Opioid‐Induced Myoclonus During Premedication in Two Dogs With Hydrocephalus Proactively Managed With Antiepileptic Medications

This report describes opioid-induced neurotoxicity (OIN) in two dogs with hydrocephalus undergoing the investigation of recurrent seizures; in both dogs, myoclonus occurred following premedication with butorphanol and remifentanil and resolved following the administration of midazolam. Thorough clinical evaluation excluded underlying systemic disease and increased intracranial pressure as possible causes, and opioid-induced modulation of gamma-aminobutyric acid (GABA) inhibitory and dopaminergic interneurons was assumed. Benzodiazepines, like midazolam, enhanced GABA and appeared to be effective in managing these symptoms. The findings suggest that even at therapeutic doses, certain opioids can cause OIN in dogs. Caution is advised when using opioids, particularly in dogs with pre-existing central nervous system disorders, and further research is needed to better understand dosage effects and alternative treatment options for OIN prevention.