Comparison of detomidine, butorphanol, flunixin meglumine and xylazine in clinical cases of equine colic

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 micrograms/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 (i.v.) 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 micrograms/kg bwt of detomidine, 73.3 per cent and 26.7 per cent of the horses receiving 20 micrograms/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 micrograms/kg bwt of detomidine, 42.9 per cent and 21.4 per cent of the horses receiving 20 micrograms/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 micrograms/kg of detomidine, 71.5 per cent of the horses receiving 20 micrograms/kg of detomidine and 53.3 per cent of the horses receiving xylazine.