Why is ivermectin contraindicated in some dog breeds? And what type of breeds are susceptible?
Certain breeds of dogs have an MDR1 mutation that means they do not pump Ivermectin back out of the CNS as they should and so the drug can act on chloride channels in the brain. This causes toxic symptoms which result in coma and death. Breeds affected include: collies, Australian shepherd dogs, shetland sheep dogs, etc.