Fatal overdose after ingestion of a transdermal fentanyl patch in two non-human primates

Case history and presentation Two non-human primates (Macaca fascicularis), weight 3.5 kg, enrolled in an experimental protocol received a 25 lg hour )1 transdermal fentanyl patch for postoperative analgesia. The following day both animals were clinically normal, but after a new induction of anaesthesia with ketamine, they developed severe and prolonged respiratory distress, profound coma and myosis. Management and follow-up Attempted reversal with naloxone was ineffective. After several hours of ventilation, both primates eventually died, 7 and 15 hours after ketamine injection, respectively. In both cases, the patch was discovered in the animal’s cheek pouch. Subsequent fentanyl serum concentration measurements (8.29 and 14.80 l gL )1 )