Preventing heartworm disease in dogs makes more sense than waiting for your dog to get the full-blown disease and spend thousands of dollars on expensive treatments that can never really guarantee 100% cure. Not only are you protecting your beloved pet from this potentially deadly disease brought by mosquitoes, you are also ensuring their highest level of quality of life. In this article we’ll take a look at the 5 best heartworm medicines for dogs to help you provide better protection for your pet against this potentially deadly, albeit highly preventable disease.

dog heartworm medicines

1. HeartGard Plus

Considered as the best when it comes to preventing heartworm disease in dogs, HeartGard Plus contains the proven combination of Ivermectin and Pyrantel that is fully capable of not only killing and eradicating Dirofilaria immitis microfilariae from your dog’s circulation but also of treating and controlling 2 roundworm species and 3 hookworm species. It should be noted that Ivermectin is also well-regarded when it comes to the management of demodectic mange and dog lice.

Made by the same company that brings to the pet world the Frontline flea medication, HeartGard Plus is an easy-to-administer formulation that is available in real beef flavor. This helps simplify the process of administration and ensure better protection for your dog against heartworms, roundworms, and hookworms. It is the most prescribed heartworm preventative in the veterinary world, giving you a sense of security regarding its clinical effectiveness and safety profile.

heartgard plus

Key Features

  • Contains Ivermectin and Pyrantel
  • Triple action: kills heartworm larvae, hookworms, and roundworms
  • Once-monthly chewable tablet administration
  • Real beef-flavor chewable tablet formulation

Related Post: Best Flea Collar for Dogs

2. Advantage Multi

From the makers of Advantage and Advantage II flea treatment, a popular flea collar, and Drontal dewormer come Advantage Multi, a preparation that is especially designed to protect your dog against the dreaded Dirofilaria immitis worm. Instead of using Ivermectin as its principal heartworm preventative, Advantage Multi uses Moxidectin instead. This choice of active ingredient gives the Advantage Multi true advantage over other preparations in that it is fully capable of controlling heartworms, whipworms, hookworms, roundworms, and even sarcoptic mange that can bring a very intense itch and reddish crusting patches of skin on dogs.

The inclusion of Imidacloprid takes care of another nuisance to the canine world – fleas. This gives Advantage Multi the capability to control and manage 6 different organisms that commonly plague man’s best friend. It is available as a waterproof spot-on topical application that should be applied every month. While it is waterproof one should wait 60 and 90 minutes after swimming and bathing, respectively to ensure optimum clinical effectiveness.

advantage multi

Key Features

  • Contains Imidacloprid and Moxidectin
  • Kills heartworm microfilariae
  • Controls and removes roundworms, whipworms, sarcoptic mange, and hookworms
  • Kills adult fleas
  • Once monthly topical spot-on waterproof application

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3. Interceptor Plus

Milbemycin oxime, the principal active ingredient of Interceptor Plus, is a known antiparasitic agent that has a very broad spectrum of activity against helminths and mites. It is for this very reason that Interceptor Plus is considered as one of the best in the prevention of heartworm disease in dogs. Since it is also anthelminthic, it can also act against hookworms, whipworms, and roundworms so you can ensure your dog will not have to suffer from these intestinal parasites. The addition of Praziquantel in its formulation gives the Interceptor Plus an exceptional anti-tapeworm activity, especially against Diplidium caninum, Taenia pisiformis, Echinococcus granulosus, and Echinococcus multiocularis species. Interceptor Plus comes in a chewable tablet formulation with real chicken flavor to help ensure easier once-monthly administration. It may not be as popular as HeartGard Plus, but the Interceptor provides the added benefit of controlling tapeworm and whipworm infections in dogs, aside from being a heartworm preventative, of course.

interceptor plus

Key Features

  • Contains Milbemycin oxime and Praziquantel
  • Kills Dirofilaria larvae
  • Controls tapeworms, whipworms, roundworms, and hookworms
  • Once-monthly oral administration
  • Real chicken-flavor chewable tablet formulation

4. ProHeart 6

Some pet parents are not really good of keeping track of their dog’s monthly heartworm preventatives. Some may also have some issues feeding chewable tablets to their pets. Some also have difficulty applying spot-on topical applications on the backs of their dog. If you’re like any one of these the ProHeart 6 is for you.

