Reviewed & Fact-Checked By
Dr. Paola Cuevas
Veterinarian, MVZ
Reviewed & Fact-Checked By
Dr. Paola Cuevas
Veterinarian, MVZ
The information is current and up-to-date in accordance with the latest veterinarian research.
Heartworm disease can be fatal for our beloved dogs, but it’s also very preventable. Regularly administering heartworm medication is highly effective in protecting your dog.
Most heartworm medicines have similar active ingredients. These ingredients can interfere with other treatments and also trigger significant side effects. Therefore, it’s essential to know what’s inside your dog’s heartworm medicine and work with your veterinarian to find one that’s safe for your dog.
Our guide contains thorough reviews of the best heartworm medicines as well as information on common active ingredients. Make sure to read through this guide so that you can find the best heartworm medicine for your precious pup.
A Quick Look at Our Favorites in 2023
Image Product Details
Best Overall
Heartgard Plus
Trusted over 2 billion times
Safe for pregnant dogs
Safe for Collies
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Best Value
Tri-Heart Plus Chewable
Affordable
Not many side effects
Delicious beef flavor
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Premium Choice
Simparica Trio
Delicious liver flavor
Also kills fleas and ticks
Doesn’t contain ivermectin
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Milbehart Flavored
Safe for 4-week-old puppies
Safe for cats
Safer for herding breeds
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Sentinel Spectrum
Safe for herding breeds
Additional protection against fleas
Also protects against whipworms and tapeworms
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The 10 Best Heartworm Medication for Dogs
Heartgard Plus Chew for Dogs is a chew that prevents heartworms and controls hookworms and roundworms. Each chew also contains real beef, so many dogs find them to be delicious treats that they get to eat once a month.
Active Ingredients: Ivermectin, pyrantel
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: Vomiting, diarrhea, depression/lethargy, anorexia, mydriasis, ataxia, staggering, convulsions, hypersalivation
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The formula is safe for puppies over 6 weeks old and pregnant dogs. Collies are often sensitive to the common active ingredients in heartworm medication, but clinical trials proved that Heartgard chews are safe for Collies to eat when given proper doses.
Heartgard has been a trusted brand for many years, and its heartworm chews have a great track record for maintaining customer loyalty. It’s a veterinarian-recommended brand and has been trusted over 2 billion times.
This medication isn’t without side effects. The most common symptoms include vomiting or diarrhea within 24 hours of consumption. If your dog experiences any side effects, make sure to contact your veterinarian right away.
Overall, Heartgard Plus Chew for Dogs is the best overall heartworm medicine for dogs because of its proven effective formula and delicious beef flavor, which makes administering it very easy. It’s also relatively affordable compared to its competitors.
Pros
Trusted over 2 billion times
Safe for pregnant dogs
Safe for Collies
Real beef flavoring
Affordable
Cons
Common side effects are temporary vomiting and diarrhea
Tri-Heart Plus heartworm chews have a formula that’s effective against killing heartworm larvae and treating and controlling roundworms and hookworms. The tablets are small in size, and they have a beef flavor to encourage dogs to eat them.
Trusted over 2 billion times
Safe for pregnant dogs
Safe for Collies
Real beef flavoring
Affordable
- Trusted over 2 billion times
- Safe for pregnant dogs
- Safe for Collies
- Real beef flavoring
- Affordable
Common side effects are temporary vomiting and diarrhea
- Common side effects are temporary vomiting and diarrhea
Active Ingredients: Ivermectin, pyrantel
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: Upset stomach, incoordination, convulsions, drooling
Some dogs rarely experience the listed side effects, so this chew is excellent for dogs with particularly sensitive stomachs. However, you do have to be careful when administering this chew to Collies and other herding breeds. Make sure you closely monitor them for at least 24 hours after administration of this treatment.
Tri-Heart Plus is also one of the most affordable options, so it’s the best heartworm medicine for dogs for the money that you pay.
Pros
Affordable
All treats roundworms and hookworms
Not many side effects
Delicious beef flavor
Cons
May not be safe for herding breeds
This premium heartworm chew goes beyond protecting your dog from heartworm. It kills fleas and five types of ticks, and it treats and controls roundworms and hookworms. Therefore, even though it’s one of the more expensive heartworm chew options, you can end up saving money because you don’t have to purchase separate flea and tick medication.
