Potentially Harmful Drugs

  • Antibiotics:  Erythromycin.
  • Antidiarrheal Agents:  Loperamide (Imodium)
  • Antiparasitic Agents:  Ivermectin, Selamectin, milbemycin, moxidectin, Emodepside (Profender)
  • Chemotherapy Agents:  Vincristine, Vinblastine, Doxorubicin
  • Pre-Anesthetic Agents:  Acepromazine, Butorphano

Lien Animal Clinic recommends testing dogs of herding breed ancestry to determine whether they carry the MDR1 gene. The information is extremely important to help your veterinarian determine which drugs are safe for your dog.  Testing at our clinic involves taking a small blood sample or cheek swab from your pet and submitting it to the WSU laboratory.  Results are received between 10-14 days after submission.

Many herding breed dogs, including collies and Australian shepherds, carry a genetic mutation that makes them very sensitive to certain drugs. Using these drugs on the affected breeds can cause serious neurological illness and even death.
Fortunately, there is a DNA test that will let you know whether your dog has this mutation by submitting a simple cheek swab or a blood sample. This test is performed at the Washington State University College of Veterinary Medicine and is extremely accurate in predicting drug sensitivity.
Simply put, MDR1 is a “multi drug resistance gene” which certain breeds (including those of mixed breed heritage) carry that causes sensitivity to certain drugs. Dogs that have this gene mutation lack a protein (P-glycoprotein) which is essential to clear the drug from the brain. This causes a build-up of the drug in the brain, which leads to toxicity and abnormal neurological symptoms and at times death, depending on the level of toxicity.
Dogs can have a single copy of the gene, which most often results in sensitivity and possibly milder reactions to the drug in question, or a double copy of the gene, leading to more severe reactions and toxicity. Even if your dog does not look like a herding breed, the mutation can still be there from previous generations.