Vet Buzz from Erin Troy, DVM, CCRP,
Muller Veterinary Hospital
, Walnut Creek, CA
We are all struggling right now with the right choice of heartworm prevention for each dog. There are supply issues with established products as well new products that we may be unfamiliar with and it makes it all very confusing.
Let’s start first with the basics that can clear up some misunderstandings. According to Dr. Mark Kittleson DVM PhD DACVIM (Cardiology) at UC Davis all heartworm preventatives are from the macrocyclic lactone family. This family is further divided into avermectins, which includes ivermectin as in Heartgard Plus, and milbemycin which is in Interceptor and Sentinel and Trifexis.
Even more important to know is that the amount of ivermectin in Heartgard Plus is not now nor ever has been toxic to ANY breed of dog regardless of MDR1 status. The dose of ivermectin in Heartgard Plus, 6-12mcg/kg, is far too low to cause a toxicity. Ivermectin toxicity occurs at a dose of 50mcg/kg in the MDR1 mutant dogs and at a dose of > 100mcg/kg in non- mutant dogs. Keeping this in mind Heartgard Plus is a safe option for heartworm prevention in any dog. There are occasions where ivermectin can be prescribed at much higher doses than is present in Heartgard Pluse and this would not be done in a dog suspected or confirmed sensitive to ivermectin . If you are still not convinced that you want to put your dog on an ivermectin containing product then Trifexis would be another option that is just as safe for monthly protection.
I hope that this helps put your mind at ease and makes it easier for you to make the right choice for your dog.