Drugs for Dogs to Prevent Heartworm Disease


A potentially fatal parasite infection, heartworm disease damages dogs' hearts and lungs. Any dog exposed to mosquitoes has the danger of contracting heartworms, which are only carried by the mosquito. In the United States, heartworm illness in dogs is a very widespread condition. Due of this, regardless of environment, the American Heartworm Society advises year-round treatment with a Heartworm prophylactic for all dogs in the U.S.

It’s important to note that dogs living in areas that are warmer and more humid are at the highest risk since they tend to have more exposure to mosquitoes.

What Is Heartworm?

Dirofilaria immitis is a parasite that causes heartworm illness. When a mosquito bites a dog, the parasites' larvae enter the body through the blood arteries and make their way to the heart and lungs, where they can grow and cause fatal health issues.

What Are Heartworm Preventatives

Although they are marketed as "prevention," parasitic drugs known as heartworm preventatives actually kill the tiny heartworm larvae that are already present in the circulation. To prevent heartworm larvae from maturing into adults, these drugs are administered monthly. It is crucial to regularly provide these treatments since they are intended to destroy the young larvae. It is advised to take the missed dosage right away and to continue taking the prescription every 30 days if you are more than a month late. If you have missed more than one dosage, you should talk to your doctor before beginning again since a prolonged break from treatment might allow the heartworms to grow and make it unsafe to kill them off without a doctor's supervision.

Testing & Prevention

A veterinarian should do a heartworm test on all pets once a year. Contact your veterinarian if you miss more than one dose of heartworm prevention. Before resuming treatment, your dog may require another heartworm test. It's crucial to follow a veterinarian's exact instructions when administering heartworm prevention to a dog that has tested positive for the disease. Giving heartworm prophylaxis to a dog that is already heartworm positive may be dangerous in rare circumstances. In some circumstances, your veterinarian may advise close monitoring, extra drugs, and treatment precautions. Consult your veterinarian about the suggested next measures if you think your dog may be heartworm positive or if there has been a lengthy time since their last preventive.

Being a responsible dog owner means giving your dog heartworm protection. Additionally, preventing heartworms is safer and more affordable than administering heartworm medication to your dog. Heartworm therapy can be expensive and dangerous for the dog. The price of heartworm prevention varies annually based on the size of the dog and the chosen drug.

Talk to your veterinarian about the ideal heartworm prevention for your dog. There are several different medications that can be used on a regular basis to prevent heartworm infestation.

Types of Heartworm Preventatives


Some Brand Names: Heartgard Plus (by Boehringer Ingelheim); Iverhart Plus and Iverhart Max (by Virbac); Tri-Heart Plus (by Merck)

Heartworm treatments based on ivermectin are taken orally once a month. A broad-spectrum antiparasitic medication used on both people and animals is ivermectin. Ivermectin is a low-dose yet efficient heartworm larval killer used in monthly heartworm prevention. The "plus" denotes the inclusion of pyrantel pamoate, which kills including hookworms and roundworms, in the aforementioned brands of heartworm prevention. The "max" denotes the inclusion of praziquantel, a tapeworm-killing drug, as well.

Ivermectin seldom has negative side effects. If adverse effects do arise, they often have a neurologic origin (central nervous system depression, wobbly gait). Due to the ABCB1/MDR1 gene mutation, several dog breeds, including the Collie and Shetland Sheepdog, are known to be susceptible to ivermectin. However, even in sensitive breeds, ivermectin-based heartworm preventive drugs seldom result in adverse effects or responses at such low doses.

Milbemycin Oxime

Some Brand Names: Trifexis (by Elanco)​; Sentinel (by Merck)

Milbemycin-based Additionally, heartworm treatments are taken orally once a month. Milbemycin oxime is a broad-spectrum antiparasitic medication, similar to ivermectin. It is not used on people; only on animals. Roundworms, Hookworms, and Whipworms are also destroyed by Milbemycin. Both Trifexis and Sentinel include a different medication to stop flea infestations. Spinosad, the flea preventative in Trifexis, kills fleas. The lufenuron included in Sentinel stops flea eggs from developing but does not kill adult fleas.

Milbemycin typically has little negative effects when used as prescribed, while side effects with any medicine are always possible. Milbemycin overdose symptoms often include a neurological component (stupor, tremors, wobbly gait). At this time, no unique breed sensitivity has been documented.


One Brand Name: Revolution (by Pfizer)

One time per month, selamectin is topically administered. It is an antiparasitic medication solely prescribed for use in animals that eliminates fleas, guards against heartworm disease, and treats and manages hookworms, roundworms, and ear mites. The solution is administered using a little tube to the skin—not the hair—on the back, in the region between the shoulder blades. Effective application is dependent on proper execution.

Loss of appetite, excessive drooling, vomiting, diarrhea, muscular tremors, fever, fast breathing, or seizures are possible adverse effects of selamectin, however they are uncommon. Temporary hair stiffness or clumping, hair discolouration, hair loss, skin irritability, an oily area, or a powdery residue might occur where the product was applied.


Some brand Names: Advantage Multi (by Bayer); Proheart (by Zoetis)

Moxidectin is an antiparasitic medication that is only used on animals. It helps reduce hookworms, whipworms, and roundworms as well as certain skin mites that cause mange and prevents heartworm infections. There are two ways to deliver moxectin: Unlike Proheart 6 and Proheart 12, Advantage Multi is administered topically.

The monthly application of Advantage Multi is made to the skin, not the hair, on the back between the shoulder blades. For it to function properly, it must be applied appropriately. Advantage Multi includes imidacloprid, which kills fleas in addition to moxidectin. Lethargy, itching, and hyperactivity are possible Advantage Multi side effects, albeit they are uncommon. Temporary hair stiffness or clumping, hair discolouration, hair loss, skin irritation, or a powdery residue might occur where the product was applied.

Depending on the kind utilized, proheart is injected subcutaneously (under the skin) once every six to twelve months. The moxidectin is in a sustained release formulation, enabling it to persist for the time period specified on the label. Many owners find that this method of heartworm prevention is the best since it does away with the need to remember monthly medications. Mild to severe allergic responses, lethargy, convulsions, vomiting, diarrhea, weight loss, and fever are some potential adverse effects, albeit they are rare.


It might be difficult to choose the best heartworm preventive for your dog. It is crucial to discuss the best solutions with your veterinarian for both you and your dog. Whatever you choose, make sure your dog is on heartworm protection the entire year. It might be the difference between your dog's life and death.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.


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