MDR1 testing

What you need to know about MDR1 testing

Some dogs – including as many as 75% of specific herding breeds – and around 4% of all cats have a dangerous mutation in what is known as the MDR1 (multidrug resistance 1) gene, which, if undetected, can lead to severe adverse reactions to many common medications.

The only way to determine if your pet has the mutation is through MDR1 testing.

What is an MDR1 test?

The first MDR1 test was developed by a team of researchers at Washington State University led by veterinary pharmacologist Dr. Katrina Mealey. An MDR1 test will determine if a dog or cat’s DNA contains a specific mutation in the MDR1 gene that makes the animal susceptible to adverse drug reactions.

Why purchase an MDR1 test from WSU?

When you order an MDR1 test from WSU, you can be confident you will receive fast and accurate results you can trust. When an animal is genotyped through WSU, clients also gain access to PrIMe’s online portal, where questions regarding medications can be submitted directly to staff and Dr. Mealey. Our team can work with you and your veterinarian to determine the best course of action should your pet need to be treated with a medication known to cause adverse reactions in animals with the mutation.

Dr. Mealey discovered the MDR1 mutation in both cats and dogs and is recognized worldwide as the leading expert in identifying problem medications. She and her team of researchers at WSU were the first to develop a genetic test to identify animals with the mutation and to make it commercially available for pet owners and veterinarians.

“This can be a life-or-death condition – if a dog or cat is incorrectly genotyped and treated with the one of the problem drugs, it can kill the animal,” Dr. Mealey said. “Pet owners should read the fine print before having their pet tested with just any company. Many of them state that their results are not intended to be used as a basis to establish a diagnosis or treatment.”

How do you test a dog or cat for MDR1?

Testing a dog or cat for MDR1 is simple and quick, requiring only a DNA sample. DNA can be obtained from your pet’s cheek cells using a swab or from your pet’s blood. WSU offers tests using either type of sample because cheek swabs are an easy way for dog or cat owners to collect DNA samples in their own homes, while blood samples are often preferred by veterinary clinics and hospitals.

Once your pet’s DNA sample is returned to WSU, results will usually be available within about a week. WSU is the only testing service that provides qualified clinical pharmacology counseling. MDR1 tests for dogs and cats can be ordered here.

What does MDR1 positive mean?

All animals have the MDR1 gene – also known as the ABCB1 gene – and are thus “positive.” The gene encodes P-glycoprotein, which plays an important role in limiting drug distribution to the brain and in enhancing the excretion of many drugs. Dogs and cats with a mutation in the gene may have severe, potentially fatal, adverse reactions to some common medications. To avoid confusion, terms that reflect an animal’s actual MDR1 genotype (i.e., MDR1 mutant/normal) should be used instead of “MDR1 positive.”