What is MDR1?
Some dogs and cats have a mutation in the MDR1 (multidrug resistance 1) gene also known as the ABCB1 gene, which plays an important role in limiting drug distribution to the brain and in enhancing the excretion of many drugs. Animals with the mutation may have severe adverse reactions – including tremors, disorientation, blindness, severe muscle weakness, and death – to some common medications.
What Dog Breeds are Affected?
The following list shows breeds and their approximate percentage of dogs impacted.
- Australian Shepherd – 50%
- Australian Shepherd, Mini – 50%
- Border Collie – <5%
- Chinook – 25%
- Collie – 70%
- English Shepherd – 15%
- German Shepherd – 10%
- Herding Breed Cross – 10%
- Long-Haired Whippet – 50%
- McNab – 30%
- Old English Sheepdog – 5%
- Shetland Sheepdog – 15%
- Silken Windhound – 30%
What Medications are Potentially Dangerous?
- Ivermectin (antiparasitic agent)
- Selamectin, milbemycin, and moxidectin (antiparasitic agent)
- Loperamide (Imodium TM: antidiarrheal agent)
- Acepromazine (tranquilzer and pre-anesthetic agent)
- Butorphanol (analgesic and pre-anesthetic agent)
- Chemotherapy Agents (Vincristine, Vinblastine, Doxorubicin, Paclitaxel)
- Cyclosporin (immunosuppressive agent)
- Digoxin (cardiac drug)
- Doxycycline (antibacterial drug)
- Morphine, buprenorphine, fentanyl (opioid analgesics or pain medications)
- Domperidone, Etoposide, Mitoxantrone, Ondansetron Rifampicin
What Can I Do for My Pet?
- Get your dog tested
- Order your test online from the following link Washington State University MDR1 Test
- Talk to your veterinarian
- Talk to your breeder