Ivermectin is an antiparasitic drug for the control of certain internal and external parasites. It rids our animals’ bodies of these parasites by paralysing them so that they can be excreted or fall off. Ivermectin is used routinely in cattle and horses but is used off-label in dogs.
Ivermectin toxicity can occur whether it is given by injection, orally or applied topically in high enough doses. If it is present in high enough amounts in the dog’s body, it will cross the blood-brain barrier and cause neurological symptoms.
Symptoms include vomiting, seizures, tremors, blindness, incoordination, hypersalivation, dilated pupils, coma and death in severe cases.
There is no effective antidote and treatment consists of decontamination, as well as symptomatic and supportive care. In cases of oral ingestion (less than 4 hours after ingestion), your vet can induce vomiting to prevent further absorption. Activated charcoal is given orally as ivermectin recirculates in the gastrointestinal tract. If toxicosis is due to topical exposure, you should wash your dog thoroughly with a dishwashing detergent and water to remove the substance from its coat. The mainstay of treatment involves intravenous fluid therapy. In severe cases the animal might succumb to the toxicity or euthanasia can be considered.
Young dogs/puppies are more susceptible to toxicity due to their immature blood brain barrier. Some dogs have an ABCB1 gene mutation that causes increased permeability of the blood-brain barrier. These dogs are a lot more susceptible to Ivermectin toxicity. Examples of dogs with an ABCB1 mutation includes Border collies, rough and smooth coated collies, Australian shepherd dogs or any similar mixed breed dogs. All these dogs usually have white coloured paws/distal extremities. In the case of Ivermectin it is best to remember – Don’t treat white feet!
Ivermectin may be used to treat your dog for mange. As mentioned before, treatment is off label and should be done with your consent and after your vet has warned you about any potential side effects.
Of course we can’t talk about Ivermectin without thinking about the craze this drug brought about during COVID times. Please follow the link below to learn more about the drug and if there is any merit to using animal Ivermectin formulations in humans.