Medetomidine immobilisation and atipamezole reversal in large estuarine crocodiles (Crocodylus porosus) using metabolically scaled dosages.

Abstract

BACKGROUND: Restraint of large estuarine crocodiles is potentially dangerous. Neuromuscular blockers and other immobilising drugs have been used with variable results. Medetomidine has been reported as a reliable, repeatable and reversible immobilisation agent in small estuarine crocodilians. METHODS AND RESULTS: Two wild and two farmed male animals, between 3.05 and 4.6 m long, were hand-injected into a triceps muscle with a metabolically scaled medetomidine dosage. Immobilisation occurred within 30 min. At the conclusion of the procedures, 70 min after medetomidine administration, three animals were injected with atipamezole IM into the opposite triceps muscle at a dosage based on body surface area. Reversal occurred within 5 min. The fourth animal was intubated prior to reversal of medetomidine and maintained on isoflurane anaesthesia for a gastrotomy. All animals were monitored closely post recovery and then regularly for at least 1 week. CONCLUSIONS: Medetomidine at a metabolically scaled dosage delivered IM into the forelimb was effective for immobilising large estuarine crocodiles for at least 40 min. Atipamezole administered at a dosage calculated as a function of surface area effectively reversed this immobilisation.