Romifidine, 100 micrograms/kg administered by intravenous injection, was evaluated as a premedicant to ketamine/halothane anaesthesia in 60 horses. Sedation developed within one to two minutes. In three cases mild staggering occurred within two minutes. Anaesthesia was induced after five minutes by the intravenous administration of ketamine (2 to 2.2 mg/kg). A mean time of 79 seconds elapsed before lateral recumbency was adopted. Fifty-four of the horses sank smoothly to the floor, with occasional steps sideways. Jaw tone, limb rigidity and mild muscle tremors often persisted for short periods after induction. Complete relaxation was achieved on average two minutes after the administration of ketamine. The transition to oxygen/halothane anaesthesia was excellent or good in 53 cases. The mean duration of anaesthesia was 79 minutes. Forty-seven of the horses were able to stand after one or two attempts with little or no ataxia. After halothane administration ceased, the mean time to sternal recumbency was 25 minutes and the mean time to standing was 33 minutes. Most horses appeared to be sedated upon standing, but they were able to walk soon after regaining their feet. The characteristics of the induction of anaesthesia were similar to those seen when detomidine/ketamine or xylazine/ketamine are used. The maintenance of anaesthesia with halothane was similar to that following other induction protocols, and the recovery from anaesthesia was smooth and free from excitement.
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