Affordable
All treats roundworms and hookworms
Not many side effects
Delicious beef flavor
- Affordable
- All treats roundworms and hookworms
- Not many side effects
- Delicious beef flavor
May not be safe for herding breeds
- May not be safe for herding breeds
Active Ingredients: Sarolaner, moxidectin, pyrantel
Age Range: Puppies 8 weeks and older
Administration Form: Oral
Possible Side Effects: Vomiting, diarrhea
The chews also have a liver flavor, so dogs typically enjoy eating them as monthly treats. Dogs can also take it with or without food, so administering this medicine is a rather convenient process.
As with all other heartworm medications, there are some side effects and medical conditions to consider before administering this chew. This medication’s most common side effect is an upset stomach, but it’s a fairly rare occurrence. It’s also an option to consider for herding breed owners because it doesn’t contain ivermectin.
However, keep in mind that this chew hasn’t been evaluated for pregnant or lactating dogs. It also contains sarolaner, which can trigger symptoms for dogs with a history of having seizures.
Pros
Administer with or without food
Delicious liver flavor
Also kills fleas and ticks
Doesn’t contain ivermectin
Cons
Not evaluated for pregnant and lactating dogs
Must use cautiously for dogs with a history of seizures
- Milbehart Flavored Tablets – Best for Puppies
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Active Ingredients: Milbemycin oxime
Age Range: Puppies 4 weeks and older
Administration Form: Oral
Possible Side Effects: Depression/lethargy, vomiting, ataxia, anorexia, diarrhea, convulsions, weakness, hypersalivation
Milbehart Flavored Tablets protect puppies and dogs against heartworms, hookworms, roundworms, and whipworms. Puppies as young as 4 weeks old can eat these tablets.
Administer with or without food
Delicious liver flavor
Also kills fleas and ticks
Doesn’t contain ivermectin
- Administer with or without food
- Delicious liver flavor
- Also kills fleas and ticks
- Doesn’t contain ivermectin
Not evaluated for pregnant and lactating dogs
Must use cautiously for dogs with a history of seizures
- Not evaluated for pregnant and lactating dogs
- Must use cautiously for dogs with a history of seizures
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Active Ingredients: Milbemycin oxime
Age Range: Puppies 4 weeks and older
Administration Form: Oral
Possible Side Effects: Depression/lethargy, vomiting, ataxia, anorexia, diarrhea, convulsions, weakness, hypersalivation
They also don’t contain ivermectin. Instead, they have milbemycin oxime, which is generally safe for herding breeds when given in moderate doses. So, they can be a safer alternative for herding breeds.
Milbehart tablets are also safe for cats, so they can be a convenient option for you if you have both cats and dogs in your home. For cats, these chews can remove adult hookworms and roundworms. They also prevent heartworm disease attributed to the species Dirofilaria immitis.
Although Milbehart tablets are safe for very young puppies, it does come with some significant side effects for hypersensitive dogs. Therefore, it’s absolutely crucial to administer the proper dosages and monitor your puppy’s condition for the first few times you administer the tablets
Pros
Safe for 4-week-old puppies
Safe for cats
Safer for herding breeds
Cons
Significant potential side effects
- Sentinel Spectrum Chew for Dogs
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Active Ingredients: Milbemycin oxime, lufenuron, praziquantel
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: Depression/lethargy, vomiting, ataxia, anorexia, convulsions, skin congestion, hypersalivation, pruritus, urticaria
Sentinel Spectrum Chew for Dogs provides protection against five different parasitic worms: heartworms, hookworms, roundworms, whipworms, tapeworms. It also prevents flea eggs from hatching. Therefore, although it tends to have a higher price than other heartworm medicine, it provides more comprehensive protection against parasites.
Safe for 4-week-old puppies
Safe for cats
Safer for herding breeds
- Safe for 4-week-old puppies
- Safe for cats
- Safer for herding breeds
Significant potential side effects
- Significant potential side effects
Active Ingredients: Milbemycin oxime, lufenuron, praziquantel
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: Depression/lethargy, vomiting, ataxia, anorexia, convulsions, skin congestion, hypersalivation, pruritus, urticaria
The chew’s formula contains active ingredients that are safe for herding breeds. However, it hasn’t been evaluated for pregnant or lactating dogs. Each chew has a beef flavor to encourage dogs to eat them. However, many customers have reported that their dogs don’t like the taste.
Most dogs can safely eat this medicine. However, since it does have several significant side effects, be extra cautious with dogs with hypersensitivities.
