Sedative effects of medetomidine in pigs

Sedative effects of medetomidine, a potent selective and specific alpha 2-adrenoceptor agonist, were evaluated in pigs using 5 different doses (30, 50, 80, 100 and 150 micrograms/kg of body weight) and compared with those of xylazine (2 mg/kg). Atropine (25 micrograms/kg) was mixed with both drugs to prevent severe bradycardia. All drugs were administered intramuscularly. Medetomidine at a dosage of 30 micrograms/kg produced more potent sedation than xylazine. The depth of sedation induced by medetomidine was dose dependent within the range from 30 to 80 micrograms/kg. At 100 or 150 micrograms/kg, the depth of sedation was mostly the similar level to that at 80 micrograms/kg but the duration was prolonged. The degree of muscle relaxation produced by medetomidine also seemed to be dose dependent from 30 to 80 micrograms/kg and was stronger than that produced by xylazine. An increase in the duration of muscle relaxation was dose dependent up to 150 micrograms/kg. No analgesic effect was produced by xylazine, however moderate analgesia was obtained by medetomidine. There were no marked changes in heart rate and respiratory rate during the observation period in pigs of any groups, however mild hypothermia after the administration of both drugs was observed. From these results, medetomidine has a significant and dose-dependent sedative effects which are much more potent than that of xylazine, and a combination of 80 micrograms/kg of medetomidine and 25 micrograms/kg of atropine is suitable for sedation with lateral recumbency and moderate muscle relaxation without notable side effects in pigs.