Effects of buprenorphine, butorphanol or tramadol premedication on anaesthetic induction with alfaxalone in common marmosets (Callithrix jacchus)

To investigate the clinical and physiological effects of intravenous (IV) alfaxalone alone or in combination with buprenorphine, butorphanol or tramadol premedication in marmosets. Prospective, randomized, blinded, crossover design. Nine healthy marmosets (391 ± 48 g, 3.7 ± 2.2 years old). Meloxicam 0.20 mg kg−1 subcutaneously, atropine 0.05 mg kg−1 intramuscularly (IM) and either buprenorphine 20 μg kg−1 IM (BUP-A), butorphanol 0.2 mg kg−1 IM (BUT-A), tramadol 1.5 mg kg−1 IM (TRA-A) or no additional drug (control) were administered to all marmosets as premedication. After 1 hour, anaesthesia was induced with 16 mg kg−1 alfaxalone IV. All animals received all protocols. The order of protocol allocation was randomized with a minimum 28 day wash-out period. During anaesthesia, respiratory and pulse rates, rectal temperature, haemoglobin oxygen saturation, arterial blood pressure, palpebral and pedal withdrawal reflexes and degree of muscle relaxation were assessed and recorded every 5 minutes. Quality of induction and recovery were assessed. Duration of induction, immobilization and recovery were recorded. Blood samples were analysed for aspartate aminotransferase, creatine kinase and lactate dehydrogenase concentrations. The protocols were compared using paired t tests, Wilcoxon's signed-rank test with Bonferroni's corrections and linear mixed effect models where appropriate. Out of nine animals, apnoea was noted in eight animals administered protocol BUP-A and two animals administered protocol BUT-A. With TRA-A and control protocols, apnoea was not observed. No other significant differences in any of the parameters were found; however, low arterial blood pressures and hypoxia occurred in TRA-A. Our study employing different premedications suggests that the previously published dose of 16 mg kg−1 alfaxalone is too high when used with premedication because we found a high incidence of complications including apnoea (BUP-A), hypotension and hypoxaemia (TRA-A). Appropriate monitoring and countermeasures are recommended.