Your dog is a member of the family, and as such, you make sure to do everything possible to keep it healthy and happy. This includes finding the best heartworm prevention medication. Without proper medication, it is tough to protect your pup from this terrible disease.

There are many options on the market. What one person may feel is the best heartworm prevention medication, another may not, and even professionals may recommend different medications than each other. Therefore, when trying to find what will work for your dog, you need to do some research into your choices so you can make an educated decision.

Information to Keep in Mind

vet checking a dog's foot

Image via flickr

Choosing any medication for your pup is an important decision just as with picking a high-quality dog treat. You have to be sure that you do not pick something that could harm your pet.

To help make choosing the best heartworm prevention easier, here are some frequently asked questions which provide some in-depth information.

What is heartworm?

The American Heartworm Association defines this condition as a disease where heartworms live inside the major organs, such as the lungs and heart, in addition to getting into the blood vessels of a mammal.

The worms cut off the blood supply, which leads to serious health problems and eventually death. Dogs get this disease through mosquito bites.

This is a serious condition for dogs because the worms can live their whole life cycle inside a dog’s body. They can reproduce rapidly, leading to a severe infestation. This is why dogs must have heartworm prevention medication.

What ingredients are in heartworm meds?

There is a lot of talk about medications given to dogs and how they could cause adverse reactions.Some people worry giving a dog heartworm medication is damaging to the dog. However, according to Belvoir Publications, experts agree that the risks of not giving your dog heartworm preventative are more serious than the risks of giving your dog the medication.

With that in mind, not every heartworm medication is equal when it comes to ingredients. You could compare this to how not every dog collar is equal even if they look similar. Because of this, you need to know the ingredients in a medication.

Ivermectin and milbemycin oxime are active ingredients in some of the best selling medications. They are generally safe for use with minimal adverse effects. Another option that is safe for dogs is diethylcarbamazine or DEC.

The main issue with DEC is that a dog cannot have heartworm when taking the medication because it could cause death. You also must give DEC every day to maintain protection.

Some heartworm medications may also contain ingredients to protect against fleas and ticks, which could have additional side effect risks.

When should I give my dog heartworm meds?

There are different schools of thought about this because some experts think overuse could lead to resistance.

However, think about it this way: do you only put an ID dog tag on when you think your pet could go missing or do you put it on all the time just to be safe?

The chances are you keep it on all the time as a precaution. You should do the same thing with heartworm medication and use it all year as the prevailing experts recommend.

We Know Our Stuff

Man in military is injecting some medicine to dog's mouth while the owner of the dog is holding the head

Image via flickr

To bring you only the best heartworm prevention medications, we made sure to do our due diligence during the research process. We talked with veterinarians, read expert opinions, and sifted through consumer reviews to bring you unbiased reviews. We feel the list below is an excellent representation of the best options on the market.

Costs for Heartworm Prevention Medications

Heartworm medication is generally not too expensive. Like all dog medications, though, the price is dependent on the size of your dog. Larger dogs cost more to medicate because they require higher doses. In addition, the brand you buy will affect cost.

5 Best Heartworm Prevention Medications

The following is a rundown on the five best heartworm prevention medications on the market. Keep in mind when buying that you must have a prescription from your veterinarian to purchase these medications.

Heartgard Plus

This chewable heartworm prevention medication provides your dog with protection against roundworms and hookworms in addition to heartworms. They have a beef flavor and include real beef as an ingredient. You will give your dog one chewable each month, starting at the age of six weeks.

Heartgard Plus contains ivermectin and anthelminthic. There is a warning that this medication may not be suitable for herding breeds. Also, it is crucial that a dog chews the pill and does not swallow it whole.

They feel it is an exceptionally effective medication that provides reliable protection for dogs. Customers note that their dogs love the beefy flavor and enjoy taking the medication. One consumer did note that the medication can cause staining of white fur if the dog licks itself shortly after taking it.


Unlike all the other best heartworm prevention medications on our list, Revolution is a topical treatment. It is also a combination medication that protects against ear mites, mange, ticks, and fleas. It is for use in dogs six weeks and older.

This once-a-month treatment contains selamectin as an active ingredient. It is safe for lactating and pregnant dogs with a chance of side effects occurring in less than one percent of all users. There is a warning that dosage amounts in herding breeds must be exact to prevent adverse reactions.

They like that it is topical, which is especially helpful if a dog does not like to take pills or chewables.

Consumers also say it is a highly effective medication that works well to prevent both heartworm and fleas. Some users did note that the medication may cause itching or sensitivity at the application site.


Sentinel is another combination medication that treats not only heartworm but also fleas, hookworms, and whipworms. It is important to note that this medication will not kill adult fleas. It only prevents the development of eggs.

You may use this on dogs over four weeks old weighing at least two pounds. It comes in chewable tablets for once-a-month administration.

Sentinel contains milbemycin oxime and lufenuron as active ingredients. Side effects that may occur include seizures, loss of appetite, vomiting, drowsiness, hives, diarrhea, weakness, depression, and itching.

They say it is highly effective in preventing heartworm and keeping flea infestation down.

Many customers are long term users of this product and say it is an excellent option for herding breeds that are sensitive to other medications. However, some users said it was not very effective at flea or hookworm prevention


Another tablet option, Interceptor provides a choice in the best heartworm prevention, along with protecting against hookworms, roundworms, and whipworms. It is a once-a-month treatment for dogs over the age of four weeks, weighing more than two pounds.

The main ingredient is milbemycin oxime, which means it has the same possible side effects as Sentinel. It also is a good alternative for herding breeds that cannot take other heartworm prevention medications.

Consumers like that the pill is small, which means it great for picky dogs who won’t take chewables. They also say it is effective against treating heartworms, but some users voice concerns that it does not protect against hookworms very well.

Iverhart Max

Iverhart Max offers full protection against heartworm, tapeworm, roundworm, and hookworm infestations. You can give to your dog over the age of eight weeks that weighs at least six pounds once a month. It has a pork liver base with beef flavoring added to make the soft chewable tablet palatable.

The main ingredient is pyrantel pamoate, which is a dewormer. Experts do not recommend this heartworm medication for herding breeds due to potentially harmful side effects. You also should not use this medication if your dog has taken another heartworm medication or if it is pregnant or lactating.

They say it works well at keeping their dogs heartworm free and also is effective at treating the other types of parasites as claimed. The most common complaint is that dogs do not want to chew the treat because they do not like the taste.

Presenting the Best of the Best

From our research and personal experience with the best heartworm prevention medications, we feel the choices on our list are the best possible options on the market. We feel each offers top-notch protection to keep your dog heartworm free.

When choosing a medication, you should pay attention to administration. As you probably know, half of the battle of medicating your dog is getting it to actually take the medication, so you need to find an option that works for your dog. In addition, since many of the medications use ingredients that experts do not recommend for certain breeds, you should keep that in mind when making your final choice.

Tell us which of the best heartworm prevention medications you prefer and share your experiences with your chosen medication in the comments below.

Featured Image: Image by David Mark from Pixabay