Everything You Need to Know About MDR1 for Australian Mountain Dogs & Doodles
MDR1 & Your Puppy – What You Really Need to Know
At Stokeshire, your puppy’s health and happiness are always our top priority. You may hear us mention the MDR1 gene, and we want you to feel completely at ease knowing that it’s something we plan for, manage, and educate you on—so you can focus on enjoying life with your new best friend.
What Is MDR1?
The MDR1 gene affects how a dog’s body processes certain medications. Some dogs with this gene are more sensitive to a small group of drugs. It’s not an illness, and it doesn’t affect your dog’s quality of life—it just means we’re extra thoughtful about the medications we choose.
Why You Don’t Need to Worry
Everyday care is safe – Routine vet visits, vaccinations, deworming, flea/tick prevention, spay/neuter, and dental care can all be done safely.
The “watch list” is short – Only certain drugs, often in very high doses or for very specific conditions, are a concern.
Easy to manage – A simple one-time DNA test tells you your dog’s MDR1 status. Once you know it, you just share it with your vet.
How We Set You Up for Success
We only use MDR1-safe protocols with our puppies.
We give you a clear, simple medication guide to keep with your puppy’s records.
We offer testing options so you can know your dog’s MDR1 status for life.
What You Can Do as an Owner
Keep a note in your phone: “This dog may have the MDR1 gene—check safe medication list.”
Share the WSU MDR1 link with your vet: WSU MDR1 Drug List
Enjoy your dog – MDR1 awareness is about prevention, not limitation.
Bottom Line:
Owning a dog with possible MDR1 status is like owning a dog who shouldn’t eat chocolate—you just avoid certain things, and life goes on normally. With a little awareness, your dog can live a long, happy, adventurous life by your side.
What is MDR1?
MDR1, also known as the ABCB1 gene mutation, affects how a dog’s body processes certain medications.
Normal ABCB1 Gene: Produces a protein “pump” that removes specific drugs from sensitive areas like the brain.
Mutated ABCB1 Gene: The pump malfunctions, allowing drug levels to build up to toxic levels, which can be dangerous or even life-threatening.
Why It Matters: Australian Mountain Dogs and Doodles often have herding breed ancestry (e.g., Australian Shepherd, Collie) where MDR1 is more common. Even without visible herding traits, your dog could carry the mutation.
High-Risk Medication Categories
Antiparasitics – e.g., high doses of ivermectin
Sedatives – e.g., acepromazine
Gastroprotectants
Certain chemotherapy agents
Full, up-to-date list available from Washington State University:
WSU MDR1 Problem Drug List
MDR1 Drug Sensitivity – Quick Reference Guide
This guide summarizes common medications, their brand names, and recommendations for dogs with the MDR1 mutation. Always consult your veterinarian and MDR1Caddie™ for dosing guidance when needed.
| Drug (Active Ingredient) | Brand Name | Recommendation for MDR1 Dogs |
|---|---|---|
| Acepromazine | — | Contact MDR1Caddie™ for dosing recommendations. |
| Afoxolaner | NexGard | Tested safe; no increased risk for adverse effects. |
| Apomorphine | — | Contact MDR1Caddie™ for dosing recommendations. |
| Butorphanol | Torbugesic | Contact MDR1Caddie™ for dosing recommendations. |
| Chemotherapy Agents | Various | Contact MDR1Caddie™ for dosing recommendations. |
| Cyclosporine | Atopica | Contact MDR1Caddie™ for dosing recommendations. |
| Doxorubicin | — | See Chemotherapy. |
| Fluralaner | Bravecto | Tested safe; no increased risk for adverse effects. |
| Grapiprant | Galliprant | Contact MDR1Caddie™ for dosing recommendations. |
| Ivermectin | Heartgard Plus | Safe at label doses; avoid high-dose formulations unless cleared via MDR1Caddie™. |
| Loperamide | Imodium | Avoid entirely – can cause neurological toxicity in MDR1 dogs. |
| Milbemycin | Interceptor, Interceptor Plus | Safe at label doses; check other formulations with MDR1Caddie™. |
| Maropitant | Cerenia | Contact MDR1Caddie™ for dosing recommendations. |
| Moxidectin | ProHeart, Simparica Trio, NexGard Plus, Advantage Multi | Tested safe; no increased risk for adverse effects. |
| Ondansetron | — | Contact MDR1Caddie™ for dosing recommendations. |
| Sarolaner | Simparica | Tested safe; no increased risk for adverse effects. |
| Vinblastine | — | See Chemotherapy. |
| Vincristine | — | See Chemotherapy. |
| Vinorelbine | — | See Chemotherapy. |
| Selamectin | Revolution | Safe at label doses; no increased risk for adverse effects. |
Note: This summary is for informational purposes only. Always consult your veterinarian and use the WSU MDR1Caddie™ tool for the most current and accurate recommendations.
