The Best Heartworm Medicine (Top 5 Choices for 2023)

A heartworm infection can cause serious health conditions in dogs, including lung disease, organ damage, heart failure, and even death. Cats and ferrets are also susceptible to heartworm disease. It’s caused by Dirofilaria immitis, a parasitic worm, and the worms are spread by mosquitoes.

More on this in a bit...

The disease develops quickly and animals infected with it can develop a cough, experience blood loss and even die, which is why protecting your dog with heartworm medicine is crucial. We'll get back to this later...

Prevention is definitely better than the cure in the case of this disease, which is why finding the best heartworm prevention for dogs is vital. There is a wide range of medicines available and the choice is not a simple one. So today we review the best medicine for the heartowm for your beloved pup.

At a Glance: Our Choices for Heartworm Medicine





Tri-Heart Plus

Tri-Heart Plus


Heartgard Plus Chewables

Heartgard Plus Chewables


Sentinel Spectrum

Sentinel Spectrum

For Intestinal Worms



Beef Flavor



Topical Ointment

The American Heartworm Society recommends monthly maintenance treatment all year round as prevention of serious infection. But before you start with any programs check with your vet first. Some medicines can only be given to dogs over a certain age, others have side effects and a few need a prescription.

The best heartworm treatment for dogs is usually the flea and heartworm combinations that not only prevent heartworms, they also protect your pet from fleas, intestinal parasites, ticks, and mites.

Product Reviews

Tri-Heart Plus

Tri-Heart Plus is administered on a monthly basis and prevents heartworm, roundworm, and hookworm. It’s an affordable and effective treatment against common parasites and has a pleasant beef flavor, so dogs don’t mind it too much.

The medication is safe for pups six weeks and older but they must be dewormed before taking it. For it to be effective, Tri-Heart Plus must be given the same time every month. Consult your vet if your dog experiences any of the following side-effects:


  • Convulsions
  • Vomiting
  • Anorexia
  • Diarrhea
  • Hypersalivation mydriasis
  • Staggering

Tri-Heart Plus is FDA-approved and good value for money.

Heartgard Plus Chewables

Heartgard Plus is a chewable tablet that’s given to your dog once a month. It eliminates hookworms, roundworms as well as heartworms and is FDA approved.

The tablet can be given once a month all year round or you can administer it during mosquito season. There is a beef flavor tablet and an unflavored one and it’s best to break the pill into your dog’s food. Swallowing it whole reduces its effectiveness and your pup could choke on it.

Before you start this program your dog must be checked for heartworm infestation and you mustn’t exceed the recommended dose. Dilated pupils, tremors, blindness, loss of appetite, and weight and disorientation are symptoms of an overdose.

Sentinel Spectrum

As far as medicines go, dogs will like the beefy flavored Sentinel Spectrum chewable tablets. There are three active ingredients: praziquantel, lufenuron, and milbemycin oxime that controls intestinal worms, fleas, and heartworms. An insect growth regulator also works to kill flea eggs and stops larvae growing into adult fleas.

There are six tablets in a box and these are given once a month, either mixed into your dog’s food or as a treat. Because it works according to your dog’s weight, it’s important you weigh him before starting the treatment.

Puppies, for example, will get one chewable tablet from the green box, which is for dogs between 8.1 up to 25 pounds and bigger dogs, between 50.1 to 100 pounds, will be given a chew from the blue box.

For improved efficacy, the tablet must be given with a meal or straight after.


Trifexis is possibly the best heartworm medication for dogs, but it comes at a price. It’s also beef flavored and it can be given to puppies as young as eight weeks old and they weigh more than five pounds. Because this particular medicine contains both milbemycin oxime and spinosad, you need a prescription from your vet.

Spinosad is an insecticide that kills fleas before they lay eggs and starts working within 30 minutes. Milbemycin oxime is an antiparasitic that’s effective against whipworms, hookworms, heartworms, and roundworms.

Trifexis is a beef flavored chewable tablet that kills and prevents infestations while protecting against heartworm, adult hookworm, adult roundworm, adult whipworms, and fleas. It is a once-a-month medication you can give to your dogs and puppies as young as 8 weeks old and weighing 5 lb or more.

If your dog has epilepsy you need to be cautious with this medication and if your dog experiences diarrhea, coughing, excessive drooling, or a decrease in his appetite or activity you need to consult your vet. This is also one of the most expensive heartworm medicines


Out of all the heartworm medicines featured, Revolution is the only topical ointment. This is administered monthly and protects against ear mites, fleas, American dog tick and sarcoptic mange. The topical parasiticide dries quickly and doesn’t leave a greasy area on your dog’s coat or skin.

You apply it at the base of your pet’s neck and as it works into the skin, the ingredients are distributed to provide month-long protection against heartworm and other parasites.

As a heartworm prevention medication, Revolution is FDA approved and safe for use. You just apply it to the base of your dog’s neck for month-long protection. As the medicine seeps into your pet’s skin, it distributes the medication providing lasting protection against different kinds of parasites.

It’s affordable and effective; however, there are some side effects. If your dog shows any signs of hair loss and skin irritation, quicker than normal breathing and excessive drooling, see your vet as soon as possible.


The importance of heartworm prevention can’t be stressed enough and the right treatment will also reduce the risk of other parasitic infestations. As a responsible pet owner, you need to make sure your dog has regular visits to the vet to keep him healthy and safe.

This video shows the infestation and cycle of heartworm in your pup:

If your pet is diagnosed with heartworms, your veterinarian will prescribe a treatment protocol that must be completed before giving your pet any type of heartworm preventative.

Unfortunately, there is no definitive treatment protocol available for cats but there are several palliative options including surgery in extreme cases. Heartworm treatment can be harsh, expensive, and traumatic for your pet's health. This is why comprehensive heartworm prevention is so very important.


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