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This is a Clinical condition.

Multiple Drug Sensitivity

What is MDR1?

Sensitivity to certain classes of drugs, notably the parasiticide ivermectin, as well as certain gastroprotectant and anti-cancer medications, occurs in dogs with mutations in the ABCB1 gene. Symptoms can range from vomiting and diarrhea to lethargy, seizures, or coma. The ABCB1 mutation is particularly common in herding breeds including Australian Shepherds, Collies, and Border Collies, though many other dog breeds are affected. Please note that the dosage of problem drugs in commercially available heartworm, flea, and tick preventatives should not cause symptoms in MDR1 dogs.

What are the signs & symptoms that develop in affected dogs?

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.

When do signs and symptoms develop?

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.

How do vets diagnose this condition?

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.

How is this condition treated?

MDR1 is perfectly avoidable simply by avoiding the problem drugs, or problem dosages.