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Table 2 Summary of the properties of injectable anaesthetics

From: Anaesthesia and physiological monitoring during in vivo imaging of laboratory rodents: considerations on experimental outcomes and animal welfare

Anaesthetic agent Advantages Disadvantages Dosing
Fentanyl/fluanisone (Hypnorm™)-based combination Good analgesic effect Cardiovascular and respiratory depression 10 ml/kg (mouse), 2.7 ml/kg (rat) i.p. mixture Hypnorm™/Hypnovel™ (midazolam)/water mixture (1:1:2 volume) (120 to 140 min sleep time)Hypnorm™ top-up 0.3 ml/kg (mouse), 0.1ml/kg (rat) i.p. (30 to 40 min sleep time)
  Sedative Poor muscle relaxation alone  
  Possible to top-up for long-term anaesthesia Risk of enterohepatic recirculation: relapse  
  Reversal of sedative effect with buprenorphine to speeds up recovery time Prolonged recovery time  
   Hypersensitivity to noise  
Ketamine-based combination Analgesic effects Muscle rigidity +++ unless combined with other agents. Ketamine + medetomidine 75 mg/kg + 0.5 to 1 mg/kg i.p.(Ketamine + xylazine 75 to 100 mg/kg)/(10mg/kg i.p.)(60 to 120 min sleep time ) (mouse and rats)Atipamezole 1mg/kg i.p.
  Light sedation Increases intracranial pressure.  
  Wide safety margin Recovery often involved with ataxia and hyper responsiveness.  
   Can increase blood pressure  
Alfaxalone (Alfaxan) Minimal respiratory or CVS depression Administration route i.v. (rodents, cats) or i.m. (primates) 15 to 20mg/kg (mouse), 10 to 12mg/kg (rat) i.v.(10 to 15 min sleep time after bolus)0.25 to 0.75 mg/kg/min i.v. infusion (long term)
  Rapidly metabolised, repeated doses do not accumulate.   
  Suitable for long-term anaesthesia in rodents   
Propofol (Rapinovet®, Diprivan®) Rapidly metabolised, continuous infusion possible for long-term anaesthesia. i.v. use only 26 mg/kg (mouse), 10 to 12mg/kg (rat) i.v.(10 to 15 min sleep time after bolus)2 to 2.5 mg/kg/min i.v. infusion (long-term, mouse) 0.5 to 1 mg/kg/min i.v. infusion (long-term, rat)
   No analgesic properties  
  Rapid recovery Severe respiratory depression  
  Can be used in animals with hepatic or renal impairment. Apnoea can occur after i.v. bolus  
Barbiturates products Sedative effect No analgesic properties Pentobarbitone, 40 to 50mg/kg i.p. (mouse) (120 to 180 min sleep)
  Good hypnotic effect Severe respiratory depression and hypotensive  
  Reasonable muscle relaxation Easy to overdose Thiopentone, 30 mg/kg i.v. 15 min sleep (rat)
   Metabolites accumulate with time  
   Caustic substances (thiopentone only i.v. route)  
Chloral hydrate Sedative effect No analgesic properties 300 to 400 mg/kg i.p. (1 to 2 h sleep time) (mouse and rats)
  Good hypnotic effect Paralytic ileus noted in rats  
  Minimal CVS and respiratory depression Terminal/non-recovery work only  
α-Chloralose Sedative effect No analgesic properties 50 to 60 mg/kg i.p. (rats), 120 mg/kg i.p. (mouse)(8 to 12 h for non-recovery only)50 mg/kg i.v. bolus followed by 25 to 40 mg/kg/h (rats)
  Good hypnotic effect i.v. use only  
  Suitable for long-term anaesthesia Slow induction and recovery associated with involuntary excitement  
  Minimal CVS and respiratory depression Terminal/non-recovery work only  
Urethane Suitable for long-term anaesthesia. Carcinogenic: only allowed to be used with special justification 0.8 to 1.3 g/kg i.p. (mouse and rats)Duration of action 8 to 10 h (non-recovery only)
  Minimal CVS and respiratory depression Terminal/non-recovery work only  
Avertin® (tribromoethanol) Wide safety margin Local irritation/peritonitis 0.015 ml/g body wt of 2.5% i.p.
  Good muscle relaxation Handling and storage safety issues 30 min; supplemental doses of anaesthesia: minimum of 1/2 of the initial dose up to 1 ml maximum volume per animal
  Rapid induction and recovery Toxic effects