Table 2 Summary of the properties of injectable anaesthetics

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