Risks of Ivermectin CISC Newsletter 2006

SPECIAL HEALTH REPORT: Risks of Ivermectin
By Robin Smith

Oliver [an Icelandic mix] kept having re-occurring bouts of Giardia. They decided to try something outside of the normal range of treatment, which was giving him invermectin. Within a few days he fell suddenly very ill. He had diarrhea, then he stopped eating (which for him was unheard of); by the next morning he was listless and still not eating. By that evening he was refusing water. When I called him to come up stairs with me he didn't move and when I went to tug his collar gently he growled at me. Then he started throwing up. I knew that we needed to take him to the vet immediately, because at the minimum he was at risk of dehydration.

As we were getting him ready to go to the emergency room, he started having blood in his vomit. We took him to the ER - they thought he had swallowed something that was lodged in his stomach or gut. I said that was highly unlikely because he doesn't swallow things. They also asked if he could have gotten into rat poison or anything else. I don't keep anything like that in my house and we don't leave him out unattended in the yard.


They put him on an IV drip, gave him medication to keep him from vomiting and kept him over night. When we came to get him the following morning to take him to his regular vet he was still unable to hold down any food or water. They told me the tests that they had run indicated that his liver was in very bad shape. In essence he was experiencing liver failure. They ran all sorts of diagnostics to try to find a viral cause. They couldn't.


Then one vet said "it could have been the medicine we gave him this last time for his giardia. Some dogs have been known to react badly to that medication". Oliver stayed in the hospital for 3 days before he could hold down food or water. The vet stated that he probably would have died had he not been hospitalized. I know he was in pain and suffering greatly during this time.
The vet never warned us that the medicine they were giving him could cause him trouble. It is down on his paperwork that he is a border collie mix.

While we now know that he is most likely an Icelandic mix, the vet still should have known that invermectin and collies don't mix well. The vet also never apologized or gave us a reduction on our $1,200 vet bill.


All I can say, is that I am glad that I know enough about dogs to know when to take an animal to the ER. Otherwise Oliver would have died from liver failure at 2 years of age.
It is my understanding that this medication is a regularly used medication in skin conditions like mange. It is also regularly used as a heartworm medication. Since my vet didn't raise the issue with me, I now know to always ask what the potential side effects and risks are for any medication they are prescribing.


(Editor’s note: Icelandic Sheepdogs, like Collies and related herding breeds, may have a serious reaction to the drug ivermectin. About 75% dogs of these breeds or mixes have a specific gene mutation, which causes the ivermectin to build up to toxic levels in the brain.

Ivermectin is used in low doses in Heartgard-30 Plus for treating heartworm and other worms, and in higher doses it is used to treat sarcoptic and demodectic mange, ear mites and Cheyletielliosis (Dogs In Canada, March 2006).

If your dog needs to be treated for any of these conditions and ivermectin is suggested, inform your vet that, because of his breed type, he is at risk of a bad reaction and consider either alternative treatment or an ivermectin sensitivity test.