EPIDURAL VERSUS SYSTEMIC ADMINISTRATION OF ALPHA 2 AGONISTS IN SHEEP

摘要

Xylazine and detomidine are commonly used alpha 2 adrenoceptor agonists in ruminants. The aim of the study was to compare the sedative and analgesic properties of xylazine and detomidine when administered IM and epidurally (EPI). Six, healthy sheep (1-3 years) and weighing 20 - 45 kg were used in the study. Each sheep was studied on 4 occasions, at weekly intervals, and each received all of the treatments. The following treatments were administered: Group 1 (xylazine, 0,3 mg/kg, IM), Group 2 (xylazine, 0.3 mg/kg, EPI), Group 3 (detomidine, 20 mug/kg, IM) and Group 4 (detomidine, 20 mug/kg, EPI). Sedative and analgesic effects of both drugs were recorded. Analgesia was determined by the response to a needle prick. Pulse rate, respiratory rate, rectaltemperature and ruminanl motility were recorded at 15 minutes intervals following drug administration and continued until recovery. Blood was collected for hematological and biochemical analysis at the same time intervals. Descriptive statistical analysis was performed. Sedation was evident in all treated sheep. Analgesia occurred within two minutes with no significant difference in its time of onset among the four groups. Duration of analgesia was longer following EPI xylazine (108 ± 17 minutes) thanthat following IM xylazine, IM detomidine, and EPI detomidine (37 ± 7, 36 ± 5.7 and 33 ± 8.3, respectively). Analgesia of the tail, perineum, hind limbs, flank, thoracic wall and fore limbs was moderate following IM xylazine, but mild after IM detomidine. Following EPI xylazine, analgesia of the tail, perineum, hind limbs and flank was complete, but after EPI detomidine, it was mild to moderate. Ataxia was evident following IM administration of either drugs, but was marked following their EPI administration, especially in the case of xylazine, which produced recumbency on all occasions. Changes in the clinical, hematological, and biochemical parameters were transient and returned to the pre-injection values at the end of the experiment. Based on these findings, epidural administration of xylazine to sheep produces a greater degree of analgesia for the tail, perineum, hind limbs and flank region than similar doses administered IM.