ABSTRACT
The antagonistic effect of the alpha 2-adrenoceptor antagonists atipamezole and yohimbine on medetomidine-induced sedation was studied in male Awassi sheep. The animals were sedated with an im injection of 40 micrograms medetomidine/kg bw. After recumbency, the sheep were injected iv with either 5 ml physiological saline solution (control), 0.2 mg atipamezole/kg or 0.2 mg yohimbine/kg. The saline-treated animals remained sedated and recumbent for 61.3 +/- 3.0 (mean +/- SE) min. Atipamezole or yohimbine significantly reduced the recumbency period to 2.8 +/- 0.9 or 4.3 +/- 0.9 min, respectively. Atipamezole or yohimbine significantly increased the medetomidine-induced reductions in the heart rate, respiratory rate and ruminal contractions. Rectal temperature was neither affected by medetomidine nor by the subsequent administrations of antagonists. These data suggest the usefulness of atipamezole or yohimbine in antagonizing the sedative effects of medetomidine in sheep.
Subject(s)
Hypnotics and Sedatives/antagonists & inhibitors , Imidazoles/antagonists & inhibitors , Imidazoles/pharmacology , Yohimbine/pharmacology , Adrenergic alpha-Antagonists/pharmacology , Animals , Drug Interactions , Hypnotics and Sedatives/pharmacology , Male , Medetomidine , SheepABSTRACT
The sedative effect of medetomidine was evaluated in 6 male Awassi sheep. Medetomidine at 40 micrograms/kg, i.m. induced sedation and recumbency in the sheep within 9 +/- 1 and 17 +/- 4 minutes, respectively. The duration of recumbency was 58 +/- 1 minutes. Medetomidine produced good analgesia and marked muscle relaxation in the recumbent animals for 30 to 45 minutes. The side effects of medetomidine were bradycardia, respiratory depression, stasis of the rumen with tympany, salivation and polyuria. The animals recovered from the sedative and side effects of medetomidine 1.5 to 2 hours after gaining the righting reflex without any apparent adverse effect. The results suggested that medetomidine could be a useful sedative analgesic in sheep.