From the same company that brought you Rimadyl analgesic, Selamectin anthelminthic, and Draxxin antibiotic, ProHeart 6 is a special formulation of Moxidectin that kills Dirofilaria immitis larvae for an astonishing 6 months, requiring only twice yearly administration. It is also formulated as an injectable, effectively bypassing the acidic environment of the stomach and small intestines. It works a lot faster than topical spot-on applications since it is administered into your dog’s subcutaneous tissue which is a lot closer to the blood vessels supplying the skin. It may cost more on a per treatment basis, but if you factor its twice-yearly dosing plus clinical effectiveness, ProHeart 6 still comes out as a great heartworm preventative. And since Moxidectin has a very broad spectrum of anthelminthic activity, it can also help control hookworm, roundworm, whipworm, and sarcoptic mange infections.proheart 6 for dogsKey Features

  • Contains Moxidectin
  • Injectable heartworm preventative offering 6 months protection
  • Convenient twice-yearly dosing instead of 12 monthly doses
  • Kills circulating heartworm microfilariae for 6 months

5. Tri-Heart Plus

The Tri-Heart Plus is a more practical alternative to the leading HeartGard Plus heartworm medication for dogs. It is manufactured by the same company that brought us Bravecto flea treatment and Panacur anthelminthic. Tri-Heart Plus contains the same ingredients found in HeartGard Plus, Ivermectin and Pyrantel, providing the same therapeutic effectiveness and dosing scheme. While HeartGard Plus comes in real beef flavor, studies have confirmed that dogs given the two preparations cannot really differentiate the taste, making the administration of Tri-Heart Plus as easy as administering the once-monthly dose of HeartGard Plus.

That being said, the main advantage of Tri-Heart Plus will be its price which currently stands to be at least 20 percent lower than HeartGard Plus. If any you will just have to choose which between Boehringer Ingelheim (makers of HeartGard Plus) and Merck Veterinary Health (makers of Tri-Heart Plus) you believe has a more stellar performance when it comes to veterinary healthcare products. It’s worth noting that both are recognized brands in human and animal health industries.

tri-heart plus

Key Features

  • Contains Ivermectin and Pyrantel
  • Triple action: kills heartworm larvae, roundworms, and hookworms
  • Once-monthly chewable tablet administration
  • 20% lower price than leading brand

Best Heartworm Medicines for Dogs Buying Guide

Aside from the products that we have featured herein, there are other notable heartworm medicines for dogs in the market. Some are recognized brands while others are generic formulations. To help you decide on which of these products you will eventually buy, we implore you to read our buying guide.

Does My Dog Need a Heartworm Test Before Starting Heartworm Preventive Medications?

The current recommendation is to test all dogs for heartworm infection before the initiation of heartworm preventative therapy. The reason is quite simple. Heartworm preventatives are only effective against microfilariae, the larvae of Dirofilaria immitis, but not on adults themselves.

When a dog that has heartworm infection is bitten by a mosquito, the microfilariae present in its blood are ingested by the mosquito. The microfilariae undergo development in the mosquito, reaching full infectivity within a month. When the mosquito bites another dog, it injects the infective microfilariae into the new dog’s bloodstream where they migrate towards the heart and its associated major blood vessels. These microfilariae eventually grow into adults fully capable of reproducing ne microfilariae in as little as 6 months.

Given that there are no clinical manifestations in your dog at this time, owing to the fact that adult heartworms haven’t fully exacted their damage on the heart just yet, it is imperative that blood tests be administered to determine the presence of microfilariae in the blood. If microfilariae is present and a heartworm preventative is initiated there is the danger of causing an anaphylactic shock in dogs that are more susceptible to developing a hypersensitivity reaction.

In other words, if you give a heartworm preventative to a dog that has a full-blown heartworm disease, this will not kill the adult heartworms. And although it will kill the microfilariae, it will not remove them from the blood. In hypersensitive dogs, the immune system may attack the dead microfilariae in a very disproportionate manner causing anaphylaxis, shock, and even death.

It is for this very reason that testing should always be done first before the initiation of heartworm preventatives. Additionally, annual testing is recommended on all dogs whether or not they are receiving heartworm preventatives.

heartworms in dog

What is the Best Heartworm Prevention?

