Antagonistic effect of atipamezole on xylazine-induced sedation, bradycardia, and ruminal atony in calves
1991
Thompson, J.R. | Kersting, K.W. | Hsu, W.H.
Three doses of an alpha2-adrenoreceptor antagonist, atipamezole, were administered to reverse xylazine-induced sedation, bradycardia, and ruminal atony in calves. Once a week for 4 weeks, each of 6 calves was administered IV 1 treatment of:0.3 mg of xylazine/kg of body weight, followed in 10 minutes by 1 ml of 0.9% NaCl; 0.3 mg of xylazine/kg, followed in 10 minutes by 3 microgram of atipamezole/kg; 0.3 mg of xylazine/kg, followed in 10 minutes by 10 microgram of atipamezole/kg; or 0.3 mg of xylazine/kg, followed in 10 minutes by 30 microgram of atipamezole/kg. The order of the 4 treatments in each calf was selected at random. Xylazine alone caused lateral recumbency for 33.6 +/- 7.1 minutes (mean +/-SEM). Atipamezole administered at dosages of 3, 10, and 30 microgram/kg shortened xylazine-induced lateral recumbency to 20.5 +/- 3.0, 10.2 +/- 0.2, and 9.3 +/- 0.5 minutes, respectively. Calves given xylazine alone stood at > 60 minutes after the onset of recumbency. Atipamezole given at 3, 10, and 30 microgram/kg shortened the time from onset of lateral recumbency to standing to 40.2 +/- 6.9, 12.8 +/- 1.1, and 10.0 +/- 0.7 minutes, respectively. Drowsiness was found in calves given the lowest dosage of atipamezole (3 microgram/kg) after the calves stood. Atipamezole given at dosages of 10 and 30 microgram/kg reversed xylazine-induced ruminal atony in a dose-dependent manner. In addition, 30 microgram of atipamezole/kg reversed xylazine-induced bradycardia, but the lower dosages of this antagonist did not. Results indicated that 30 microgram of atipamezole/kg should be a useful antidote for xylazine overdose in cattle.
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