Medications and Drugs to Avoid with Australian Shepherds

Here are the answers to the common questions about MDR1 in Australian Shepherds:

Common Questions About MDR1 in Australian Shepherds (with Answers)

1. What is MDR1 and why is it significant for Australian Shepherds?

   • What does MDR1 stand for? MDR1 stands for Multi-Drug Resistance 1. It refers to a gene (now officially called ABCB1) that is responsible for producing P-glycoprotein, a protein pump that plays a crucial role in protecting the brain and other sensitive organs from potentially harmful drugs and toxins.

   • Why are Australian Shepherds particularly susceptible to this gene mutation compared to other breeds? The MDR1 gene mutation (specifically a deletion mutation) is highly prevalent in Australian Shepherds, along with several other collie-type breeds (e.g., Collies, Shetland Sheepdogs, Border Collies). It’s estimated that a significant percentage of Australian Shepherds carry at least one copy of the mutated gene. This is due to a common ancestor in these herding breeds where the mutation originated and was passed down.

2. What exactly does the MDR1 gene do in a dog’s body?

   • How does the normal MDR1 gene function? A normal MDR1 gene produces a functional P-glycoprotein. This protein acts like a pump, located in cell membranes, particularly in the blood-brain barrier, intestines, kidneys, and liver. Its job is to pump certain drugs and toxins out of cells and out of the brain, preventing their accumulation to harmful levels.

   • How does the mutation impair this function? The MDR1 mutation results in a dysfunctional or non-functional P-glycoprotein. Without this effective pump, certain drugs can more easily cross the blood-brain barrier and accumulate to toxic levels in the central nervous system, leading to severe neurological symptoms, and sometimes even death.

3. Which common medications are problematic for Australian Shepherds with the MDR1 mutation?

   • Can you list some of the most critical drugs to avoid or use with caution?

     • Ivermectin: A common antiparasitic (heartworm preventative in low doses, but higher doses for other parasites can be toxic).

     • Loperamide (Imodium®): An anti-diarrheal medication.

     • Acepromazine: A sedative and tranquilizer.

     • Butorphanol: An opioid pain reliever and sedative.

     • Vincristine, Vinblastine, Doxorubicin: Chemotherapy drugs.

     • Erythromycin: An antibiotic.

     • Cyclosporin: An immunosuppressant.

   • Are there over-the-counter products or supplements that might also pose a risk? While less common, some over-the-counter products or herbal supplements could theoretically interact, though research is less extensive. It’s always best to consult your veterinarian about any medication or supplement for an MDR1-affected dog.

4. What are the potential symptoms if an MDR1-affected Australian Shepherd is exposed to a problematic drug?

   • What kind of reactions might I observe? Symptoms are typically neurological and can include:

     • Lethargy, depression, excessive drooling

     • Ataxia (lack of coordination, stumbling)

     • Blindness

     • Tremors, seizures

     • Coma

     • In severe cases, death.

   • How quickly do symptoms typically appear? Symptoms can appear within hours to a day after exposure, depending on the drug and the dosage.

5. How can I get my Australian Shepherd tested for the MDR1 mutation?

   • What kind of test is it (e.g., blood test, cheek swab)? It’s a DNA test, usually performed using a cheek swab (buccal swab) or a blood sample. Both methods are highly accurate.

   • Where can I get my dog tested? You can order a test kit directly from specialized canine genetic testing laboratories (e.g., Embark, Optimal Selection, Paw Print Genetics, GenSol Diagnostics) or ask your veterinarian to collect the sample and send it to a lab for you.

6. What do the MDR1 test results (N/N, M/N, M/M) mean for my Australian Shepherd?

   • N/N (Normal/Normal): This indicates the dog has two normal copies of the MDR1 gene. They are not affected by the mutation and will not pass it on to their offspring. They can safely receive all medications.

   • M/N (Mutant/Normal) or Heterozygous: This indicates the dog has one normal copy and one mutated copy of the MDR1 gene. They are considered “carriers” or “affected” to some degree. While they may tolerate some drugs at normal doses, they can be sensitive to certain medications, often requiring reduced dosages or alternative drugs. They will pass the mutated gene on to approximately 50% of their offspring.

   • M/M (Mutant/Mutant) or Homozygous Affected: This indicates the dog has two mutated copies of the MDR1 gene. They are highly sensitive to problematic drugs and are at a very high risk of severe reactions if given contraindicated medications. They will pass the mutated gene on to 100% of their offspring.

7. Does an Australian Shepherd with the MDR1 mutation need specialized veterinary care?

   • What precautions should my veterinarian take? Yes. Your veterinarian should be informed of your dog’s MDR1 status. They will need to adjust dosages of certain drugs or select alternative medications that are not affected by the MDR1 gene.

   • Should I always inform new vets about my dog’s MDR1 status? Absolutely. This information should be clearly noted in your dog’s medical records and verbally communicated to any new veterinarian or emergency clinic personnel. Consider having a tag or medical alert on your dog that states their MDR1 status.

8. How does MDR1 status affect breeding decisions for Australian Shepherds?

   • Can two carriers (M/N) be bred together? What are the risks? Breeding two M/N dogs carries a 25% chance of producing M/M (affected) puppies, a 50% chance of M/N (carrier) puppies, and a 25% chance of N/N (clear) puppies. This type of breeding is generally discouraged if the goal is to reduce the incidence of the mutation.

   • Should an affected (M/M) dog ever be bred? Most responsible breeders would advise against breeding an M/M dog due to the certainty of passing on a mutated gene to all offspring, increasing the mutation’s prevalence.

   • What are the recommendations for reducing the prevalence of the MDR1 mutation in the breed? The ideal breeding practice is to breed N/N dogs to N/N dogs. If an M/N dog must be bred (e.g., for other exceptional qualities), it should only be bred to an N/N dog. This ensures no M/M puppies are produced, and all puppies will be either N/N or M/N. Genetic testing of all breeding stock is paramount.

9. If my Australian Shepherd has the MDR1 mutation, can they still live a normal, healthy life?

   • What is the prognosis for affected dogs with proper management? Yes, absolutely! With proper management and careful veterinary oversight (avoiding problematic drugs or adjusting doses), Australian Shepherds with the MDR1 mutation can live full, normal, and healthy lives without any issues directly related to the mutation itself.

   • Are there any long-term health implications beyond drug sensitivity? No, the MDR1 mutation primarily affects how a dog metabolizes and handles certain drugs. It does not cause health problems in the absence of exposure to those drugs.

10. Is there a cure or treatment for MDR1 sensitivity?

    • Can the gene mutation be reversed or “fixed”? No, there is no cure or way to “fix” the genetic mutation itself. It is a permanent part of the dog’s genetic makeup.

    • What can be done if my dog accidentally receives a problematic medication? If a dog with the MDR1 mutation is exposed to a toxic dose of a problematic drug, immediate veterinary intervention is critical. Treatment focuses on supportive care to manage symptoms, potentially including detoxification methods like activated charcoal, IV fluids, and medications to control seizures or other neurological signs.