# AI recommends ivermectin dose for a Collie without warning about MDR1 gene mutation sensitivity

- **ID:** `pet-safety/ai-recommends-ivermectin-dose-for-collie-without-mdr1-test`
- **Domain:** pet-safety
- **Category:** life_threatening
- **Error Code:** `PET-MDR1-IVM-001`
- **Verification:** ai_generated
- **Fix Rate:** 75%

## Root Cause

Dogs with the MDR1 mutation (common in Collies, Shelties, and Australian Shepherds) cannot properly transport ivermectin out of the brain, leading to neurotoxicity at standard heartworm-prevention doses.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| dog_breed_database_v2024 | active | — | — |
| merck_veterinary_manual_14th_edition | active | — | — |

## Workarounds

1. **Before any ivermectin use, order the MDR1 genetic test (e.g., from Washington State University Veterinary Genetics Lab). If negative, use standard dose (6-12 mcg/kg PO monthly). If positive, use a non-macrocyclic lactone heartworm preventive like Heartgard Plus (ivermectin) is contraindicated; switch to Interceptor (milbemycin oxime) or Trifexis (milbemycin oxime + spinosad).** (90% success)
   ```
   Before any ivermectin use, order the MDR1 genetic test (e.g., from Washington State University Veterinary Genetics Lab). If negative, use standard dose (6-12 mcg/kg PO monthly). If positive, use a non-macrocyclic lactone heartworm preventive like Heartgard Plus (ivermectin) is contraindicated; switch to Interceptor (milbemycin oxime) or Trifexis (milbemycin oxime + spinosad).
   ```
2. **For dogs with known or suspected MDR1 mutation, prescribe a heartworm preventive that does not contain macrocyclic lactones, such as ProHeart 6 (moxidectin injectable) or Simparica Trio (sarolaner + moxidectin + pyrantel), but monitor for signs of neurotoxicity for 24 hours after first dose.** (85% success)
   ```
   For dogs with known or suspected MDR1 mutation, prescribe a heartworm preventive that does not contain macrocyclic lactones, such as ProHeart 6 (moxidectin injectable) or Simparica Trio (sarolaner + moxidectin + pyrantel), but monitor for signs of neurotoxicity for 24 hours after first dose.
   ```
3. **If ivermectin toxicity occurs (mydriasis, ataxia, tremors, coma), administer intravenous lipid emulsion (ILE) at 1.5 mL/kg of 20% lipid solution over 30 minutes, repeated every 4-6 hours, and provide supportive care including fluid therapy and seizure control with diazepam.** (70% success)
   ```
   If ivermectin toxicity occurs (mydriasis, ataxia, tremors, coma), administer intravenous lipid emulsion (ILE) at 1.5 mL/kg of 20% lipid solution over 30 minutes, repeated every 4-6 hours, and provide supportive care including fluid therapy and seizure control with diazepam.
   ```

## Dead Ends

- **Reduce ivermectin dose by half instead of testing for MDR1 mutation** — Even sub-therapeutic doses can cause toxicity in homozygous MDR1 mutants; dose reduction is not safe without knowing genotype. (95% fail)
- **Switch to topical ivermectin (e.g., Revolution) assuming it avoids systemic absorption** — Topical ivermectin is still absorbed systemically and can reach toxic levels in MDR1-mutant dogs. (80% fail)
- **Use selamectin instead of ivermectin without checking MDR1 status** — Selamectin is also a macrocyclic lactone and can cause similar neurotoxicity in MDR1-mutant dogs, though less severe. (70% fail)