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. If you would like to speak to a vet online you can book an online consultation and discuss your pet's condition via video chat at PawSquad.
Disclaimer
Vets Now assumes no liability for the content of this page. This advice is not a substitute for a proper consultation with a vet and is only intended as a guide. Please contact your local veterinary practice for advice or treatment immediately if you are worried about your pet’s health, even if they are closed, they will always have an out-of-hours service available.

