milbemycin, heartworm medication, equine dewormer, Bimectin, ivermectin
Toxicity to pets
A class of drugs commonly used in veterinary medicine include ivermectin, milbemycin, and moxidectin; these are anthelmintics (these drugs kill parasites) and are commonly used as an active ingredient for monthly heartworm preventatives. Certain breeds of dogs (e.g., collies, Border collies, Australian shepherds, Old English sheepdogs, etc.) with a multidrug resistant (MDR) gene mutation are extremely sensitive to this class of drugs. Accidental poisoning can be seen in these sensitive breeds or when non-sensitive breeds get into a toxic amount. Toxic ingestions often occur when dogs accidentally ingest horse dewormer, which contains large amounts of ivermectin. Accidental poisoning has also been reported in dogs ingesting feces from horses that were recently dewormed. Clinical signs of poisoning include dilated pupils, tremors, drooling, seizures, coma, inability to breath, and death. Without aggressive treatment, ivermectin poisoning can be deadly.
The content of this page is not veterinary advice. A number of factors (amount of substance ingested, size of the animal, allergies, etc.) determine what is toxic to a particular pet. If you think your pet has eaten something potentially toxic, call Pet Poison Helpline or seek immediate veterinary treatment.