Pros
Safe for herding breeds
Also protects against whipworms and tapeworms
Additional protection against fleas
Cons
Not evaluated for pregnant or lactating dogs
Dogs don’t like the taste
- Advantage Multi Topical Solution for Dogs
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Active Ingredients: Imidacloprid, moxidectin
Age Range: 7 weeks and older
Administration Form: Topical
Possible Side Effects: localized pruritus, hematochezia, diarrhea, vomiting, lethargy, inappetence, pyoderma
If you’re struggling to find a heartworm chew that your dog likes, Advantage Multi Topical Solution is a considerable option because it’s a topical treatment. Instead of oral administration, you apply the formula between your dog’s shoulder blades.
Safe for herding breeds
Also protects against whipworms and tapeworms
Additional protection against fleas
- Safe for herding breeds
- Also protects against whipworms and tapeworms
- Additional protection against fleas
Not evaluated for pregnant or lactating dogs
Dogs don’t like the taste
- Not evaluated for pregnant or lactating dogs
- Dogs don’t like the taste
Active Ingredients: Imidacloprid, moxidectin
Age Range: 7 weeks and older
Administration Form: Topical
Possible Side Effects: localized pruritus, hematochezia, diarrhea, vomiting, lethargy, inappetence, pyoderma
Along with protecting your dog from heartworms, this treatment also kills adult fleas and treats and controls roundworms, hookworms, whipworms, and sarcoptic mange. Studies for this medicine also showed that it doesn’t interfere with many other treatments, including the following:
ACE inhibitors
Anticonvulsants
Antihistamines
Antimicrobials
Chondroppotectants
Corticosteroids
Immunotherapeutics
MAO inhibitors
NSAIDs
Ophthalmic medications
Sympathomimetics
Synthetic estrogens
Thyroid hormones
Urinary acidifiers
However, if your dog has sensitive skin, be extra careful with administering this medicine. It can cause some irritation, including pruritus.
ACE inhibitors
Anticonvulsants
Antihistamines
Antimicrobials
Chondroppotectants
Corticosteroids
Immunotherapeutics
MAO inhibitors
NSAIDs
Ophthalmic medications
Sympathomimetics
Synthetic estrogens
Thyroid hormones
Urinary acidifiers
- ACE inhibitors
- Anticonvulsants
- Antihistamines
- Antimicrobials
- Chondroppotectants
- Corticosteroids
- Immunotherapeutics
- MAO inhibitors
- NSAIDs
- Ophthalmic medications
- Sympathomimetics
- Synthetic estrogens
- Thyroid hormones
- Urinary acidifiers
Pros
Effective alternative for picky dogs
Kills adult fleas
Treats and controls sarcoptic mange
Doesn’t interfere with other treatments
Cons
Can cause skin irritation
- Trifexis Chewable Tablet for Dogs
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Active Ingredients: Spinosad, milbemycin oxime
Age Range: Puppies 8 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, itching, decreased activity, diarrhea, decreased appetite, redness of the ear
Trifexis Chewable Tablet for Dogs has a powerful formula that disrupts the heartworm life cycle and kills fleas. It’s also effective against hookworms, roundworms, and whipworms.
Effective alternative for picky dogs
Kills adult fleas
Treats and controls sarcoptic mange
Doesn’t interfere with other treatments
- Effective alternative for picky dogs
- Kills adult fleas
- Treats and controls sarcoptic mange
- Doesn’t interfere with other treatments
Can cause skin irritation
- Can cause skin irritation
Active Ingredients: Spinosad, milbemycin oxime
Age Range: Puppies 8 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, itching, decreased activity, diarrhea, decreased appetite, redness of the ear
Clinical tests show that this formula doesn’t trigger severe side effects. It’s also a safe option to consider for herding breeds. However, it isn’t meant for young puppies, and you should wait until your dog is at least 8 weeks old before administering this medicine.
The formula also contains artificial beef flavoring, which can be delicious for some dogs. Unfortunately, many dogs aren’t fooled by the flavor, and you might have to mask the chew with pill pockets or other delicious snacks, such as peanut butter.
Pros
Mild side effects
Also kills fleas
Safe for herding breeds
Cons
Not for young puppies
Dogs don’t like the taste
- Selarid Topical Solution
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Active Ingredients: Selamectin
Age Range: Puppies 6 weeks and older
Administration Form: Topical
Possible Side Effects: Localized alopecia, vomiting, loose stool or diarrhea, anorexia, lethargy, salivation, tachypnea, muscle tremors.
