This study was performed to clarify the antagonistic actions of intravenous or epidural atipamezole on the sedative and analgesic effects of xylazine administered between the epidural fat and dura mater through the first interlurnbar space in cattle.
Cattle received 5 mL of a solution containing 0.05 mg kg(-1) xylazine in 0.9% saline. Thirty minutes later, 5 mL of 0.9% saline was administered through the same needle (treatment 1) (XSE). In treatments 2 (XAE) and 3 (XAV), 5 mL of a solution containing 0.025 mgkg(-1) atipamezole in 0.9% saline was administered epidurally or intravenously, respectively.
Sedation,and analgesia were similar in all three treatment groups and could be reversed by atipamezole given by either route. In the XAV treatment, the flank area relapsed into analgesia 25 +/- 5.8 min following reversal of the analgesic effect, and was maintained for 112.5 +/- 63.8 min.
The present study confirmed that the sedative and analgesic effects of xylazine are completely reversed by atipamezole and can be influenced by the epidural fat in cattle. Furthermore, it seems probable that analgesia following epidural administration of xylazine is mediated by alpha(2)-adrenergic receptors, not by a local anaesthetic effect. (C) 2003 Elsevier Science Ltd. All rights reserved.