Most of us who have horses have Ivermectin in our barns. It’s probably the most common de-wormer out there. But did you know that Ivermectin can be toxic to dogs?

I never knew this, but it’s something we should all be aware of, especially because many people use Ivermectin to treat heart worm and mange in dogs and might not think twice if Rover laps up some of it next time you worm your horses.

Most of the time toxic reactions occur when a dog ingests 10-20 times the recommended canine dose. However, some breeds are highly sensitive to Ivermectin and a fatal dose can be quite small. The drug is particularly toxic to herding breeds such as Collies, Old English Sheepdogs, Shetland Sheepdogs, Australian Shepherds, Border Collies, and Shelties. Also affected are Jack Russell Terriers. There’s even a rhyme for veterinarians about Ivermectin: “White feet, don’t treat.”

Even if you’re careful with medications there are many ways that a dog can ingest Ivermectin such as picking up a used tube out of the garbage or licking up medication that a horse has spit out onto the floor. I have a dog that would certainly go after anything that he thinks looks edible and in retrospect I think I’m just lucky that he hasn’t eaten any becuase it just hasn’t been on my radar screen.

Signs of Ivermectin overdose.

Reaction to Ivermectin generally occurs within 4-8 hours of exposure and includes:

• Dilated pupils
• Depression
• Excessive drooling
• Vomiting
• Tremors
• Disorientation
• Weakness
• Recumbency (inability to rise)
• Weakness
• Blindness
• Nonresponsiveness
• Slow heart rate
• Lack of appetite
• Stupor
• Slow respiratory rate
• Coma or death
• Seizure

What should you do?

If you suspect Ivermectin poisoning the first thing you should do is call your vet.

If it’s only been a few hours you can also induce vomiting (which can be done with hydrogen peroxide) or feeding activated charcoal. Because Ivermectin persists in the body for several days and keeps returning to the gut before being excreted in feces, giving multiple doses of activated charcoal can speed recovery by actually decreasing the dose of drug that the dog receives.

There is no way to reverse Ivermectin toxicity so the only treatment is supportive care which may be better provided by your veterinarian.

Many dogs do recover from overdoses of Ivermectin but sadly, others do not. Keeping your dogs away from Ivermectin is the only sure strategy of preventing an overdose.