Selarid Topical Solution is a broad-spectrum topical treatment that fights against heartworm disease, fleas, ear mites, mange, and ticks. Since it’s a topical treatment, it’s a great option to try on dogs with picky tastes. Just remember that topical treatments can cause localized skin irritation, so be extra cautious if your dog has sensitive skin.
Mild side effects
Also kills fleas
Safe for herding breeds
- Mild side effects
- Also kills fleas
- Safe for herding breeds
Not for young puppies
Dogs don’t like the taste
- Not for young puppies
- Dogs don’t like the taste
Active Ingredients: Selamectin
Age Range: Puppies 6 weeks and older
Administration Form: Topical
Possible Side Effects: Localized alopecia, vomiting, loose stool or diarrhea, anorexia, lethargy, salivation, tachypnea, muscle tremors.
The active ingredient is selamectin, which doesn’t cause any particular adverse effects on herding breeds. It’s also very rare for dogs to experience side effects. This formula is also safe for cats, so if you have multiple pets in your home, make sure to consider this option.
Pros
Great alternative for picky dogs
Also treats fleas ear mites, mange, and ticks
Rare occurrences of side effects
Safe for cats
Cons
Can cause localized skin irritation
- Interceptor Plus Chew for Dogs
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Active Ingredients: Selamectin
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, diarrhea, depression/lethargy, ataxia, anorexia, convulsions, weakness, salivation
Interceptor Plus Chew for Dogs is a monthly chew that protects your dog against heartworm infestations, and it also treats and controls adult roundworms, hookworms, whipworms, and tapeworms.
Great alternative for picky dogs
Also treats fleas ear mites, mange, and ticks
Rare occurrences of side effects
Safe for cats
- Great alternative for picky dogs
- Also treats fleas ear mites, mange, and ticks
- Rare occurrences of side effects
- Safe for cats
Can cause localized skin irritation
- Can cause localized skin irritation
Active Ingredients: Selamectin
Age Range: Puppies 6 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, diarrhea, depression/lethargy, ataxia, anorexia, convulsions, weakness, salivation
The chew is also infused with delicious chicken flavoring to encourage your dog to eat it. Your dogs can eat it as a treat, your cat can mix it with their food.
These chews are a great broad-spectrum treatment against common intestinal parasites. However, it’s important to note that they’re not safe for puppies under 6 weeks old and pregnant or lactating dogs.
Pros
Also treats against tapeworms
Delicious chicken flavor
Can mix with food
Cons
Not for lactating dogs
- Iverhart Max Chew for Dogs
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Active Ingredients: Ivermectin, pyrantel pamoate, praziquantel
Age Range: Puppies 8 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, diarrhea, depression/lethargy, ataxia, staggering, anorexia, convulsions, mydriasis, hypersalivation
This broad-spectrum chew is soft and easily digestible, and it also has an enticing bacon flavor. Along with protecting your dog against heartworm disease, it also treats and controls roundworms, hookworms, and tapeworms.
Also treats against tapeworms
Delicious chicken flavor
Can mix with food
- Also treats against tapeworms
- Delicious chicken flavor
- Can mix with food
Not for lactating dogs
- Not for lactating dogs
Active Ingredients: Ivermectin, pyrantel pamoate, praziquantel
Age Range: Puppies 8 weeks and older
Administration Form: Oral
Possible Side Effects: vomiting, diarrhea, depression/lethargy, ataxia, staggering, anorexia, convulsions, mydriasis, hypersalivation
The medication can potentially cause several different side effects, and it hasn’t been evaluated for pregnant or lactating dogs. It also contains ivermectin, so if you have a herding breed, you have to be extra careful about the dosage or avoid administering it at all.
Although the chews are marketed as soft, some customers have reported that the packaging doesn’t adequately contain the chews’ moisture and dries them up.
Pros
Bacon flavored
Also treats against tapeworms
Chewy and easily digestible
Cons
For older puppies
Not for herding breeds
Some packaging dries up chews
Bacon flavored
Also treats against tapeworms
Chewy and easily digestible
- Bacon flavored
- Also treats against tapeworms
- Chewy and easily digestible
For older puppies
Not for herding breeds
Some packaging dries up chews
- For older puppies
- Not for herding breeds
- Some packaging dries up chews
Buyer’s Guide: How to Choose the Best Heartworm Medicine for Your Dog
Still not sure which heartworm medication is the right one for your pup? We’ll help you narrow in on the top choice based on these important variables highlighted below.
