Immobilization of black bears (Ursus americanus) with orally administered carfentanil citrate

Ten black bears (Ursus americanus) were immobilized with orally administered carfentanil citrate. The total carfentanil dose was mixed with 5 to 20 ml honey and given incrementally to captive bears. The bears ranged in weight from 80 (estimated) to 233 kg. Total carfentanil doses ranged from 0.7 to 3.0 mg, resulting in dosages of 6.8 to 18.8 micrograms carfentanil/kg. Mean (+/- SD) times from estimated 80% mixture consumption to sternal recumbency, and first safe human contact were 7.7 +/- 2.3 min and 19.7 +/- 5.6 min, respectively. Undesired side effects of immobilization were muscle rigidity, bradypnea, and oxygen desaturation. All bears received diazepam to alleviate muscle rigidity and were insufflated with oxygen during immobilization. Nine immobilizations were considered satisfactory or good. The bear receiving 6.8 micrograms carfentanil/kg, the lowest dosage used, was very excited during induction and required intravenous (IV) ketamine to permit safe examination. Immobilization was reversed with 100 mg naltrexone/mg carfentanil administered (75% subcutaneous, 25% IV). Bears recovered to full mobility in 6.3 +/- 1.9 min. Five bears vomited post-recovery but no episodes of renarcotization were observed.