Antagonistic effect of atipamezole on xylazine-induced sedation, bradycardia, and ruminal atony in calves.
Three doses of an alpha 2-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 micrograms of atipamezole/kg; 0.3 mg of xylazine/kg, followed in 10 minutes by 10 micrograms of atipamezole/kg; or 0.3 mg of xylazine/kg, followed in 10 minutes by 30 micrograms 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 micrograms/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 greater than 60 minutes after the onset of recumbency. Atipamezole given at 3, 10, and 30 micrograms/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 micrograms/kg) after the calves stood. Atipamezole given at dosages of 10 and 30 micrograms/kg reversed xylazine-induced ruminal atony in a dose-dependent manner. In addition, 30 micrograms of atipamezole/kg reversed xylazine-induced bradycardia, but the lower dosages of this antagonist did not. Results indicated that 30 micrograms of atipamezole/kg should be a useful antidote for xylazine overdose in cattle.
Thompson
J R
JR
Department of Veterinary Clinical Sciences, Iowa State University, Ames 50011.
Kersting
K W
KW
Hsu
W H
WH
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D012417:Rumen / Q000187:drug effects; D014991:Xylazine / Q000008:administration & dosage / Q000037:antagonists & inhibitors*
D000317:Adrenergic alpha-Antagonists; D006993:Hypnotics and Sedatives; D007093:Imidazoles; C050701:atipamezole; D014991:Xylazine