Comparative Evaluation of the Sedative and Analgesic Effects of Caudal Epidural Administration of Lidocaine Alone or in Combination With Xylazine, Detomidine, Medetomidine, and Dexmedetomidine in Mediterranean Miniature Donkeys

The present study aimed to compare the sedative and analgesic effects of caudal epidural administration of lidocaine alone or in combination with four different α₂-adrenergic agonists in Mediterranean miniature donkeys. A total of ten clinically healthy (five males and five females) Mediterranean miniature donkeys with an age of 5 ± 1 years, a weight of 100 ± 2 kg and a height at the withers of 0.8 ± 0.06 m (mean ± standard deviation) were used in experimental, crossover (Latin square), randomized, and blinded study. Animals were assigned to five treatment groups including lidocaine alone (0.22 mg kg^-1), or associated with one among xylazine (0.17 mg kg^-1), detomidine (30 μg kg^-1), medetomidine (15 μg kg^-1), dexmedetomidine (5 μg kg^-1) with a minimum washout period of 8 days between treatments. The degree of sedation was investigated using a simple descriptive scale of 0-3. Sedation scores were compared at each time using nonparametric (Kruskal-Wallis and Mann-Whitney U) tests. Analgesia was assessed by pinprick test. Sedation was greater in lidocaine and/or α₂-adrenergic agonist groups than in lidocaine group at 45-75 minutes after drug administration (P < .05). There were no significant differences among groups in time to onset of analgesia and ataxia and also in number of animals with complete perineal analgesia and ataxia. Duration of analgesia and ataxia were longer in lidocaine and/or α₂-adrenergic agonist groups than in lidocaine (P < .05). There were no significant differences among lidocaine and/or α₂-adrenergic agonist groups in sedation score and duration of analgesia and ataxia. No significant differences were observed in heart and respiratory rate and also rectal temperature at any time points between groups and within groups. Caudal epidural administration of α₂- adrenergic agonists associated with lidocaine resulted in sedative effects on Mediterranean miniature donkeys, while lidocaine alone did not induce sedation. These drugs associations should be considered when superior analgesia is advocated.