Dog sick with heartworm

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Heartworm disease is a worrisome infection that could target your dog’s wellbeing and quality of life. When left untreated, the disease can cause a variety of health issues, lead to organ damage, and even cause death in affected dogs. Due to these reasons, it is incredibly important for you to know how to lower the risk of this infection and help your dog live a happier and healthier life. 

Fortunately, doing so is not difficult at all. With a little care and some key information regarding heartworm medicine for dogs, you can boost your chances of protecting your dog against the condition and keeping larger risks at bay. To help you through this path, here is a lowdown on the best medicine for heartworm disease.

Best Types Of Heartworm Medicine For Dogs

There are two different approaches to heartworm medicine for dogs, depending on your pet’s health and other factors: preventative medicine and curative care. Many vets consider preventative prescriptions to be the best form of heartworm medicine for dogs as it keeps infections from occurring in the first place. 

Below we’ll take a look at the different forms of preventative heartworm medicine: topical, oral, and injectable formulas.

Graphic listing types of preventative heartworm medicine for dogs

Preventative Heartworm Medicine For Dogs

1. Topical heartworm medicine

This group of medicine is applied once a month as a topical solution. By applying a small amount of this medication over the back of your dog’s neck, you can increase their ability to ward off heartworm infections and eradicate immature parasites before they get the chance to grow. 

Two popular examples in this category include Revolution (active ingredient: selamectin) and Advantage Multi (active ingredients: imidacloprid, moxidectin).

While using these topical medications, ensure that you are utilizing them with the help of a qualified vet. This helps ensure that your dog steers clear of side effects or contraindications while taking these medications.

2. Oral heartworm medicine

If you don’t have problems giving your dogs oral medication, you can also explore these options for your pet. This treatment is administered on a monthly basis and kills small heartworms before they start creating problems for your dog.

Popular treatments in this segment include Sentinel (active ingredients: milbemycin oxime and lufenuron) and Heartgard Plus (active ingredients: ivermectin and pyrantel). 

Some oral medications are more suitable for dogs of a certain age, which makes it important that you consult with an experienced vet before you start on a preventative regime.

Sentinel for Dogs - 6 months (Rx)

Sentinel is a preventative prescription that arms your pet against heartworms, adult roundworms, adult hookworms, whipworms, and the development of flea eggs. This preventative heartworm medicine is administered monthly via a flavored chewable tablet.

3. Injectable heartworm medicine

This heartworm medication approach is considered the most convenient due to its period of effectiveness. Where topical and oral medications protect your dog for a month after the dosage, injectable heartworm prevention medicine can work for a full 12 months. 

ProHeart 12 (active ingredient: moxidectin) is the most popular and widely used treatment in this segment. When this medication is inserted under the skin and into the fat-storing tissue, it works as a slow-dissolving medicine that could protect your dog for the outlined period.

In order to use this medication, you need to consult with a qualified vet. This also ensures that you are steering clear of possible side effects that may occur in dogs with some pre-existing conditions.

What Is Heartworm Disease?

Heartworms or Dirofilaria immitis are parasites that enter the bloodstream of different mammal species through mosquitoes. When a mosquito bites an infected mammal, it contracts microfilariae or heartworm larvae. Afterwards, a carrier mosquito can transfer those larvae into another mammal by biting them. 

If  a mosquito carrier bites a dog, it pushes the heartworm larvae into their bloodstream. When left untreated, these larvae turn into fully-grown worms. These worms can reside inside blood vessels that lead to the heart and lungs resulting in an obstruction, which can often lead to coughing and wheezing along with other symptoms.

In advanced cases of the infection, these parasites travel to the heart and cause further complications such as heart failure and grow into significant problems. But even when these parasites remain within blood vessels, they can affect blood flow and cause a variety of health issues1

If a heartworm dies inside of an infected dog’s body, it triggers a toxic and potentially fatal reaction. Because of these risks, preventing such complications through the best heartworm medicine for dogs is a priority for every responsible pet parent.

You can also look at the heartworm lifecycle to understand these infections in a better manner:

  • A mosquito feeds on an infected dog and contracts microfilariae. 
  • Within 1-14 days, the microfilariae turn into infective larvae inside the mosquito.
  • The mosquito bites an uninfected dog and transfers the larvae into them.
  • Within 6-7 months, the larvae turn into fully-grown heartworms and live inside the infected dog’s heart.
  • Some of these larvae may transfer into uninfected mosquitoes whenever they bite the infected dog.
  • The cycle continues.

It is crucial to remember that a single dog can be infected with different heartworms at once and simultaneously experience varying stages of heartworm disease. This calls for a holistic approach to manage heartworm infections and related symptoms such as coughing and difficulty breathing. 

Graphic listing Class 1-4 heartworm symptoms


There are several signs of heartworm disease that could tell you about the existence of a parasitic infection in your dog. With that being said, you should keep in mind that most of these symptoms are only visible in the advanced stages of the disease. That is why, if you notice even a single sign of heartworm disease, it is better to reach out to a veterinarian and discuss your dog’s condition with them before it’s too late. 

Heartworm disease is categorized into four different classes2. In turn, the expected symptoms are also distributed among them:

  • Class 1. This stage shows limited to no symptoms. Mild and occasional cough is often the only sign of heartworm disease at this stage. 
  • Class 2. Mild symptoms such as more constant cough or tiredness after activity become apparent. This makes it easier to detect these signs.
  • Class 3. Moderate to severe symptoms such as frequent cough and lethargy without activity become more visible. Difficulty breathing, weight loss, loss of appetite, coughing up blood, and sickly appearance are common parts of this class.
  • Class 4. This class is also called Caval Syndrome, where heart valves get blocked by the presence of heartworms. In this stage, severe symptoms of heart failure such as physical shock or collapse become evident. In addition to warning signs such as bluish discoloration of skin and gums, these signs are often accompanied by symptoms from Class 3.

