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Intravenous (IV) administration in mice is predominantly performed via the lateral tail veins. The technique requires adequate training before it can be used safely and routinely. A novel anaesthesia induction chamber has been developed to simplify the treatment and to facilitate IV injection in mice, particularly for untrained personnel. We have assessed the benefits of the chamber in refining IV injection in isoflurane-anaesthetized mice in direct comparison with the common restrainer method on conscious animals. The body weight, nesting behaviour and concentrations of faecal corticosterone metabolites were taken as indicative of distress induced by the various procedures. The results suggest that both methods of tail-vein injection induce similar levels of momentary stress in the animals, revealed by a short-term increase in the levels of stress hormone metabolites in faeces. A temporary reduction of body weight was observed after IV injection under isoflurane anaesthesia but not for conscious mice injected in the common restrainer. We conclude that the severity of tail-vein injection in mice is 'mild' for both methods. There was no evidence that refining the procedure by using isoflurane anaesthesia in the induction chamber was associated with any benefit. [ABSTRACT FROM AUTHOR]