Pancuronium Bromide for Chemical Immobilization of Adult Nile Crocodiles (Crocodylus niloticus): A Field Study

(1) Background: Pancuronium bromide is a neuromuscular blocker used for immobilizing crocodiles that can be reversed with neostigmine. A recommended drug dose has only been established for saltwater crocodiles (Crocodylus porosus), mostly based on trials in juveniles and subadults. After trialing a dose recommendation in a small cohort of nine Nile crocodiles (Crocodylus niloticus), we developed and applied a new dose recommendation for large adult Nile crocodiles. (2) Methods: we trialed and adapted a pancuronium bromide (Pavulon 4 mg/2 mL) dose in Nile crocodiles originally established for saltwater crocodiles and applied the new dose for the immobilization of 32 Nile crocodiles destined for transport. Reversal was achieved with neostigmine (Stigmine 0.5 mg/mL). (3) Results: Nine crocodiles were included in the trial phase; the induction time was highly variable (average: 70 min; range: 20-143 min), and the recovery time was prolonged (average: 22 h; range: 50 min-5 days), especially in large animals after reversal with neostigmine. Based on these results, we established a dose-independent recommendation (3 mg pancuronium bromide and 2.5 mg neostigmine) for animals weighing ≥ 270 kg (TL ≥ ~3.8 m). When applied to 32 adult male crocodiles (BW range: 270-460 kg; TL range: 3.76-4.48 m), the shortest induction time was ~20 min and the longest ~45 min. (4) Conclusions: Pancuronium bromide and its antidote, neostigmine, are effective for the immobilization and reversal of adult male Nile crocodiles (TL ≥ 3.8 m or BW ≥ 270 kg) when given in a weight-independent fashion.