[Milbemycinoxime intoxication in a Miniature Australian Shepherd dog]

Area of Science:

• Veterinary Neurology
• Pharmacogenomics

Background:

• Milbemycin oxime is commonly used for parasiticides in dogs.
• MDR1-gene mutations affect drug metabolism and can increase sensitivity to certain medications.
• Previous understanding suggested milbemycin oxime was safe for MDR1-deficient dogs.

Observation:

• A 3-year-old Miniature Australian Shepherd, homozygous for the MDR1-gene mutation, presented with status epilepticus post-milbemycin oxime administration.
• The dog required mechanical ventilation for aspiration pneumonia and prolonged propofol infusion for seizure control.
• Full recovery was achieved by day 10.

Findings:

• The case demonstrates that milbemycin oxime can induce severe neurological adverse events in MDR1-deficient dogs, contrary to prior assumptions.
• Homozygosity for the MDR1-gene mutation may predispose dogs to severe toxicity from milbemycin oxime.

Implications:

• Clinicians should consider the MDR1-gene mutation status when prescribing milbemycin oxime.
• Lowest possible dosages of milbemycin oxime are recommended for MDR1-deficient dogs.
• Pet owners should be informed about potential severe complications associated with milbemycin oxime in genetically susceptible dogs.