What if you could know—before you ever give a pill—whether your dog or cat is likely to have a bad reaction? In this episode, Dr. Alice and Janet sit down with Dr. Katrina Mealey, Associate Dean for Research at Washington State University’s College of Veterinary Medicine, NIH-funded researcher, and Inventor of the Year for her groundbreaking genetic test that flags pets at risk for serious adverse drug reactions.
Dr. Mealey explains the science in plain English: a natural “gatekeeper” protein called P-glycoprotein (coded by the MDR1 gene) protects the brain and body by pumping out potentially toxic compounds. When a pet carries certain MDR1 mutations, many common medications—prescription and OTC—can reach dangerous levels. We cover how the cheek-swab test works, how to get it for your pet, which breeds are most affected, why dosage matters so much, and how new vet-friendly tools help tailor safer treatments.
In this episode:
- MDR1 101: What P-glycoprotein does and why it’s the body’s drug “gatekeeper.”
- Who’s at risk: Collies (~75%), Australian & English Shepherds (~50%), plus surprises like Boxers, Huskies, and even the occasional Golden—plus the feline version discovered in 2015.
- Real-world reactions: From anti-diarrheals and chemo agents to certain flea preventives—how problems present and what vets should watch for.
- Testing made easy: Simple cheek swab or blood test; results emailed to you and your vet.
- Dosing guidance: Meet MDR1Caddie (dogs) and WhisPurr (cats)—information that suggests dose adjustments based on whether a pet has one or two copies of the mutation.
- Myth-busting ivermectin: Why tiny monthly heartworm doses are different from mange/cancer “DIY” dosing—and why self-medicating is dangerous.
- Take-home for pet parents: Bring MDR1 status up with your vet before surgeries, chemo, dermatology meds, new preventives, or simple OTC medications like Immodium.
About our guest
Dr. Katrina Mealey is a veterinarian, pharmacist, researcher, and author (editor of Pharmacotherapeutics for Veterinary Dispensing). Her lab identified the MDR1 mutation in dogs and later in cats, and continues to map which drugs interact with P-glycoprotein so veterinarians can treat more safely.
https://vetmed.wsu.edu/our-team/wsu-profile/kmealey/
Resources & links
- MDR1 genetic test: Link in show notes to order a cheek-swab kit for dogs or cats.
- Drug interaction updates: Ongoing lists and guidance are available via the testing program (see show notes).
- Dose-adjustment information: MDR1Caddie (dogs) and WhisPurr(cats).
- Talk to your veterinarian before starting, stopping, or changing any medication.
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Support our sponsor for this episode Blue Buffalo by visiting bluebuffalo.com. BLUE Natural Veterinary Diet formulas offer the natural alternative in nutritional therapy. At Blue Buffalo, we have an in-house Research & Development (R&D) team with over 300 years’ experience in well-pet and veterinary therapeutic diets, over 600 scientific publications, and over 50 U.S. patents. At Blue Buffalo, we have an in-house Research & Development (R&D) team with over 300 years’ experience in well-pet and veterinary therapeutic diets, over 600 scientific publications, and over 50 U.S. patents.
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All footage is owned by SLA Video Productions.