Hi stranger! Signing up for MypetMD is easy, free and puts the most relevant content at your fingertips.

Get Instant Access To

  • 24/7 alerts for pet-related recalls

  • Your own library of articles, blogs, and favorite pet names

  • Tools designed to keep your pets happy and healthy

or Connect with Facebook

By joining petMD, you agree to the Privacy Policy.

PetMD Seal

Parasite Drug (Ivermectin) Poisoning in Dogs


Ivermectin Toxicity in Dogs


This toxic reaction occurs especially in dogs that are genetically hypersensitive to ivermectin, an anti-parasite medication most commonly used for heartworm prevention, or to treat ear and hair mites, which can lead to mange. Ivermectin prevents or kills parasites by causing neurological damage to the parasite, resulting in paralysis and death for the parasite. But dogs genetically sensitive to the medication have an anomaly that allows the ivermectin to pass the dog's blood-brain barrier and into its central nervous system, which can be lethal for the animal.


While the sensitivity to this type of medication is not always guaranteed, the following breeds are most likely to be affected:



It is also seen in mixed-breed dogs, older dogs that have experienced a blow to the head, puppies, and dogs that have overdosed on similar types of drugs. Treating dogs that are susceptible to ivermectin toxicity with parasitic medication should be only be done under a veterinarian's supervision and with great caution.




Symptoms for the dog may be acute or mild. Acute signs will become apparent within 4 to 12 hours of the drug's administration. In mild cases, symptoms will occur between 48 to 96 hours after your dog has been treated. Such symptoms include: 


  • Lethargy
  • Depression
  • Drooling
  • Vomiting
  • Dilation of the pupil
  • Loss of appetite (anorexia)
  • Difficulty controlling voluntary movement
  • Disorientation
  • Tremors/Seizures
  • Inability to stand
  • Blindness
  • Slow heartbeat
  • Respiratory distress
  • Coma




Related Articles

Arsenic Poisoning in Dogs

Arsenic is a heavy metal mineral that is commonly included in chemical compounds for consumer products, such as herbicides (chemicals to kill...

Hypercalcemic Agent Poisoning in Dogs

Hypercalcemia is defined as abnormally elevated calcium levels in the blood. Of the various types of substances that are poisonous to dogs, there...