In a double blind study, eight horses were treated intravenously at seven-day intervals with detomidine at doses of 10, 20 and 40 micrograms/kg, or with romifidine at doses of 40, 80 and 120 micrograms/kg, or with a placebo solution. Their sedative and analgesic effects were evaluated by objective measurements and by a clinician at 15-minute intervals for three hours and the horses' instability in stocks, locomotor ataxia and heart rate were recorded simultaneously. The administration of both drugs at all doses resulted in sedation. The sedation achieved with romifidine was significantly shallower and shorter-lived than with detomidine at the recommended doses (P < 0.05). The results obtained with the highest dose of romifidine were in some cases significantly inferior and shorter-lived than those obtained with the medium dose (P < 0.05). Detomidine at the 10 micrograms/kg dose was similar in its effects to the two highest doses of romifidine. At all doses detomidine had analgesic properties against the effects of electrical pain stimulation at the withers, the coronary bands on the front and hind legs, and in the perianal region, which were dose-dependent in depth and duration, whereas romifidine was devoid of any analgesic effect. Instability and ataxia were more pronounced with detomidine than with romifidine but the effects were only slight to moderate and not regarded as a hindrance to procedures for which sedation is needed. Bradycardia was evident with both drugs at all doses; its severity and duration was related to the sedative properties of the drugs and was dose related. No other side effects were observed.

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Summary Detomidine hydrochloride, butorphanol tartrate, flunixin meglumine and xylazine hydrochloride were evaluated in a blind multi‐centre clinical trial in 152 horses with abdominal pain. The drugs were administered as follows: detomidine 20 or 40 μg/kg bodyweight (bwt); butorphanol 0.1 mg/kg bwt; flunixin meglumine 1.0 mg/kg bwt; xylazine hydrochloride 0.5 mg/kg bwt. Each centre compared responses to the two doses of detomidine with those to one of the other analgesics. The drugs were administered intravenously (iv) after clinical assessment of the degree of sweating, kicking, pawing, head and body movement, attitude, lip curling, stretching to urinate, pulse rate, respiratory rate and rectal temperature. Similar assessments were repeated at 15 min intervals for at least 1 h. The investigators ranked the response to treatment from ‘not satisfactory’ to ‘highly satisfactory’. Significant differences in sweating, kicking, pawing, head and body movement, attitude, pulse rate and respiratory rate were noted between the horses receiving butorphanol and either dose of detomidine. The investigators' subjective evaluation of the analgesic and sedative effects of either dose of detomidine were significantly better than for butorphanol. Analgesia was rated as highly satisfactory or satisfactory in 93.3 per cent and 6.7 per cent of the horses receiving 40 μg/kg bwt of detomidine, 73.3 per cent and 26.7 per cent of the horses receiving 20 μg/kg bwt of detomidine, and none of the horses receiving butorphanol. There were no differences in the incidence of side effects with the two compounds. Significant differences were noted in kicking, pawing, head and body movement and attitude between the horses receiving flunixin meglumine and either dose of detomidine. Flunixin meglumine provided significantly less analgesia than either dose of detomidine. Analgesia was rated as highly satisfactory or satisfactory in 73.7 per cent and 21.0 per cent of the horses receiving 40 μg/kg bwt of detomidine, 42.9 per cent and 21.4 per cent of the horses receiving 20 μg/kg bwt of detomidine, and 6.3 per cent and 37.5 per cent of the horses receiving xylazine. Sedation was considered to be at least satisfactory in 84.2 per cent of the horses receiving 40 μg/kg of detomidine, 71.5 per cent of the horses receiving 20 μg/kg of detomidine and 53.3 per cent of the horses receiving xylazine.