Potentiating the Epidural Analgesic Effect of Lidocaine in Uda Sheep with Xylazine and Medetomidine

This study was undertaken to compare the analgesic effects of lidocaine, xylazine, and medetomidine alone and their combinations with lidocaine in Uda sheep. The sheep (n = 6) were assigned to five different epidural treatment groups using a cross-over design with a wash-out period of one week between the treatment groups. The group (A) received lidocaine at 2.86 mg/kg, the group (B) received xylazine at 0.05 mg/kg, the group (C) received medetomidine at 20 µg/kg, the group (D) received lidocaine-xylazine combination at 2.15 mg/kg and 0.125 mg/kg, respectively, and the group (E) received lidocaine-medetomidine combination at 2.15 mg/kg and 5 µg/kg, respectively. The analgesic effect was evaluated by the needle-prick test method. The onset and duration of analgesia in the mentioned regions were recorded. Ataxic and sedative effects were carefully observed and recorded according to the scoring system. Blood was collected at baseline (0), immediately after onset, and 24 hours post-administration. Results showed that medetomidine treatment produced a highly significant (p < 0.01) earlier onset of action (6–8 min) than the rest of the treatment groups. Medetomidine treatment also produced a significantly (p < 0.001) longer duration of analgesia (190-230 min) than the rest of the treatment groups. Lidocaine alone or in combination with xylazine or medetomidine induced severe ataxia, while xylazine and medetomidine alone or in combination with lidocaine produced mild to moderate sedation. In conclusion, epidural administration of medetomidine, lidocaine-xylazine, and xylazine produced a prolonged, longer duration of analgesia with useful systemic sedation in sheep.