While the advanced classes of heartworm disease paint a bleak picture, your dog does not have to reach these stages after a heartworm infection. With timely treatment as well as preventative measures, you can reduce the chance of your dog being affected by more serious symptoms of heartworm disease. By learning what the best heartworm medicine is for dogs, you may save your dog from painful complications and give them a happier life ahead.

Graphic listing heartworm diagnosis methods


Because many dogs experience little to no symptoms during the earliest stage of heartworm disease, the diagnosis of heartworm infections can be a bit tricky. While the antigen detection test is widely popular for detecting heartworms and their parasitic actions in an infected dog’s body, this test does not detect early-stage infections.  

This is because the antigen detection test can only identify adult parasitic worms that have had time to grow within the pet’s body. If you perform early-stage tests, younger and smaller worms can easily evade the diagnosis. That is where your veterinarian can perform other diagnostics such as chest X-rays, echocardiography, and different blood tests. This allows them to determine which heartworm medicine is right for your dog. 

So is heartworm medicine necessary for dogs going through the early stages of infections? It certainly is due to its targeted treatment effects. When you obtain heartworm infection medication through an in-person checkup or online vet prescription, you can reduce greater risks to your dog’s health. 

Since these medications are easily available through different pharmacies, the level of accessibility ensures that you can follow the prescribed treatment method without any difficulties. 


In order to treat your dog’s heartworm disease, your vet will need to perform a series of diagnostic tests. This way, they can offer treatment options that are suitable for the current condition and symptoms that your dog exhibits at the time of checkup. 

These tests may include but are not limited to: 

  • Medical history review
  • Antigen detection test
  • Chest X-rays
  • Blood tests
  • Echocardiography
  • Visual or physical examination 

By taking a comprehensive approach, your veterinarian makes sure that any symptoms that coincide with other diseases could be ruled out while choosing a suitable treatment for your dog. For instance, if your dog has a history of respiratory issues, their difficulty in breathing symptoms may not be indicative of advanced heartworm infection. But if your dog has not had any major health issues prior to being infected by heartworms, your doctor may choose a more targeted approach for any symptoms they are presenting now.  

The factors that influence the suggested treatment regimen include but are not limited to:

  • Current as well as previous diseases and conditions
  • Number of heartworms present across blood vessels and organs
  • Physical condition or damage caused by heartworms

At advanced stages of heartworm infection, your veterinarian may first focus on stabilizing the heart rate and breathing issues of your dog before beginning treatment for heartworm disease. This approach increases the chances of recovery for your dog.

When it comes to targeted treatment of active heartworm infection, there is only one drug called melarsomine dihydrochloride that is available for this purpose. This heartworm medicine for dogs comes in an injectable composition. 

While using this treatment, your veterinarian may suggest either of the following dosage methods:

  1. A 2-dose method that is injected 24 hours apart.
  2. A 3-dose method that has a month’s difference between the first and second doses, and a 24-hour difference between the second and third doses. 

The dosage depends on a case-to-case basis. But many veterinarians suggest the 3-dose method due to its overall efficacy and safety profile.

With that being said, if you want to keep your pet entirely safe from heartworm infections, preventative medications are the most popular approach3. Since these medications protect your dog from heartworm infections from the get-go, they remain a highly advised approach by vets. They are also available in different forms, which makes them a sought-after solution by pet parents.Pet parent administering heartworm medicine to their dog

Pet parent administering heartworm medicine to their dog

Final Notes

Heartworm disease is a worrisome and potentially fatal condition that calls for the utmost care by pet parents. In addition to ongoing preventative measures, you also need to get immediate treatment at the first sign of heartworm infection. This makes sure that your dogs remain as healthy and happy as they deserve to be. 

At Dutch, we make it easier for you to get in touch with licensed veterinarians in your state. In case you need access to pet medication such as preventative medicine, a consultation with available vets can help you determine whether it would be a suitable approach for your dog in the first place. 

With affordability, convenience, and high-quality solutions, Dutch is here to help you take care of your pets without any compromise. To see how our solutions can assist you in becoming a better pet parent, don’t hesitate to browse through our platform today.



  1. Heartworm Disease in Dogs. By Clarke E. Atkins, et al. “Heartworm Disease in Dogs - Dog Owners.” Merck Veterinary Manual. June 2018. 

  2. “Keep the Worms Out of Your Pet’s Heart! The Facts about Heartworm Disease.” U.S. Food and Drug Administration..August 2019.  

  3. “What Are the Options for Heartworm Prevention for Dogs?” By Jennier Coates, et al. PetMD. July 2019. 

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Frequently Asked Questions

Who is Dutch?

Dutch is an online veterinary pet telehealth service, created by pet parents and board-certified veterinary specialists. We use a science-backed approach to provide pets relief for their everyday physical and behavioral health issues. Dutch connects you with licensed veterinarians over video chat and messaging to help you get care for your dog or cat quickly wherever you are — without the stress or expense of a vet visit. We also partner with pharmacies who can deliver prescription medication (in applicable states only) and over-the-counter treatments directly to your door. Dutch isn’t a veterinary practice or pharmacy, but a company that helps facilitate these services for pet parents to make veterinary care more accessible to all.

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