How To Treat Heartworms With Ivermectin

Pet-Bandanas is a reader supported site. When you buy through links on our site, we may earn an affiliate commission. Product prices are the same whether you buy through our links or not. Thank you for being a part of our community. Learn More

The thought of your pet being infected with heartworm is a scary thing. It’s especially scary because most veterinarian offices have plastic models of heartworm-infected hearts sitting on their reception counters. It looks awful and the thought of your dog suffering through this sort of thing tears on your own heartstrings.

The fact is though is that heartworm is treatable even if you’ve never given your dog any preventative medication for it. And, although some dogs have been known to die from it, it is a very rare occurrence. As with any pet illness, a strong immune system will help a dog to fight off this dreadful affliction.


So what are the symptoms of heartworm? Heartworm infection is actually tricky to detect without a blood test. Symptoms can include lethargy, loss of appetite, weight loss, coughing, diarrhea or vomiting. These symptoms are common with many ailments so you won’t know for sure until you take your dog to the vet to test his blood.

Unfortunately for pet owners, dogs do not show clinical signs of infection until the heartworms reach their mature stage. Some dogs may show very few symptoms even after the heartworms have reached maturity. These dogs typically have a light infection and an inactive lifestyle. The symptoms of a heartworm infection include coughing when exercising, early exhaustion during exercise, severe weight loss, fainting, coughing up blood, and, eventually, congestive heart failure.

How Do Dogs Get Heartworms?

How To Treat Heartworms With Ivermectin
Source: Wikimedia Commons

Heartworms are parasitic roundworms that infect an animal’s heart and, if left untreated, will lead to congestive heart failure. They spread from host to host via mosquito bites. While they typically infect dogs, they have also been known to infect cats, wolves, coyotes, foxes, ferrets, sea lions, and even humans. Ferrets, sea lions, and humans are rarely infected.

The occurrence of heartworms used to be confined to the southern portion of the United States but has since spread to the rest of the country. Infections have been known to take place in all states except for Alaska. The parasites have also been found in Southern Europe, Asia, and Australia.


Before an infected dog can be treated to get rid of the heartworms, the dog must be evaluated based on kidney, liver, and heart function. This is done to evaluate all of the risks of treatment. Once the dog has been evaluated, the worms are typically killed off with an arsenic-based compound. Following this treatment, the dog must remain quiet for the next couple of weeks. This is done to ensure that the worms are safely dealt with by the dog’s body rather than breaking loose and leading to respiratory failure.

Treatment typically takes several weeks. After the mature worms are killed, the second type of treatment is started which is meant to kill off the immature heartworms. Treatment is considered finished and a success when the tests for heartworms show nothing.

If you discover that your pet has been infected with heartworms, your vet will have a treatment program that he or she will recommend but it is very costly and can sometimes result in the death of your dog because the medication itself is toxic. This is where if you have pet dog insurance, you will be grateful. You may also wish to explore more natural alternatives to heartworm treatment or even prevention if your dog is not already infected. One natural herbal remedy for the purpose of preventing heartworm is Black Walnut. It comes in a tincture and you can add a few drops to your dog’s water dish as an effective prevention. The amount and frequency of the dosage will depend on the size of your dog.

Heartworms are transmitted by mosquitoes just like many other infectious diseases. So, giving your dog heartworm medication during the winter months is not necessary if you live in a climate where the temperature drops below freezing in winter. During the summer months, however, your dog may be at greater risk from contracting this infection and so you may want to consider giving your pet some sort of preventative medication such as Revolution or Heartgard.


Revolution comes in little liquid vials and it is poured onto the dog’s skin at the back of their neck. It soaks into the skin and into the bloodstream. It is actually an all-in-one treatment for fleas ticks and heartworms.


Heartgard  (ivermectin), on the other hand, comes in pill form. You generally need to give your dog his medication once per month during heartworm season. The amount depends on their weight. Also, you should never give your pet these meds if you suspect that he is already infected with heartworm.


What is Ivermectin

The parasite control drug Ivermectin was developed in the 1970s and approved for veterinary use in the late 1980s. It is derived from a fungus and was initially used as a medication to help control intestinal and other internal animal parasites.

Since then, oral ivermectin (also known by the brand name Stromectol) has proven to be the most effective substance for the treatment of animal scabies which causes mange. It is also commonly used in the treatment as well as a means of prevention of heartworm disease in dogs, cats and other domestic animals such as guinea pigs, horses, and cattle.

Ivermectin is a veterinary prescription medication available as a liquid for dispensation to larger animals and as a more economical choice for breeders who need large amounts.

The drug effectively kills any new heartworm larvae that may be present or have been introduced into the bloodstream since the last medication, thereby preventing them to mature and travel to the heart and lungs.

Ivermectin acts as a preventative by killing off the immature larvae but it does not kill adult heartworms. Because mosquitoes are found in nearly every corner of the world, it is important to put your dog or cat on a monthly schedule to prevent the development of adult heartworms and possible onset of this killer disease.

For household pets, palatable commercially available heartworm preventative medications that include ivermectin are Heartgard®, Iverhart®, Tri-Heart® and others.

