It is well known that Collies and related herding breeds can have adverse reactions to certain medications, even when given at the normal dosage. It was previously unknown why some individual dogs were sensitive and others were not.

Recent advances in molecular biology at the Washington State University's College of Veterinary Medicine have led to the discovery of this cause of multi-drug sensitivity in affected dogs. The problem is due to a genetic mutation in the multi-drug resistance gene (mdr1). Dogs with the mutant gene can not pump certain drugs out of the brain as a normal dog would, which may result in abnormal neurologic signs, illness, and even death. 

A test has recently been developed at Washington State University to screen for the presence of this mutant gene, enabling  veterinarians to determine if a dog can receive certain medications safely and without worry of serious side effects.

Affected Breeds

Approximately 3 of every 4 Collies in the United States have the mutant gene.

The MDR1 mutation has also been found in;

Shelties
Australian Shepherds
Old English Sheepdogs
German Shepherds
Long-haired Whippets
Silken Windhounds
and a variety of mixed breed dogs.

The only way to know if an individual dog has the mutant mdr1 gene is to have the dog tested. As more dogs are tested, more breeds will probably be added to the list of affected breeds.

Governor Animal Clinic is now offering this test for the mutant mdr1 gene with results generally returned within two weeks.  The test is simple, painless and involves getting a swab of your dog's cheek/mouth cells.  If you own one of the breeds prone to have the mutant mdr1 gent, we encourage you to test your dog soon, so that we can know which medications are to be avoided in the future.  This important information will also help you if you take your dog to an emergency clinic or a specialty hospital.

There are many different types of drugs that have been reported to cause problems in these dogs, ranging from over-the-counter antidiarrheal agents like Imodium, to tranquilizers, immunosuppressants, cardiac drugs, antiparasitic and chemotherapy agents.

Examples of some of the drugs are

Ivermectin (antiparasitic agent)
Loperamide (Imodium®; over-the-counter antidiarrheal agent)
Doxorubicin (anticancer agent)
Vincristine (anticancer agent)
Vinblastine (anticancer agent)
Cyclosporin (immunosuppressive agent)
Digoxin (heart drug)
Acepromazine (tranquilizer)
Butorphanol (pain control)

Potential Problem Drugs

The following drugs may potentially cause problems when given to dogs that have the mutation. Biochemical studies have shown that this gene has the potential to act on over 50 different drugs.

Ondansetron
Domperidone
Paclitaxel
Mitoxantrone
Etoposide
Rifampicin
Quinidine
Morphine

It is likely this list will grow to include more drugs as research progresses.

Please call our office today @ 858-453-6312 to set up an appointment for testing.