Active Ingredients
Heartworm medicines use several common active ingredients. It’s essential to be well-informed about these ingredients because dogs can have allergies or other sensitivities. Some of these ingredients can also have severe side effects.
When shopping for heartworm medicine for dogs, you’ll most likely come across the following ingredients.
Ivermectin
Ivermectin is one of the most common active ingredients in heartworm medicine. It can also treat other intestinal parasites and mites.
This ingredient doesn’t typically cause any side effects when you give proper dosages to your pets. The most common side effect is an upset stomach.
It’s important to remember that herding breeds, such as Collies, can have an ivermectin sensitivity due to a genetic mutation. This mutation is individualized, so it’s not in all herding breed dogs.
Ivermectin also interferes with some treatments, such as the following:
ketoconazole
Itraconazole
Cyclosporine
Erythromycin
Amlodipine besylate
Make sure to let your veterinarian know of any other medications your dog takes.
ketoconazole
Itraconazole
Cyclosporine
Erythromycin
Amlodipine besylate
- ketoconazole
- Itraconazole
- Cyclosporine
- Erythromycin
- Amlodipine besylate
Milbemycin Oxime
Milbemycin oxime is another standard preventative treatment against heartworms and other internal parasites. It’s also often combined with flea medication to develop a broad-spectrum formula for dogs.
This ingredient is usually administered orally, and dogs can take it with or without food. If your dog experiences an upset stomach, try serving it with some food.
Milbemycin oxime can interact with other drugs, including cyclosporine, amiodarone, diltiazem, azole antifungals, and erythromycin. It can also interfere with some vitamins and supplements.
Pyrantel
Most heartworm medications don’t exclusively fight against heartworms. They often include other dewormers for other internal parasites. Pyrantel is a common active ingredient that gets integrated with ivermectin. It’s a dewormer that treats roundworm, hookworm, and other stomach worms.
Side effects aren’t too common, but they include vomiting, nausea, lack of appetite, and diarrhea. Vomiting can occur due to an empty stomach, so it’s safe to give this medication with food. Along with vomiting, diarrhea and a lack of appetite can be due to parasites getting eliminated from the body.
Pyrantel is often safe for pregnant and nursing animals, but you must be extra mindful of administering the proper dosage. Some pets can also be allergic to it. It interferes with several other drugs including levamisole, morantel, piperazine, and organophosphates.
Selamectin
Selamectin is an antiparasitic that treats heartworms, fleas, ear mites, scabies, and some ticks. It’s administered topically on unbroken skin. Since it’s topical, it’s important that dogs don’t get a bath within 2 hours of contact.
This ingredient is often safe for pregnant dogs. However, similar to ivermectin, herding breeds can be extra sensitive to it.
Selamectin can interfere with other medications:
Amiodarone
Carvedilol
Clarithromycin
Cyclosporine
Diltiazem
Erythromycin
Itraconazole
Ketoconazole
Quinidine
Spironolactone
Tamoxifen
Verapamil
Moxidectin
Moxidectin can be administered orally and topically. It’s an antiparasitic that treats intestinal worms and mange on top of heartworms. It’s also often combined with imidacloprid to treat fleas. When administered topically, make sure not to bathe your dog for the next 4 days.
Amiodarone
Carvedilol
Clarithromycin
Cyclosporine
Diltiazem
Erythromycin
Itraconazole
Ketoconazole
Quinidine
Spironolactone
Tamoxifen
Verapamil
- Amiodarone
- Carvedilol
- Clarithromycin
- Cyclosporine
- Diltiazem
- Erythromycin
- Itraconazole
- Ketoconazole
- Quinidine
- Spironolactone
- Tamoxifen
- Verapamil
Side effects are uncommon. However, some dogs with milbemycin sensitivities can experience fatal symptoms with moxidectin. Therefore, it’s imperative to consult with a veterinarian before using moxidectin.
There aren’t any reports of moxidectin interfering with specific medications. However, it should be administered with caution if your dog is on a benzodiazepine treatment.
Conclusion
Based on our reviews, Heartgard Plus Chew for Dogs is the best heartworm medication because it has a potent formula. It also has a proven track record that effectively protects dogs against heartworm disease. Simparica Trio is another great option because it provides broad-range protection against many parasites.
Overall, the most important thing you can do for your dogs is to understand the active ingredients in heartworm medicine and work with your veterinarian to find the safest option for them. Heartworm medicine is essential to dogs’ health, and it can greatly increase dogs’ lifespans and improve their quality of life.
Featured Image Credit: ThamKC, Shutterstock
