Cardiovascular, respiratory, thermoregulatory, sedative, and analgesic effects of intravenous administration of medetomidine in rhesus macaques (Macaca mulatta)

Background and Purpose: Medetomidine is a selective, specific, and potent a lpha 2-adrenergic receptor agonist that has been utilized successfully as a sedative/analgesic agent in a variety of domestic and nondomestic animals. The objective of this study was to document the physiological effects of t he intravenous administration of medetomidine in rhesus macaques (Macaca mu latta). Methods: Fifteen healthy rhesus macaques (Macaca mulatta), 5 to 15 years ol d and weighing 5.5 to 11.8 kg, were gives four dosages of medetomidine (50, 100, 150, and 200 mu g/kg of body weight) intravenously, and cardiovascula r, respiratory, thermoregulatory, sedative, and analgesic effects were dete rmined. Results: All four doses of medetomidine induced a similar and significant d ecrease in mean arterial pressure, as well as a transient but significant i ncrease in respiratory rate followed by a longer-lasting significant decrea se. Bradycardia, hypotension, and loss of thermoregulatory ability accompan ied by a biphasic respiratory response and inconsistent sedation, analgesia , and muscular relaxation were observed. Heart rate decrease was rapid for all doses, but was significantly lower and of shorter duration after admini stration of the 50 mu g/kg dosage. Conclusion: The inconsistency of the anesthetic plane induced by intravenou s administration of medetomidine precludes it from being used alone to seda te rhesus macaques.