There are a few breeds affected by "MDR1", Aussies are one of them, what does this mean? Mostly it's important for your Veterinary Dr. to know about this, as it pertains to the types of drugs that Aussies(and other herding breeds) are sensitive to. MDR1 stands for Multi-Drug Resistance 1.

Here are a couple of great links to read up on for more detailed information.

http://www.ashgi.org/home-page/genetics-info/faq/mdr1-faqs

http://vcpl.vetmed.wsu.edu/

Taken Directly from VETMED.wsu.edu

Many herding breed dogs have a genetic predisposition to adverse drug reactions involving over a dozen different drugs. The most serious adverse drug reactions involve several antiparasitic agents (ivermectin, milbemycin and related drugs), the antidiarrheal agent loperamide (Imodium), and several anticancer drugs (vincristine, doxorubicin, others). These drug sensitivities result from a mutation in the multidrug resistance gene (MDR1 gene). At Washington State University's College of Veterinary Medicine you can test your dog for multidrug sensitivity and prevent serious adverse drug reactions. We can work with your dog’s veterinarian to find appropriate drug doses or alternative drugs for your dog based on results of MDR1 testing.

The Partnership for Preventive Healthcare, is an initiative jointly sponsored by the American Animal Hospital Association and the American Veterinary Medical Association. Together the two associations offer a set of Canine and Feline Preventive Healthcare Guidelines. One of the important recommendations is that dog owners use genetic testing—like the MDR1 test —as part of an overall healthcare plan for their pets.

"antiparasitic agents" include your dewormer, and if you live on a farm, the things that you would use to deworm sheep, horse and cattle.

a list of drugs to stay away from

http://vcpl.vetmed.wsu.edu/problem-drugs

List taken Directly from this^ website

Drugs that have been documented to cause problems in dogs with the MDR1 mutation include:

• 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.

Consider sharing this information with your Veterinarian so that they may proceed cautiously, as your puppy is at the very least what we call "affected" or mutant/normal, although it is safer to assume that each puppy is Mutant/Mutant as Lois is.

I hope you found this information helpful! Please feel free to ask any questions here should you have any!