Effectiveness of tolazoline in reversing xylazine-induced sedation in calves.
OBJECTIVE
To test effectiveness of IV administration of tolazoline hydrochloride in reversing xylazine hydrochloride-induced sedation in calves.


METHODS
Prospective study.


METHODS
12 female and 12 male Friesian-cross calves from 5 to 7 months old.


METHODS
Calves were assigned to 1 of 4 treatment groups. Calves were given xylazine (0.3 mg/kg [0.14 mg/lb] of body weight, IM). Twenty minutes later, calves were treated with saline (0.9% NaCl) solution (1 ml/50 kg [1 ml/110 lb], IV) or tolazoline (1, 2, or 4 mg/kg [0.45, 0.9, or 1.8 mg/lb], IV). Behavioral and physiologic measurements included elapsed time from xylazine administration to recumbency, arousal and standing times after reversal drug administration, heart rate, and respiratory rate.


RESULTS
Mean (+/- SD) recumbency time for all calves was 5.4 +/- 1.8 minutes. Compared with administration of saline solution, all 3 doses of tolazoline significantly decreased arousal and standing times. Mean arousal time for calves receiving saline solution was 27.8 +/- 11.5 minutes. Administration of tolazoline at 1, 2, and 4 mg/kg resulted in mean arousal times of 4.7 +/- 3.8, 0.9 +/- 0.5, and 0.7 +/- 0.3 minutes, respectively. Mean standing time for calves receiving saline solution was 38.8 +/- 2.8 minutes. Administration of tolazoline at 1, 2, and 4 mg/kg resulted in mean standing times of 14.0 +/- 11.0, 3.0 +/- 1.2, and 2.4 +/- 1.1 minutes, respectively.


CONCLUSIONS
For routine use, tolazoline doses of 1 to 2 mg/kg should suffice. In cattle, IV administration of tolazoline reverses pharmacologic effects of xylazine, thereby hastening recovery from xylazine-induced sedation.
Powell
J D
JD
Auckland Veterinary Centre, Takanini, New Zealand.
Denhart
J W
JW
Lloyd
W E
WE
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001143:Arousal / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D005260:Female; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D013997:Time Factors; D014043:Tolazoline / Q000008:administration & dosage / Q000494:pharmacology*; D014991:Xylazine / Q000008:administration & dosage / Q000037:antagonists & inhibitors*
D000317:Adrenergic alpha-Antagonists; D006993:Hypnotics and Sedatives; D014991:Xylazine; D014043:Tolazoline