What is ivermectin toxicity in dogs?

Ivermectin is a medication used to treat parasite infections in animals. It works by interfering with parasites’ nervous systems to paralyse and kill them.

While ivermectin can be prescribed for dogs, toxicity can occur when dogs ingest more ivermectin than they should.

Is ivermectin dangerous for dogs?

When administered appropriately in a veterinary setting, ivermectin can be useful for treating many parasitic infections that affect dogs.

That said, if dogs are exposed to higher levels of ivermectin, for example, if they eat the poo of a horse that has recently been treated or eat a bottle of medication – ivermectin can be toxic.

Ivermectin is readily absorbed through the skin (it is used as a pour-on or spot-on for many species) so pets can also be exposed without ingesting the drug.

It is also important to note that many breeds, mainly herding breeds descended from or related to collies, including Australian Shepherds, Shetland Sheepdogs, rough/smooth/border collies, and many more, carry a defective MDR1 gene.

These breeds cannot effectively metabolise ivermectin, which can be toxic and even lethal for them at low doses.

Your veterinarian will know these breeds’ susceptibilities and consider that when planning treatment for worms or parasites.

If you have a dog with collie ancestry, you should be extra careful about the possibility of exposure to ivermectin in the environment.

What are the signs of ivermectin toxicity in dogs?

The symptoms of ivermectin toxicity in dogs can vary depending on the dog’s size, the amount of ivermectin ingested, and the individual dog’s sensitivity to the drug.

Common signs of ivermectin toxicity include:

  • Vomiting
  • Diarrhoea
  • Drooling
  • Lethargy
  • Tremors or seizures
  • Ataxia (loss of coordination)
  • Pupil dilation
  • Blindness
  • Difficulty breathing
  • Coma

How is ivermectin toxicity treated?

If you suspect your dog has ingested excessive ivermectin, seek immediate veterinary attention.

Early identification and swift treatment are vital to a positive outcome.

Treatment for ivermectin toxicity may involve:

  • Decontamination of the skin
  • Medications to reduce absorption
  • Providing supportive care such as intravenous fluids
  • Medications to control symptoms

If you have concerns about whether your dog has received high doses of ivermectin or the potential side effects of coming into contact with it, contact your local vet. Or, if out of hours, contact your local Vets Now emergency clinic or speak to one of our vets directly through our Video Vets Now telehealth service.