Looking for the best heartworm prevention can be tricky as each product has its own merits based on their active ingredients. For instance, Ivermectin has always been considered as the gold standard in the prevention of heartworm disease. However, there have been issues related to its side effects. Newer medications such as Moxidectin and Milbemycin oxime offer a much safer profile while also expanding the breadth of their spectrum of activity.

To help you narrow your choices for the best heartworm prevention, you may want to answer the following questions:

  • How much are you willing to spend for a monthly dose of a heartworm preventative?
  • Does your canine friend have allergies and, if so, are you familiar with the specific ingredients that you must avoid?
  • Do you need to protect your pet against heartworm disease only or are you also entertaining protection against other parasites such as fleas, ticks, intestinal worms, mites, and lice?
  • Which manner of heartworm medication administration are you most comfortable with?
  • Can you stick to the regimen on a regular basis?

Your answers to these questions should you determine the best heartworm prevention for you.

What are the Possible Side Effects?

Heartworm medications are guaranteed to be safe. When administered in the correct manner, observing all the precautions as recommended by the manufacturer, these heartworm medicines for dogs are safe for all breeds.

However it is not uncommon that some dogs may show some signs of side effects with the administration of these medications. While these incidents may be infrequent it is still important to remain vigilant during the administration of such preparations. One important thing to understand is that different heartworm medicines for dogs may have different side effects owing to the differences in their active ingredients. The following are the most common side effects caused by the different ingredients used in these canine medications.

  • Dehydration
  • Depression
  • Diarrhea
  • Dilated pupils
  • Disorientation
  • Excessive hypersensitivity to touch or tactile stimulation
  • Excessive salivation or drooling
  • Inability to get up or rise from a lying down position
  • Inability to maintain a steady gait or lack of coordinated movements
  • Lethargy or weakness
  • Loss of appetite
  • Muscle spasms or tremors
  • Temporary blindness
  • Vomiting or retching
  • Weakness or lethargy

Since most heartworm medications don’t come as single ingredient formulations, often combined with an anthelminthic or an antiparasitic agent, the side effects that you can see from your dog may include not only these manifestations that we have listed but also those that are attributed to the antiparasitic agent like Praziquantel, Pyrantel, and Imidacloprid. Suffice it to say these medications should never be administered as an Over-the-Counter medication since the side effects can be exceptionally worrisome. Your veterinarian should always be involved in the management of heartworm disease in dogs.

heatworm sick dog

It is also important to watch out for signs of hypersensitivity or allergic reactions from the active ingredients of these medications. For instance, if your see swelling in your dog’s face, tongue, or even oral cavity, then it is safe to say that your dog may have developed an allergic reaction to one or both of the active ingredients of the medicine. Other manifestations of an allergic reaction can include intense itching, labored breathing, or even sudden onset of diarrhea. In more severe allergic reactions cold limbs, pale gums, and vomiting may precede seizures and shock which can ultimately lead to coma.

If you see any of these reactions don’t waste time. Bring your pet immediately to a vet clinic for appropriate management of the hypersensitivity or allergic reaction.

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3 Common Types of Pet Heartworm Meds

If you are going to look at our list of the 5 best heartworm medications for dogs you will notice that there are 3 fundamental types of these kinds of pet medicines. They are as follows.

  • Oral chewable tablets

These preparations are, by far, the most common and perhaps the easiest to administer to dogs. Many formulations are designed to mimic doggie treats which can help ensure easier administration. Even the flavor is enhanced to increase palatability. In our selection, we have seen products that come in real beef and real chicken flavors, two of the well-loved flavors by members of the canine family.

However, there will always be instances when your dog may need some type of ‘bribing’ to take in the chewable tablet. As such, these formulations may have to be hidden in pill wraps or even wrapped in molded cheese or mixed with their dog food.

These are effective once-monthly preparations, except that their clinical effectiveness may be affected by a number of factors such as the health of the dog’s digestive system as well as the integrity of the blood vessels lining the small intestines where the active ingredients of the medicine are absorbed. If there are any issues in these organs, then it is likely that your dog may not obtain the full preventative benefits of these heartworm medications.

