Tissue Residue Levels of the Tranquilizer Combination of Butorphanol, Azaperone, and Medetomidine, and the Antagonists, Naltrexone, Atipamezole, and Tolazoline, in Black Bears (Ursus americanus) Postimmobilization.

The tranquilizer combination of butorphanol, azaperone, and medetomidine (BAM) has shown good efficacy for immobilization of wildlife, including black bears (Ursus americanus). BAM is antagonized with a combination of naltrexone and atipamezole. We immobilized 19 adult captive wild caught black bears and, except for three bears that were euthanized immediately, bears were recovered with naltrexone and atipamezole. Tissue residues (≥0.01 ppm) for the tranquilizers butorphanol, azaperone, and medetomidine were detected in liver and muscle of all three bears euthanized on day 0 postinjection (PI). Azaperone was not detected after 1 d PI. Residue for medetomidine was detected in two bears: in the liver 3 d PI and in the kidney 6 d PI. Butorphanol was reported in three bears: in fat 5 d PI, in kidney 6 d PI, and, surprisingly, in kidney, muscle, and fat 7 d PI. No tissue residues were detected in the three bears euthanized at 8 d PI. Tissue residues for the antagonists, naltrexone and atipamezole, were detected in bears euthanized 2 and 6 d PI, but not in tissues from animals euthanized at 7 or 8 d PI.