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Objective

To evaluate the antagonistic effects of yohimbine on sedation induced in dogs with medetomidine.

Methods

Mixed breed dogs of both sexes were randomly assigned to one of two groups of six. The dogs in group 1 (M) received 40 μg/kg of medetomidine followed 15 minutes later by 0.2 ml/ kg saline solution. The dogs in group 2 (MY) received the same doses of medetomidine, followed 15 minutes later by 0.11 mg/kg yohimbine. All the dogs were examined before and five, 15, 30, 45, 60, 75, 90, 120 and 150 minutes after the injection of medetomidine. In both groups, the induction and recovery times, vital signs, blood biochemical values and scores of anesthetic effects were determined.

Results

The MY group had a higher mean heart rate at 15 and 30 minutes than the M group. The MY group had a higher mean respiratory rate at 15 and 30 minutes than the M group. The MY group had a significantly higher mean temperature at 15 and 30 minutes than the M group. After the administration of yohimbine, the glucose concentration of MY group was lower than that of the M group. The total protein concentration of the MY dogs was lower than those of M dogs after 45, 75 and 180 minutes. The activity of ALT and AST did not change significantly in either group and there was no significant difference between them at any time. When recovering from anesthesia, the dogs treated with yohimbine took significantly less time to achieve sternal recumbency (mean [sd] 17 [1.14] v 44.4 [7.27] minutes), and less time to be able to stand (mean [SD] 24.0 [4.18] v 72.2 [9.55] minutes), and walk (mean [SD] 25.6 [4.22] v 82.2 [10.36]). After the administration of yohimbine, the score of anesthetic effects in the MY group was significantly lower than that of the M group.

Conclusion

The administration of yohimbine effectively reversed medetomidine sedation in dogs. It caused changes in the vital signs and blood biochemistry but within the normal range.