhea, and usually only last for 24 hours following the first one or two doses. Giving heartworm preventative to a dog that has heartworm disease can cause fatal side effects, including pulmonary embolisms and anaphylactic shock due to the uncontrolled death of adult heartworms. Always ask your vet before giving preventatives if you’ve missed a dose!

Our take on heartworm medications

Our veterinarians here at Fuzzy took some time to break down their favorite heartworm medications. These opinions are only for the San Francisco Bay area- different products work better or worse in different parts of the country. 

For effectiveness against Heartworm:

All the products we have listed should be equally effective to prevent heartworm disease in the SF Bay area. Remember that they are only effective if used properly, though!

  • We prefer oral medications over topicals for most pets. Topical medications may not be effective if your pet is washed before or after application, or if applied to the fur rather than to the skin. In addition, they can leave a residue that can be licked by other pets or touched by your children before being fully absorbed. These products are often the easiest to use for cats or dogs that are difficult to give oral medications.
  • You’ll notice a price difference amongst the heartworm preventions, and that’s largely due to how many parasites they prevent. The products that prevent only heartworm can be paired with other preventatives for fleas and/or ticks.

For ease of use:

This depends on your own pet.

  • For topicals: We prefer Revolution over Advantage, as it’s a smaller amount of liquid and is alcohol based. Alcohol based products dry within an hour, while the oil based products like Advantage can leave a greasy spot for up to 48 hours. Ensure that the medication is being applied directly to the skin along the back of the neck (where they can’t turn around and lick it off). We’d also recommend not bathing your pet for 48 hours before and after applications. Dogs that swim a lot may not have full effectiveness, especially with the oil-based topicals.
  • For orals: This is your own pup’s preference. Most food-motivated dogs will eat any of them. Ensure your pet isn’t spitting the medication out when you aren’t watching!
  • For injectables: Easy to use because you don’t have to think about it for 6 months out of the year, but does involve a vet visit and injection every 6 months.

For covering fleas too:

  • Here in the SF Bay area, topicals that are usually over-the-counter, like Advantage or Frontline, do not work well for fleas. This is a very regional problem that depends on your flea population.
  • Sentinel is a great product for heartworm and intestinal parasites, but it’s flea prevention component is not enough to keep the Bay Area’s fleas under control. It only sterilizes the flea eggs, rather than killing the adult flea. Don’t depend on this product for flea control.
  • Trifexis is a great combination product for both fleas and heartworm. When giving this product, open the packaging and let it “air out” for about 30 minutes- some dogs don’t like the smell at first but will readily eat it after the scent has dissipated.

For covering intestinal parasites:

Thankfully, the Bay Area has a relatively low intestinal parasite problem. Other parts of the country (especially the midwest and southeast) have huge loads of intestinal parasites.

  • Check out the Companion Animal Parasite Council’s parasite prevalence maps. This will tell you what intestinal parasites are a problem in your region, so you know which preventative may work the best for you.
  • For dogs that eat other animal’s feces, we’d recommend broad-spectrum coverage.
  • Sentinel Spectrum and Iverheart Max include coverage for tapeworms, a huge problem in the Bay Area due to our monster flea problem. (Eating fleas can give your dog tapeworms!)
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