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


Jack-Yves Deschamps, Emergency and Critical Care Unit, LUNAM University, ONIRIS, Nantes-Atlantic College of Veterinary Medicine, Food Science and Engineering – La Chantrerie, BP 40706, 44 307 NANTES, France. E-mail:


Case history and presentation  Two non-human primates (Macaca fascicularis), weight 3.5 kg, enrolled in an experimental protocol received a 25 μg 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 μg L−1) confirmed fentanyl overdose.

Conclusions  This report of two fatal intoxications in non-human primates secondary to ingestion of a transdermal fentanyl patch demonstrates that this method of analgesia is inappropriate for non-human primates, because of their tendency to chew almost anything they can reach.