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Multidrug resistance 1 (MDR1) gene mutation in dogs

02 June 2024
9 mins read
Volume 15 · Issue 5
Figure 1. (a) Buccal swab sampling in a Shetland sheepdog for MDR1 gene mutation testing; (b) Kennel sign for high-risk dogs whose MDR1 genotype is unknown; (c) A hospitalised German shepherd with signage on its kennel confirming it has the MDR1 gene mutation.
Figure 1. (a) Buccal swab sampling in a Shetland sheepdog for MDR1 gene mutation testing; (b) Kennel sign for high-risk dogs whose MDR1 genotype is unknown; (c) A hospitalised German shepherd with signage on its kennel confirming it has the MDR1 gene mutation.


The multidrug resistance (MDR1) gene mutation in the domestic dog (Canis lupus familiaris) is an inherited condition most frequently observed in herding breeds. Dogs with the mutated gene are at risk of neurological toxicosis and life-threatening reactions if certain drugs are administered. Determining the MDR1 genotype of a dog via blood or buccal swab sampling will assist owners and veterinary professionals in understanding their risk of multidrug sensitivity. Some of the drugs known to be dangerous when administered to a dog with the mutation are used in everyday practice. To ensure patient safety, the student and registered veterinary nurse should have an understanding of this condition, particularly when dealing with the dog breeds at higher risk. This article aims to provide student and registered veterinary nurses with a comprehensive and logical analysis of the MDR1 gene mutation in dogs.

A dog with the MDR1 gene mutation, also known as multidrug sensitivity, is susceptible to neurological toxicosis and life-threatening reactions if certain drugs are administered (Mealey and Meurs, 2008). This condition is caused by the deletion of 4-base pairs of the MDR1 gene (Suriyaphol, 2011). P-glycoprotein (P-gp) is a product of this gene and a well-known multidrug transporter in the adenosine triphosphate binding cassette family (Ahmed Juvale et al, 2022). P-gp is found in various tissues throughout the body, including at the physiological barriers such as the blood-brain barrier where it acts as a drug-efflux pump (Geyer et al, 2009). Under normal conditions, the role of P-gp is protective. This includes the distribution and excretion of several drugs and restricting access of certain drugs and xenobiotics through the Blood-brain barrier (Gramer et al, 2011). P-gp function is impaired in dogs with a mutation of the MDR1 gene. This causes susceptibility to neurotoxicity if P-gp substrates and xenobiotics accumulate and cross the Blood-brain barrier, subsequently penetrating the central nervous system (Geyer et al, 2009).

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