Xylazine hydrochloride-ketamine hydrochloride immobilization of wolves and its antagonism by tolazoline hydrochloride.

Fourteen wolves (Canis lupus L.) were singularly or repeatedly immobilized with 30 mg xylazine hydrochloride (HCl) and 400 mg ketamine HCl. Mean induction time was 5.3 +/- 4.6 min (mean +/- SD). Administration of 8.0 mg/kg tolazoline HCl as an antagonist significantly reduced immobilization times from 148.0 +/- 52.7 to 47.9 +/- 8.9 min (F = 63.69, df = 1,17, P less than 0.05). The average times from injection to ambulation for 2.0, 4.0, and 8.0 mg/kg tolazoline HCl were 35.2 +/- 31.8, 18.5 +/- 11.7, and 10.2 +/- 9.1 min. Tolazoline HCl increased heart rates significantly (P less than 0.001) from 75 +/- 14 to 120 +/- 23 beats/min, reversing a xylazine HCl-induced bradycardia. Respiratory rates also increased significantly (P less than 0.01) after tolazoline HCl injection from 19 +/- 7 to 28 +/- 8 breaths/min. Immobilization resulted in an initial hypertension which was normalized after tolazoline HCl administration. One female wolf had a single sinoatrial block within 1 min of receiving tolazoline HCl. Tolazoline HCl appears to be an effective antagonist for xylazine HCl-ketamine HCl immobilization of wolves.