Natural pet care is often based on simple awareness and prevention.  There has been much talk about vaccine reactions in pets, but there is less awareness regarding the cause of adverse drug reactions.

Researchers at Washington State University College of Veterinary Medicine have determined there is a gene responsible for adverse reactions to over a dozen drugs often prescribed to dogs, called the multi-drug resistance (MDR1) gene.  Furthermore, there are certain herding breeds that have a higher chance of carrying the MDR1 gene.  Perhaps most alarming is many of the predisposed breeds are common in mixed breeds, such as the German Shepherd and Collie, so their mixed cousins may also carry the gene.

Breeds that Commonly Carry the MDR1 Gene

(Percentage of those Tested)

If you have any of the following breeds or mixes thereof, please ask your veterinarian to test for the MDR1 gene.

  1. Collie 70%
  2. Long-haired Whippet 65%
  3. Australian Shepherd 50%
  4. Miniature Australian Shepherd 50%
  5. Silken Windhound 30%
  6. McNab 30%
  7. English Shepherd 15%
  8. Shetland Sheepdog 15%
  9. German Shepherd 10%
  10. Herding Breed Cross 10%
  11. Mixed Breed 5%
  12. Old English Sheepdog 5%
  13. Border Collie <5%

If your dog is identified as a carrier, you can work with your vet to find alternative solutions. For example, you can substitute Calcium Montmorillonite Clay as a natural treatment of diarrhea instead of using Loperamide, one of the drugs identified as dangerous for dogs carrying the MDR1 gene.

Identified Drug Sensitivities

Dogs with the MDR1 gene have adverse drug reactions to drugs that are otherwise considered safe. The most serious reactions involve antiparasitic agents, the antidiarrheal agent Loperamide (Imodium), and several anticancer drugs.


We’ve designed an infographic to further create awareness of the MDR1 gene and to make it easier for you to keep on hand.  Please feel free to share it on social media, blogs, or other websites.

Dog Breeds Predisposed to Adverse Drug Reactions (Infographic)

Do you have any of the above mentioned breeds?  Have they experienced an unexpected drug reaction?  Please share your experience in the comments below.


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