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  • Topical spot-on applications

These preparations are very similar to the once-monthly application of a spot-on flea treatment along the back of your dog. There are some issues about these preparations focusing on the manner of administration, waterproofing, and the accuracy of absorption of the active ingredient or ingredients.

Some pet parents have difficulty applying these medications on their dogs’ back especially if they have a mighty wiggler. While it is easy to restrain your dog just so you can apply the medication, you’re actually bringing unnecessary stress to your pet. There is also difficulty in applying the liquid on dogs with coats that are very difficult to part. Since the medicine needs to be applied onto the skin and not on the hair of your dog, it is crucial that the fur be parted completely to gain access to the skin. If the hair is not parted, some of the medication will be placed on the hair which can be shaken off by your dog once it waggles. This can lead to not administering the recommended dose.

There is also the question of waterproofing with some folks saying one should never wet their dog’s hair and skin at least 3 days before and after the administration of these topical preparations. Thankfully, the product we shared in the list can be fully waterproof within 90 minutes after administration.

Related Post: Best Flea Treatment for Dogs

  • Injectables

One of the greatest advantages of injectable heartworm medicines for dogs is that they start working almost immediately. This is because they are administered into the subcutaneous layer of the skin, shortening the distance needed by the medication to reach the bloodstream. It also bypasses the acid environment of the stomach and the digestive enzyme-rich milieu of the small intestines.

Additionally, as can be noted in one of the products we featured, injectable preparations have a much longer-lasting heartworm preventative effect. If oral and topical medications have to be repeated on a monthly basis, injectables only need to be administered twice a year, giving it a maximum duration of effectiveness of 6 months. This is perfect for pet parents who may have issues keeping up with their dog’s monthly heartworm medication dosage schedule.

Things to Consider Before Buying

Whenever you buy heartworm medicine for your dog, it is important to talk with your veterinarian first. As we have already mentioned, the current recommendation is for heartworm testing to be conducted first before initiating the therapy. But if you insist on buying heartworm medicine without your vet’s guidance, here are some things to consider.

  • Active ingredient

Pay close attention to the active ingredient or ingredients of the product you wish to buy. While all of the active ingredients currently in use in many heartworm medicines today are proven effective, they may differ in the side effects that they produce. What you want is something that is effective yet poses no substantial threat to your pet’s safety.

  • Additional purposes

Are you interested only in preventing heartworms or would you like to protect your pet against other parasites as well? If this is the case you may want a product that has an additional active ingredient or one that has a broad spectrum of activity to help protect your pet against other infections such as intestinal parasitism, flea and tick infestations, and even sarcoptic and demodectic mange.

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  • Age and weight of your dog

Like all medications administered to our dogs it is imperative that you take into consideration your pet’s age and weight. Different products come with different dosage recommendations depending on the age and weight of the dog receiving the medication. It is important to choose the correct dosage that is appropriate for your dog’s age and weight to help avoid under- or over- dosing. Under-dosing your dog will not give it the protection it needs. Over-dosing it may lead to the development of adverse reactions.

  • Formulation

We discussed in the preceding section the different types of heartworm medications. You’ll have to choose one that you are more comfortable administering to your dog. The ease of administration of any canine medicine can be a huge factor when it comes to choosing the right product to use.

  • Cost

Heartworm preventatives are not cheap, especially those that are branded and have very strong presence in the market. While there are cheaper alternatives – generics – there is always this negative image associated with such products with many believing they are not the same with their branded counterparts. So, if you’re presented with two competing well-known brands with exactly the same composition and effectiveness, you may be inclined to choose the brand that is less expensive.

Preventing heartworm disease in dogs is more practical than waiting for the disease to manifest itself. We owe this much to our beloved pets to protect them from this highly preventable harm. Otherwise, how else could we call ourselves as pet parents? With these 5 best heartworm medicines for dogs you’re actually embarking on a personal mission to guarantee the quality of life of your pet.


  1. Heartworm Basics, American Heartworm Society
  2. Heartworm Disease in Dogs, VCA
  3. How is Heartworm Disease Treated in Dogs?, PetMD


Olivia Williams
Olivia is our head of content for, mum of one and a true animal lover. With 12 different types of animal in her family, it's never a dull moment. When she isn't walking the dogs, feeding the cats or playing with her pet Parrot Charlie, you will find her product researching and keeping the site freshly updated with the latest products for your pets!


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