Best Heartworm & Parasite Prevention for MDR1 Dogs
These products are tested safe at label doses for MDR1-positive dogs and provide broad, reliable protection.
| Product | Active Ingredient | Safety for MDR1 Dogs | Notes |
|---|---|---|---|
| Interceptor | Milbemycin oxime | Safe at label doses; well‐tolerated even in MDR1 dogs [PMC] [Collielife] | Oral tablet; monthly preventative. |
| ProHeart / Advantage Multi (topical) | Moxidectin (plus imidacloprid in Advantage Multi) | Safe at label doses; high margin of safety in MDR1 dogs [PMC] [Collielife] [LabK9] | ProHeart is injectable (6- or 12-month); Advantage Multi is topical spot-on. |
| NexGard / NexGard Spectra | Afoxolaner (± milbemycin oxime) | Safe even at multiple doses in MDR1-deficient dogs [PMC] | Oral chewable; convenient combination for fleas + internal parasites. |
Genetic Test Results Explained
Normal/Normal (Clear) – No mutation, no increased sensitivity
Mutant/Normal (Carrier) – One copy; mild to moderate sensitivity
Mutant/Mutant (Affected) – Two copies; high risk for severe reactions
Signs of an MDR1 Reaction
Reactions usually occur after exposure to a problem drug. Symptoms may appear within hours to a couple of days:
Vomiting & diarrhea
Disorientation, tremors
Lethargy or extreme sedation
Seizures
Coma (in severe cases)
How It’s Diagnosed
Preemptive DNA test – Highly recommended before your dog ever needs risky medication.
Post-reaction diagnosis – Sometimes discovered after an unexpected severe reaction.
Prevention & Management
The good news: MDR1 is completely manageable with the right precautions.
Test your dog – A simple cheek swab can confirm their status.
Share results with your vet – Have it added to their permanent record.
Avoid or adjust risky medications – Safer alternatives are available.
MDR1 Owner Action Plan
(For Dogs with One or Two MDR1 Mutations)
Step 1 – Test & Tell
Test once – We can handle the DNA swab before your puppy goes home.
Tell your vet – Share results and save them in your dog’s medical file.
Step 2 – Avoid These Common MDR1 Problem Drugs
(Most relevant for family pets – not full WSU list)
Flea/Tick & Heartworm:
Avoid ivermectin-based preventatives in high doses.
Avoid spinosad (Comfortis®, Trifexis®) if paired with high-dose ivermectin.
Sedatives & Anesthesia:
Avoid acepromazine and butorphanol unless vet adjusts dosage.
Other:
Avoid high doses of loperamide (Imodium®).
Step 3 – Ask for These Safer Alternatives
Heartworm: Milbemycin (Interceptor®, Sentinel®) or moxidectin (Advantage Multi®)
Flea/Tick: Isoxazoline class (Bravecto®, NexGard®, Simparica®)
Sedation: Dexmedetomidine or other adjusted protocols
Diarrhea: Probiotics, bland diet, or non-MDR1 medications
Step 4 – Keep It Simple
One note in your phone: “Dog is MDR1 mutant – check WSU list before prescribing.”
One printed copy of the WSU drug list in your dog’s folder.
One conversation with your vet = lifetime safety.
Farm & Working Dog Tips
Avoid access to ivermectin-treated livestock manure or pastures after treatment.
Use alternative parasite prevention plans safe for MDR1 dogs.
Why These Are the Top Picks
Moxidectin (like Advantage Multi or ProHeart) offers a wider safety margin than ivermectin and is tolerated at very high doses in MDR1 dogs without neurologic effects Budget Vet Care+15PMC+15PMC+15.
Milbemycin oxime (Interceptor) is also safe at proper preventive doses in MDR1 dogs, though high concentrations can be toxic labk9.co.uk+14PMC+14Veterinary Partner+14.
Afoxolaner, the flea-control ingredient in NexGard, combined with milbemycin in Spectra, was tested for safety even in MDR1 homozygous dogs and showed no adverse reactions PMC.
Recommendation Summary
For the least effort and highest safety in MDR1-positive or sensitive dogs, here’s the plan:
For internal parasites & heartworm:
Use Interceptor (monthly oral milbemycin oxime) or Advantage Multi (monthly topical moxidectin + imidacloprid) for broad protection with high safety.For flea control:
NexGard (afoxolaner) monthly chewable is safe and effective. If you want combined coverage for both internal and external parasites, NexGard Spectra includes milbemycin and remains safe.
For MDR1–mutant dogs, the safest heartworm and parasite prevention options are Interceptor (milbemycin oxime), Advantage Multi (moxidectin spot-on), or NexGard Spectra (afoxolaner + milbemycin). These are proven safe at label doses, and offer broad protection with minimal risk.
Bottom Line:
Australian Mountain Dogs and Doodles are intelligent, athletic, and loving companions. MDR1 awareness ensures they stay healthy and safe for a lifetime of adventures.
Routine puppy deworming protocols with pyrantel, fenbendazole, and toltrazuril are safe for MDR1 carriers and affected puppies. Toxicity risks come from high-dose ivermectin or other problem drugs—not from the common treatments breeders use at the label dose. When in doubt, consult your veterinarian before administering any medication outside standard protocols.