What is the MDR1 Gene Mutation?

Dogs can be born with genetic mutations that impact their health. One such mutation is the MDR1 gene mutation. The MDR1 (multi-drug resistance-1) gene is responsible for the production of P-glycoprotein, which is normally responsible for transporting certain drugs out of the brain. The MDR1 gene mutation is generally found in many herding breeds, some sighthound breeds and many mixed-breed dogs.

Dogs that have a mutation in the MDR1 gene, which inhibits their ability to remove certain drugs from the brain and can lead up to a buildup of toxins, may have severe adverse reactions to some common drugs, including seizures, tremors, disorientation, blindness, lack of muscle control or even death.

Which breeds are affected?

  • Australian Shepherd  
  • Border Collie
  • Collie
  • English Shepherd
  • German Shepherd
  • Long-Haired Whippet
  • McNab
  • Miniature Australian Shepherd
  • Mixed Breed  
  • Old English Sheepdog
  • Shetland Sheepdog
  • Silken Windhound

Dogs may be sensitive to:

  • Antibiotics such as erythromycin and rifampin
  • Anti-cancer drugs such as doxorubicin, vinblastine and vincristine
  • Anti-diarrheal drugs such as loperamide (Imodium®)
  • Certain parasite-control products such as ivermectin (in high doses), milbemycin, moxidectin and selamectin
  • Pain medications such as butorphanol
  • Tranquilizers/sedatives such as acepromazine

It’s important to note that when given at the recommended dose, the medications used in monthly heartworm preventives are at levels safe enough even for dogs with the MDR1 mutation.

Your dog should be tested for the gene before it receives any of the drugs listed above. The results can help you and your veterinarian when planning your pet’s future healthcare. A MDR1 test, which is part of Banfield’s Canine Genetic Analysis™ Test, will screen for this genetic mutation. You can talk with your local Banfield veterinarian about purchasing this test, or adding it to your Optimum Wellness Plan®.