Combined use of sedatives and opiates in horses

The effects of four intravenous combinations, xylazine (0.7 mg/kg)/methadone (0.1 mg/kg), xylazine (0.7 mg/kg)/buprenorphine (0.004 and 0.006 mg/kg) and acepromazine (0.05 mg/kg)/buprenorphine (0.006 mg/kg) on arterial blood pressure, central venous pressure, heart rate, respiratory rate and blood gases were studied in four experimental ponies. With xylazine/buprenorphine and xylazine/methadone onset of sedation was rapid and obvious and although no surgical or diagnostic procedures were carried out, sedation was judged to be satisfactory for the next 30 to 40 minutes. Onset of sedation after intravenous injection of acepromazine/buprenorphine was slower and less obvious, while its duration was difficult to determine for the ponies could be aroused by noise even when apparently fully sedated. The observations indicated that at the stated doses all the drug combinations should be safe for clinical use.