Which synthetic opioid is used for immobilization of wildlife via projectile dart and requires naloxone on hand?

• A. Carfentanil
• B. Buprenorphine
• C. Diphenoxylate
• D. Etorphine

Answer: (A)

Immobilizing wildlife with a remote-delivered opioid relies on an ultra-potent mu-opioid agonist, so the ability to reverse the effects quickly is a critical safety feature. Carfentanil is a fentanyl analog far more potent than morphine, so only minute volumes are needed to induce immobility in large animals. Because of this extreme potency, the risk of respiratory depression and overdose is real, making it essential to have naloxone ready to reverse effects if needed. Buprenorphine wouldn’t produce full immobilization due to its partial agonist activity and ceiling effect, and diphenoxylate isn’t an immobilizing agent. Etorphine is also used for large-animal darts, but carfentanil’s particular use in very large wildlife and its strong emphasis on immediate reversal with naloxone explains why it’s the best answer here.