MDR1 test in the MyDogDNA panel

We have more exciting news to share! We are now taking one more step further in our efforts to bring you an even more complete and comprehensive panel for use in your breeding program.

We are now able to offer the Multi-Drug Resistance 1, (MDR1) mutation test, which will from now on be offered as part of the MyDogDNA® panel to all customers.

The mutation was originally identified in Collie-related breeds, but has been found in more than 15 different breeds to date. The MDR1 mutation is commonly found in a variety of mixed-breed dogs, and thus testing of all mixed breed dogs is recommended.

What is MDR1? :

Multi-Drug Resistance 1, (MDR1)

Multi-drug resistance 1 (MDR1) is a genetic mutation that alters a dog's ability to limit the absorption and distribution of many drugs. Dogs with the MDR1 mutation are slower to eliminate certain drugs from the body and can suffer side effects when exposed to these medications. This drug intolerance is sometimes also called "ivermectin sensitivity". However, the name is a misnomer as several other drugs pose a risk to MDR1 mutation positive dogs. This mutation is inherited in a dominant fashion though dogs with two copies of the mutation will exhibit more severe clinical signs.

Dogs that carry this mutation are asymptomatic until they are exposed to a medication that uses the pump that is rendered defective by the mutation in ABCB1 (MDR1) gene. Drugs known to use the P-glycoprotein pump are macrocyclic lactones (antiparasitic drugs), loperamide (antidiarrheal), erythromycin (antibiotic), acepromazine (tranquilizer), butorphanol (opioid), and certain drugs used in cancer treatment (vincristine, vinblastine, and doxorubicin). When these medications are administered, they accumulate in the brain which results in the adverse reactions. Typical symptoms include tremors, loss of balance, seizures, obtundation, excessive salivation, dilated pupils, and bradycardia. If untreated, the condition may lead to respiratory arrest, coma or death. However, all FDA (United States Food and Drug Administration) approved heartworm preventatives are safe to administer to MDR1 positive dogs. Because dogs with one copy of the mutation will have some P-glycoprotein function, the most severe cases tend to occur in dogs that are homozygous for the mutation. Dogs that are homozygous for the mutation will exhibit more severe clinical signs of adverse reactions because they lack any functional P-glycoprotein pumps, but please note that the condition can be very severe in dogs that have only one copy of the mutation as well.

Examples of dog breeds carrying the MDR1 mutation: Australian Cattle Dog, Australian Shepherd, Chinook, Collies, East-Siberian Laika, Miniature American Shepherd, Mixed breed dogs, Old English Sheepdog, Shetland Sheepdog, White Swiss Shepherd Dog, Windsprite (formerly Longhaired Whippet)