Antagonistic effect of atipamezole, flumazenil and naloxone following anaesthesia with xylazine, tramadol and tiletamine/zolazepam combinations in pigs.

Objective: To evaluate the antagonistic effects of atipamezole (ATI), flumazenil (FLU) and naloxone (NAL) alone and in various combinations following administration of tiletamine-zolazepam-xylazine-tramadol.

Study Design: Prospective, experimental, randomized cross-over study.

Animals: Eight Chinese miniature pigs (three females and five males) mean age 8 (range 7-10) months and bodyweight 57.5 (52.4-62.1) kg.

Methods: All animals were anaesthetized with tiletamine/zolazepam (3.0 mg kg(-1)), xylazine (1.2 mg kg(-1)) and tramadol (1.6 mg kg(-1)) given intramuscularly (IM). Thirty minutes later, one of eight treatments was administered IM: saline control, ATI (0.12 mg kg(-1)), FLU (0.1 mg kg(-1)), NAL (0.03 mg kg(-1)), ATI-FLU, FLU-NAL, ATI-NAL or ATI-FLU-NAL. After injection of antagonists the following times were recorded: to recovery of the palpebral, pedal and tail clamp reflexes, to head movement, sternal recumbency, standing and walking. Posture, sedation, analgesia, jaw relaxation and auditory response were scored at set times until 120 minutes after injection of antagonists. Heart rates, respiratory rates and rectal temperature were measured at those times. Data were analyzed by anova for repeated measures, followed by the Tukey's test to compare differences between means, or by Kruskal-Wallis test as appropriate.

Results: FLU, NAL alone, or FLU-NAL did not effectively antagonize anaesthesia induced by tiletamine/zolazepam-xylazine-tramadol. ATI, ATI-FLU, ATI-NAL and ATI-FLU-NAL produced an immediate and effective recovery from anaesthesia. The combination of ATI-FLU-NAL was the most effective combination in antagonizing the anaesthetic effect. Adverse effects such as tachycardia, tachypnoea, excitement and muscle tremors were not observed during this study.

Conclusion And Clinical Relevance: ATI-FLU-NAL is the most effective combination for antagonizing tiletamine/zolazepam-xylazine-tramadol anaesthesia in pigs. However, ATI alone or in various combinations also provides effective antagonism.