MDR1 Drug Sensitivity
This genetic variant makes some dogs sensitive to certain medications, including some dewormers, anti-diarrheals, pain medications, and chemotherapies. Side effects may be stronger than expected, so it’s important your vet knows before prescribing.
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Signs and symptoms
MDR1 often presents in young adulthood, only because this is most commonly when a dog is first exposed to a problem drug like high dose ivermectin or acepromazine.
Symptoms arise after a dog has received an MDR1 problem drug or dosage, and can range from vomiting and diarrhea to lethargy, seizures, or coma.Uncover health risks with Embark
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Diagnosis
This is usually a retroactive diagnosis after a dog has an adverse reaction to a problem drug--however, genetic testing could help you avoid a first reaction altogether.
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Treatment
MDR1 is perfectly avoidable simply by avoiding the problem drugs, or problem dosages.
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What to do if your dog is at risk
Actions
- Talk to your vet about your dog’s MDR1 result and share Washington State University’s list of potential problem drugs.
- Monitor your dog in areas with horses or livestock, as ivermectin and similar problem drugs are often stored or used in these locations.
- Prevent your dog from eating livestock feces, which can contain harmful levels of certain problem drugs.
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Genetic Information
The Multidrug Resistance, ABCB1 mutation, is particularly common in herding breeds including Australian Shepherds, Collies, and Border Collies, though many other dog breeds are affected. The veterinary adage, "White feet don't treat!" draws from the fact that many high risk breeds often have white markings on their feet; however, we know now that MDR1 is common in many dog breeds and mixes, many of whom do NOT have white feet!
Gene names:
ABCB1 ‐ chr
Inheritance type:
codominant
Citations:
Mealey et al 2001 , Han et al 2010 , Neff et al 2004 , Barbet et al 2009 , Gramer et al 2011
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Breeds affected
This health condition affects the following breeds
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Australian Cattle Dog
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Australian Shepherd
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Border Collie
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Chinook
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Collie
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Collie (Scottish-Type)
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Czechoslovakian Vlcak
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Danish-Swedish Farmdog
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English Shepherd
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German Shepherd Dog
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Australian Kelpie
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Koolie
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Windsprite
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McNab
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Miniature/MAS-type Australian Shepherd
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Old English Sheepdog
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Saarloos Wolfdog
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Shetland Sheepdog
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Shiloh Shepherd
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Silken Windhound
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Whippet
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White Shepherd
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