Multiple Drug Sensitivity
Sensitivity to certain classes of drugs, notably the parasiticide ivermectin, as well as certain gastroprotectant and anti-cancer medications, occurs in dogs with a mutation in the ABCB1 gene.
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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. -
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
- Review the MDR1 Problem Drug List as described by Washington State University and notify your veterinarian to flag this in your dog’s file!
- Farm dogs with MDR1 may also benefit if they are either kept away from herds where ivermectin is used as a routine antiparasitic, or if another form of antiparasitic is used in areas that they are working.
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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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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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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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