These products are packaged in tablet or chewable format to be administered once a month. Formulas are available for both dogs and cats. Dosage is determined by the animal’s body weight. Most veterinarians recommend starting your puppy or kitten on heartworm preventatives by the time they are 8 weeks old.

Benefits of using Ivermectin For Dogs

Prevention is the best medicine when it comes to heartworm because it can be fatal. Having your veterinarian tell you which heartworm medicine for dogs is best will keep your dog healthy, active, and heartworm-free. There are several kinds of medications on the market today for this condition and you need to become familiar with them before you purchase one.

There are many strong active ingredients in heartworm medicine. The way they work is to paralyze the nervous system of the parasites to prevent them from moving further around your dog’s bloodstream. Other common dog diseases, such as tapeworm, hookworm, roundworm, and whipworm are also cured using ivermectin for dogs.

Correct Dosage Of Ivermectin For Dogs

One common problem dog owners have is that they tend to overuse the heartworm medicine. The medicine is very powerful and you need to be careful in giving the correct dosage to your dog. Over medicating will lead to your dog’s grogginess, loss of appetite, and even blindness. You can have your veterinarian give the dog the dosage if you are not sure how. Or you can read and follow the instructions on the medicine box carefully.

When you purchase and decide to give the heartworm medicine to your dog yourself, you need to test the pet for allergies and if there are toxic reactions to the particular medicine you have selected. Research your medicines side effects and read the caution section on the box carefully. Once the heartworm medicine is administered, watch your dog for any side effects, hypersensitivity and bad reactions.

Using Ivermectin For Dogs

Most of the ivermectin for dogs on the market today is highly effective. Make sure you research the generic brands. These days, they are as good as the more expensive popular ones. Go to the trusted websites online and get more information before you buy. Your vet can give you a more comprehensive list of medicines that you can use for your dog’s health. Always select the best care for your pet, because it deserves to be as healthy and as happy as any human being

Ivermectin Dosage

The exact dosage depends on the weight of the animal. Dosage instructions are on the pamphlet that comes with your Ivermectin bottle. When manufactured for swine and cattle and purchased from a livestock agricultural store or online without a vets script; exact same stuff just immensely cheaper than the Heartgard name brand. You may find it in multiple potencies—here on the farm, we use 1% solution. Ivermectin has been retailed “off-label” for our canine friends; there are warnings that it is unsafe in some Shelties, Collies, and mixed-breeds of these when given in a dosage ample enough for the treatment of worms (intestinal). For the breeds listed above, you may want to consider a lower dose, or alternatively use fenbendazole, a drug that is also reasonably successful against Giardia.

For both ticks and worms, I purchase Ivermectin (Ivomec™ is one of many brand name)—it’s labeled “for swine and cattle”— at livestock agricultural stores in 50-ml containers of 1% injectable Ivermectin (this is the active ingredient in the brand name Heartgard™). It takes care of various worms in the canine species. A single bottle will perhaps last nearly all of a small dog’s life, but even with larger dog breeds, you will still be paying a fraction compared to those who use vet prescribed Heartgard! I keep mine in the refrigerator, although there doesn’t seem to be a shelf-life difficulty at room temperature.

The Heartgard brand dosage to prevent heartworm, as I once jotted down in my farm journal, from their old pamphlet, is 6 micrograms per kilogram of body weight. Purchasing the high-priced pills from the veterinarian is too costly for the majority of people, and you get the EXACT same results by shopping where farmers like myself shop. The insert in some containers of 1% ivermectin suggests one milliliter (1 ml = approx. 1 cc) per 110 pounds of cow and 1 ml per 75 pounds of pig. Medically and anatomically speaking, dogs are more related to pigs than to cows, and the pig dosage is a good starting point for nearly all breeds.

I use that level for the first dose when I to bring in a new dog to my kennel, to make sure I got rid of any hookworms and roundworms they may have brought with them. But then, I decrease the roundworm dosage to a regular monthly heartworm-preventative maintenance dose.

The pamphlet that comes with Ivermectin explains that “wide margin of safety [in mammals] is attributable to the fact that… [the active ingredients, lactones]… do not readily cross the blood-brain barrier.”  In other words, the chemical agent acts so much more on the brainless parasite than on your smart, “brainy” dog. In swine and cattle, the insert says, ivermectin is effective against gastro-intestinal lice, worms and mites.

I dose orally, not by injection, even though the bottle says “injectable” form from my local livestock agricultural store. You should realize that less of almost any drug gets into the circulatory system if ingested, than if injected. Keeping that in mind, the manufacturers’ suggested levels (designed for hypodermic injection) are usually a good bit below what they probably would recommend for oral administration. Leave the needle and syringe stuck in the bottle’s rubber stopper when not in use. Turn the bottle upside-down, draw the desired amount into the syringe, pull out the syringe while leaving the needle in the stopper (you’ll re-connect these after dosing the dog). Squirt the liquid into the dog’s mouth. Can’t be any simpler than that!


Do not give Ivermectin to Collies, Australian Shepherds or other sheepdogs. These breeds are genetically predisposed to side effects from certain drugs, including ivermectin.

You can purchase Ivermectin here.


For more information on heartworms and preventing them, contact your veterinary clinic.

See also: