Comparison of three different sedative-anaesthetic protocols (ketamine, ketamine-medetomidine and alphaxalone) in common marmosets (Callithrix jacchus)
Summary
Objective To compare the clinical use of three different sedatives (ketamine, ketamine-medetomidine and alphaxalone) in common marmosets for a short-acting, safe and reliable sedation protocol.
Study design Double blind randomized crossover study.
Animals Ten (5 male and 5 female) healthy adult common marmosets (Callithrix jacchus) of various ages (range 2,10-6.85 years) and body weights (312-401 grams).
Methods The design of the crossover study was: 10 marmosets were randomly assigned, to receive each of the three sedation regimens in random order on 3 different occasions (days 28, 56 and 84). The three regimens included: protocol 1: 50 mg/kg ketamine i.m., protocol 2: 12 mg/kg alphaxalone i.m. and protocol 3A: 25 mg/kg ketamine and 0,5 mg/kg medetomidine i.m., reversed with 2,5 mg/kg atipamezole i.m Following completion and unblinding, the project was extended with an additional protocol (3B), because 3A led to unacceptably long recovery times. Protocol 3B comprised of 25 mg/kg ketamine combined with 0.05 mg/kg medetomidine (reversal with 0.25 mg/kg atipamezole, twice with 35 min interval).
Results All protocols in this study provided rapid onset (induction times <5 min) of immobilisation and sedation. Duration of immobilisation was 31.23 ± 22.39 min, 53.72 ± 13.08 min, 19.73 ± 5.74 min, and 22.78 ± 22.37 min for protocol 1, 2, 3A, and 3B, respectively. Recovery times were 135.84 ± 39.19 min, 55.79 ± 11.02 min, 405.46 ± 29.81 min, and 291.91 ± 80.34 min, respectively. Regarding the quality, and reliability (judged by pedal withdrawal reflex, palpebral reflex and muscle tension) of all protocols, protocol 2 was the most optimal. Monitored vital parameters were within clinically acceptable limits during all protocols and there were no fatalities. Indication of muscle damage as assessed by AST, LDH and CK values was most prominent elevated in protocol 1, 3A, and 3B.
Conclusion We conclude that intramuscular administration of 12 mg/kg alphaxalone to common marmosets is preferred over other protocols studied. Protocol 2 resulted in at least comparable immobilisation quality with acceptable and less frequent side effects and superior recovery quality. In all protocols, supportive therapy, such as external heat support, remains mandatory. Notably, an unacceptable long recovery period in both ketamine/medetomidine protocols (subsequently reversed with atipamezole) was observed, showing that α-2 adrenoreceptor agonists in the used dose and dosing regime is not the first choice for sedation in common marmosets in a standard research setting.