Intramuscular administration of alfaxalone for sedation in rabbits.

Alfaxalone is a neuroactive steroid derivative of pregnanedione that was recently reintroduced to the market for use as an induction agent in small animal anaesthesia. The aim of this study was to determine an intramuscular alfaxalone dose for safe immobilisation. Ten healthy New Zealand white rabbits were used to evaluate a single intramuscular injection of alfaxalone. The design of the study was a three-way, complete block, cross-over trial to compare the effect of alfaxalone at three doses (4, 6 and 8 mg). The mean duration of the effect for the 4, 6 and 8 mg/kg doses was, respectively, 36.9 (95% CI (31.6 to 42.3)), 51.8 (46.4 to 57.2) and 58.4 (52.8 to 63.9) minutes. The loss of the righting reflex was achieved after 3.1 (2.5 to 3.8), 2.4 (1.7 to 3.1) and 2.3 (1.6 to 2.9) minutes, respectively. The mean duration of the effect for the 6 and 8 mg doses was significantly higher than for the 4 mg dose (with estimated differences of 14.8 95% CI (8.8 to 20.8) minutes and 21.4 (15.3 to 27.6) minutes, respectively). No significant dose effect was observed before the loss of the righting reflex (P=0.14). Ear pinching and limb withdrawal were elicited in all groups at every dose. Doses of 4 or 6 mg/kg could be recommended; higher doses do not provide clinical benefits and can be associated with anaesthetic complication.