MDR1 Gene Mutation in Dogs

Multidrug Sensitivity in Dogs

Many herding dog breeds are afflicted with a mutation of the multidrug resistance (mdr1) gene. This gene encodes a protein (P-glycoprotein) that is responsible for removing certain drugs and toxins from the brain.

Dogs that carry the mdr1 genetic defect cannot rid their brains of the problem drugs. The result is a neurotoxic buildup that can cause abnormal neurological symptoms and/or death. Research has shown that three of every four Collies have at least one copy of the mutated gene.

There is now a test available to screen for the presence of the mutated mdr1 gene.

Drugs to Avoid for Dogs with MDR1

Drugs to avoid in dogs with the MDR1 gene mutation: The tranquilizer acepromazine; a pain medication called butorphanol; the anti-cancer drugs doxorubicin, vinblastine and vincristine; the antibiotics erythromycin and rifampin; anti-parasitic drugs such as ivermectin (in high doses), milbemycin, moxidectin and selamectin; and the anti-diarrheal drug loperamide (Imodium).