The drug list
Which drugs matter for MDR1 dogs?
16drugs with documented MDR1 relevance, grouped by how WSU classifies them. Every entry links to its primary source. Drugs we couldn't confirm against a live primary source are listed at the bottom as omitted — not invented.
Avoid in MDR1-affected dogs
WSU advises avoiding these drugs in all dogs with the mutation.
- LoperamideImodium — over-the-counter antidiarrhoealAvoid in all dogs with the MDR1 mutationWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
Dose-tier dependent
Safe at the heartworm-prevention dose, dangerous at much higher doses.
- IvermectinHeartgard, Iverhart — heartworm preventive & antiparasiticSafe at heartworm-prevention dose · dangerous at high (mange) dosesWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- MilbemycinInterceptor, Sentinel — heartworm preventiveSafe at label (heartworm-prevention) dose · toxic at much higher dosesWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- MoxidectinProHeart, Advantage Multi, Simparica Trio — heartworm preventiveSafe at label (heartworm-prevention) dose · toxic at much higher dosesWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- SelamectinRevolution — topical parasiticideSafe at label (heartworm-prevention) dose · toxic at much higher dosesWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
Caution — reduced dose or vet consultation
Affected dogs are more sensitive; doses are reduced or confirmed with your vet.
- Acepromazinetranquilizer / pre-anaesthetic sedativeUse a reduced dose — affected dogs are more sensitiveWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- Apomorphineemetic — used to induce vomiting after a toxin is ingestedConfirm dosing with your vet for MDR1-affected dogsWSU — MDR1 in Dogs (current drug & breed hub)
- ButorphanolTorbugesic — opioid analgesic & pre-anaestheticUse a reduced dose — affected dogs are more sensitiveWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- CyclosporineAtopica — immunosuppressant (allergic skin disease, immune disease)Confirm dosing with your vet for MDR1-affected dogsWSU — MDR1 in Dogs (current drug & breed hub)
- Doxorubicinchemotherapy agentReduced dose needed under oncology supervisionWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- GrapiprantGalliprant — anti-inflammatory (osteoarthritis pain)Confirm dosing with your vet for MDR1-affected dogsWSU — MDR1 in Dogs (current drug & breed hub)
- MaropitantCerenia — anti-nausea / antiemeticConfirm dosing with your vet for MDR1-affected dogsWSU — MDR1 in Dogs (current drug & breed hub)
- OndansetronZofran — anti-nausea / antiemeticConfirm dosing with your vet for MDR1-affected dogsWSU — MDR1 in Dogs (current drug & breed hub)
- Paclitaxelchemotherapy agentReduced dose needed under oncology supervisionWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- Vinblastinechemotherapy agentReduced dose needed under oncology supervisionWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
- Vincristinechemotherapy agent (lymphoma, other cancers)Reduced dose needed under oncology supervisionWSU — Is your pet at risk of an adverse reaction to common drugs? (dose tiers, genotypes, signs)
This is general information, not veterinary advice for your dog. It does not diagnose or prescribe. Always discuss any medication decision with your veterinarian before acting — they know your dog's full picture, including its MDR1 status if it has been tested. See our disclaimer and how we research.
Drugs we deliberately left out (for now)
These appear in secondary literature as MDR1-relevant, but we could not confirm them against a current, live WSU primary source during our last verification. Rather than guess on a health-critical claim, we omit them until they can be cite-pinned.
- Erythromycin — Appears in older VCPL lists / secondary literature as a P-glycoprotein substrate, but could not be confirmed on a current live WSU URL during our 2026-06-16 verification. Omitted until cite-pinned.
- Domperidone — Same as erythromycin — not confirmed on a current live WSU URL. Omitted until cite-pinned.
- Actinomycin-D (dactinomycin) — A chemotherapy P-glycoprotein substrate cited in secondary sources, but not confirmed on a current live WSU URL. Omitted until cite-pinned.
See our methodology and sources for how we handle this.