Multi-drug resistance (MDR1) testing for dogs explained

Multi-drug resistance (MDR1), sometimes called multi-drug sensitivity, causes hypersensitivity in certain dogs to a broad range of medications including commonly used antibiotics and painkillers. Dogs with this condition have a genetic defect affecting proteins responsible for transporting drugs out of the brain, leading to toxic drug buildup that can cause seizures, neurological symptoms, blindness, or even death.

This hereditary condition cannot be contracted or developed outside genetic inheritance. It is important for breeders and owners of at-risk breeds to consider pre-breeding MDR1 testing. This helps inform breeding choices and protects affected dogs from harmful medications.

In this guide, we’ll explore MDR1 in detail: which breeds are most commonly affected, how the genetics work, methods to get your dog tested, and how testing protects your pet.

Understanding Multi-drug Resistance (MDR1) in Dogs

MDR1 most often occurs in certain herding and working dog breeds. It causes sensitivity to several classes of drugs including painkillers, sedatives, antibiotics, and chemotherapy agents.

If a sensitive dog receives any problematic drug, their brain’s ability to eliminate it is impaired, allowing harmful substances to accumulate to dangerous levels. This can lead to devastating signs such as seizures, nerve disorders, blindness, and can be fatal in severe cases.

Which Dogs Are At Risk of MDR1?

MDR1 primarily affects several herding breeds including the Border collie puppies, Old English sheepdog puppies, rough collie puppies, smooth collie puppies, and German shepherd puppies. Other breeds and mixed-breed dogs with ancestry from these groups may also carry the mutation.

You can check if your dog’s breed has hereditary health risks, including MDR1, using The Kennel Club’s DNA Screening Schemes by Breed search tool. This helps responsible owners and breeders stay informed.

Remember, only dogs who inherit the defective gene are susceptible — MDR1 is genetic and cannot transfer between dogs otherwise. Testing allows you and your vet to avoid medications that could harm your dog.

Genetics Behind MDR1: How Heredity Works

MDR1 is an autosomal recessive condition. This means that a dog must inherit two copies of the faulty gene (one from each parent) to be affected and sensitive.

If both parents carry the gene mutation, their puppies may inherit the condition. If one parent is affected and the other is clear, puppies will be carriers but usually not affected. If neither parent carries the mutation, their litter won’t have MDR1.

Understanding this inheritance helps breeders avoid mating two carriers, reducing the risk of affected puppies and promoting healthier breed lines.

How to Get Your Dog Tested for MDR1

If you own or plan to breed a dog of an affected breed, testing is vital. It ensures that only healthy dogs are bred and that your dog avoids dangerous medications.

If not breeding, knowing your dog’s MDR1 status helps your vet make safe medication choices. You can request a test through your vet, who will collect a cheek swab (buccal sample) for laboratory analysis.

Test results generally return within a week and determine if your dog is clear, a carrier, or affected. Results can be registered with The Kennel Club to contribute to breed health studies and encourage responsible breeding.

For a list of approved laboratories offering MDR1 testing, visit The Kennel Club’s worldwide DNA tests page. Tests typically cost around £50-£70, depending on the lab.

Why MDR1 Testing Matters for Your Dog’s Health

MDR1 testing provides critical information that supports responsible breeding and safeguards your dog’s health by preventing exposure to harmful drugs.

Many common veterinary medicines can cause severe reactions in MDR1-affected dogs, so knowing your dog’s status allows you and your vet to tailor treatments safely and avoid preventable tragedies.

Ultimately, testing empowers you to protect your dog and contribute to improving breed health standards by reducing the prevalence of this dangerous hereditary condition.