MDR1 Multi-Drug Resistance Gene
Collies with a mutation of this gene may experience various levels of sensitivity to numerous drugs, to include death.
For that reason, we strongly recommend avoiding all drugs on the list below.
Please share a copy of the list with your veterinarian and ask that they place it in your dog’s file.
While we continue to work toward breeding dogs that are MDR1 normal/normal, it will take time and a commitment to breeding healthy dogs before we can breed the gene out. Regardless of the MDR1 status of the collie, if they have one copy of the mutation (normal/mutant), two copies (mutant/mutant), or are clear (normal/normal), we recommend NEVER giving a collie any drugs listed on the “dangerous” list provided below.
All collies from Glenelg Collies are screened and tested for the MDR1 mutation prior to breeding and prior to leaving for their new homes.
Drugs that have been documented to cause problems in dogs with the MDR1 mutation:
- Ivermectin (antiparasitic agent)- While the dose of ivermectin used to prevent heartworm infection is SAFE in dogs with the mutation (6 micrograms per kilogram), higher doses, such as those used for treating mange (300-600 micrograms per kilogram) will cause neurological toxicity in dogs that are homozygous for the MDR1 mutation (MDR1 mutant/mutant) and can cause toxicity in dogs that are heterozygous for the mutation (MDR1 mutant/normal).
- Selamectin, milbemycin, and moxidectin (antaparasitic agents)- Similar to ivermectin, these drugs are safe in dogs with the mutation if used for heartworm prevention at the manufacturer’s recommended dose. Higher doses (generally 10-20 times higher than the heartworm prevention dose) have been documented to cause neurological toxicity in dogs with the MDR1 mutation.
- Loperamide (ImodiumTM; antidiarrheal agent)- At doses used to treat diarrhea, this drug will cause neurological toxicity in dogs with the MDR1 mutation. This drug should be avoided in all dogs with the MDR1 mutation.
- Acepromazine (tranquilizer and pre-anesthetic agent)- Based on collaborative research, the VCPL has determined that dose reductions are required for dogs MDR1 mutant/mutant and MDR1 mutant/normal.
- Butorphanol (analgesic and pre-anesthetic agent)- Dose reduction required for dogs MDR1 mutant/mutant and MDR1 mutant/normal.
- Chemotherapy Agents (Vincristine, Vinblastine, Doxorubicin, Paclitaxel)- Based on collaborative research, the VCPL has determined that dose reductions are required for dogs MDR1 mutant/mutant and MDR1 mutant/normal in order to avoid SEVERE toxicity.
- Apomorphine – this drug is used to induce vomiting in dogs that have ingested poisons/toxins. It can cause central nervous system depression in dogs with the MDR1 mutation at standard doses.
FOR MORE INFORMATION/TESTING:
Washington State University (WSU): https://prime.vetmed.wsu.edu/
UC Davis: https://vgl.ucdavis.edu/test/multidrug-sensitivity-mdr1