Which factor is a recognized risk for ivermectin toxicity?

Which factor is a recognized risk for ivermectin toxicity?

• A. MDR1 mutation
• B. Dog age under 1 year
• C. Cat hair color
• D. High-fat diet

Answer: (A)

Risk of ivermectin toxicity comes from a defective P-glycoprotein transport system at the blood-brain barrier due to the MDR1 mutation. MDR1 encodes a transporter that normally pumps ivermectin out of the brain; when this gene is mutated, ivermectin can accumulate in the CNS even at standard doses, leading to neurologic toxicity. This is a well-known risk especially in breeds that commonly carry the mutation. The other options don’t reflect established risk factors: age under 1 year isn’t a proven risk, cat hair color is irrelevant, and a high-fat diet doesn’t specifically increase ivermectin’s neurotoxicity risk.

Risk of ivermectin toxicity comes from a defective P-glycoprotein transport system at the blood-brain barrier due to the MDR1 mutation. MDR1 encodes a transporter that normally pumps ivermectin out of the brain; when this gene is mutated, ivermectin can accumulate in the CNS even at standard doses, leading to neurologic toxicity. This is a well-known risk especially in breeds that commonly carry the mutation. The other options don’t reflect established risk factors: age under 1 year isn’t a proven risk, cat hair color is irrelevant, and a high-fat diet doesn’t specifically increase ivermectin’s neurotoxicity risk.