Antinociceptive activity and mechanism of action of detomidine

The antinociceptive activity and mechanism of action of detomidine, a novel sedative-analgesic, were studied in mice and rats. Xylazine and morphine were included in the studies for comparison. In both acetic acid-induced writhing test in mice, and in tail flick test in rats, detomidine had potent, dose-dependent antinociceptive effects with ED50 values of 0.06 and 0.2 mg/kg i.p., respectively. Both xylazine and morphine were clearly less potent than detomidine in these tests. The antinociceptive effect of detomidine was only inhibited by alpha-2 antagonists (idazoxan, rauwolscine), which suggests that this action is mediated through stimulation of alpha-2 adrenoceptors. The significance of these findings for the use of detomidine in veterinary medicine is discussed.