Multidrug Resistance 1

Body function:

Immune & Autoimmune

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Multidrug Resistance 1, or MDR1, is an inherited disorder affecting herding breeds like Collies and Australian Shepherds. A mutation in the ABCB1 gene causes abnormal production of p-glycoprotein, a compound that protects the brain from drugs and chemicals in a dog’s bloodstream. Dogs with this mutation are more sensitive to the negative side effects of medications like antiparasitics, antidiarrheals, and anticancer drugs.

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List of affected breeds:

Genetic research has linked this gene and condition in the following breeds:

Australian Shepherd, Border Collie, Collie, German Shepherd, Whippet, Mixed Breed, Old English Sheepdog, Shetland Sheepdog, White Swiss Shepherd Dog, Silken Windhound, Miniature American Shepherd, Huntaway

A brown dog with floppy ears is looking up at the camera with its mouth open and tongue out. The dog is standing in a field of tall grass.

What does this mean for a dog with this trait?

There is no cure for dogs with MDR1. Dogs experiencing symptoms of MDR1 should be seen by a vet immediately. Veterinarians may decrease dosages or switch to other drugs to mitigate symptoms.

Symptoms

Dogs with MDR1 experience symptoms of neurotoxicity when exposed to these drugs. This may include lethargy, ataxia, seizures, blindness, and other life-threatening symptoms.

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