Ivermectin for Dogs: Safety and Side Effects

Brown and long-haired dachshund dog sitting on grass under packet of ivermectin

Ivermectin is a drug that is routinely used to treat a range of ailments in dogs and cats. It's used to treat parasite infections of all kinds. Ivermectin is widely used to treat both internal and exterior parasites. It's also found in numerous over-the-counter heartworm preventatives, including as Heartgard Plus and others.

Safety of Ivermectin in Dogs

In many circumstances, the dosage of ivermectin is directly proportional to its safety. Increased doses, like many medicines, are associated with a higher risk of problems and serious adverse effects. Ivermectin comes in a variety of dose forms, depending on the intended application. The doses used to prevent heartworm infections are usually rather modest, with little chance of negative effects.

Higher doses are more likely to cause side effects, such as those used to treat demodectic mange, sarcoptic mange, ear mites, and other parasite illnesses. Ivermectin, on the other hand, is regarded a generally safe drug for most dogs when taken properly.

How Ivermectin Works

Ivermectin's main function is to destroy parasites. This is accomplished by inflicting neurological harm on the parasite. The parasite is paralyzed and dies as a result of this harm.


Certain dog breeds are genetically susceptible to the medicine. The ivermectin is able to pass through the blood-brain barrier because of their genetic mutation. It subsequently makes its way into the dog's central nervous system, where it can be deadly. Check with your doctor to ensure that your dog's breed is safe to use ivermectin before giving it to him.

Side Effects of Ivermectin in Dogs

The likelihood of ivermectin-related adverse effects in dogs is dependent on the dosage, the individual dog's sensitivity, and the presence of heartworm microfilaria (a larval form of the heartworm.)

Ivermectin is reasonably safe when taken at a low dose for heartworm prevention in a dog that is heartworm-free. The danger of negative effects increases when the dose is increased, which might be used to treat other parasite illnesses. The following are examples of possible negative effects:

  • Vomiting
  • Dilated pupils
  • Muscle tremors
  • Blindness
  • Lack of coordination
  • Lethargy
  • Lack of appetite
  • Dehydration

When administered in a dog with heartworms, it can elicit a shock-like reaction, which is thought to be caused by dying microfilaria. Lethargy, a low body temperature, and vomiting are all possible symptoms of this response. Following the treatment of ivermectin, dogs who test positive for heartworms should be closely monitored for at least eight hours.

Ivermectin Sensitivity in Collies and Similar Breeds

In certain dogs, ivermectin use can lead to neurotoxicity. This is especially prevalent in dogs that have a genetic mutation known as the MDR1 gene mutation (multiple drug resistance). Collies, Australian shepherds, Shelties, Long-haired whippets, English sheepdogs, German shepherds, Silken Windhounds, Skye terriers, and other breeds with white feet have been found to carry this gene mutation. The slogan "white feet, do not treat" with ivermectin comes from the symptoms of neurotoxicity, which include lack of coordination, muscular spasms, convulsions, blindness, and death.

These dogs are typically safe when given ivermectin at heartworm preventive levels. However, dogs with the MDR1 gene mutation should not be given greater dosages of the medication. There is a test that may be done to see if this gene mutation is present. For further information, see your veterinarian.


Ivermectin poisoning is extremely dangerous and irreversible. If you suspect your pet is having an allergic reaction, contact your veterinarian straight away. To reduce medication absorption, they may advise causing vomiting or providing charcoal.

Ivermectin and Human Use

Ivermectin is used by doctors to treat a variety of human health conditions in addition to its usage in animal medicine. It can also be used to get rid of parasites in people. Head lice, scabies, river blindness, and other illnesses can all be treated with ivermectin. It can only be obtained with a prescription and is used topically or orally. Keep in mind that no medicine intended for animal usage should be administered to humans. There is currently no convincing evidence that ivermectin is effective or safe in people against SARS-CoV-2, the virus that causes COVID-19.

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.


"Ivermectin Toxicity In DogsTrumann Animal Clinic", "Antiparasitics For Integumentary DiseaseVeterinary Manual", "Ivermectin: Medlineplus Drug InformationMedline Plus" ;