title: Antagonistic effect of idazoxan on xylazine-induced central nervous system depression and bradycardia in calves.
abstract: Two doses of an alpha 2-adrenoreceptor antagonist, idazoxan, were administered to reverse the CNS depressant and bradycardia effects of xylazine in calves. Once a week for 3 weeks, each of 6 calves were administered IV one treatment of: (1) 0.2 mg of xylazine/kg of body weight followed in 10 minutes by 1 ml of 0.9% NaCl, (2) 0.2 mg of xylazine/kg followed in 10 minutes by 10 micrograms of idazoxan/kg, or (3) 0.2 mg of xylazine/kg followed in 10 minutes by 30 micrograms of idazoxan/kg. The order of the 3 treatments in each calf was selected at random. Xylazine alone caused lateral recumbency for 27.2 +/- 3.0 minutes (mean +/- SEM). Idazoxan administered at dosages of 10 and 30 micrograms/kg shortened xylazine-induced lateral recumbency to 11.5 +/- 0.8 and 10.3 +/- 0.2 minutes, respectively. Calves given xylazine alone stood at greater than 60 minutes after the onset of recumbency. Idazoxan given at dosages of 10 and 30 micrograms/kg shortened the time to standing to 16.8 +/- 1.7 and 11.3 +/- 0.2 minutes, respectively. Idazoxan given at a dosage of 30 micrograms/kg also reversed xylazine-induced bradycardia. Results indicated that idazoxan should be a useful antidote for xylazine overdose in cattle.
authors.affiliation: Department of Veterinary Clinical Sciences, Iowa State University, Ames 50011.
authors.forename: J R
authors.initials: JR
authors.lastname: Thompson
authors.forename: W H
authors.initials: WH
authors.lastname: Hsu
authors.forename: K W
authors.initials: KW
authors.lastname: Kersting
mesh_terms: D000818:Animals; D001919:Bradycardia / Q000139:chemically induced / Q000188:drug therapy / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000139:chemically induced* / Q000188:drug therapy; D002490:Central Nervous System / Q000187:drug effects* / Q000502:physiology; D004146:Dioxanes / Q000494:pharmacology* / Q000627:therapeutic use; D004147:Dioxins / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D019329:Idazoxan; D008297:Male; D013843:Thiazines / Q000037:antagonists & inhibitors*; D013997:Time Factors; D014991:Xylazine / Q000009:adverse effects / Q000037:antagonists & inhibitors*
chemical_list: D004146:Dioxanes; D004147:Dioxins; D013843:Thiazines; D014991:Xylazine; D019329:Idazoxan