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 alpha2-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 the intravenous administration of medetomidine in rhesus macaques (Macaca mulatta).

Methods: Fifteen healthy rhesus macaques (Macaca mulatta), 5 to 15 years old and weighing 5.5 to 11.8 kg, were given four dosages of medetomidine (50, 100, 150, and 200 microg/kg of body weight) intravenously, and cardiovascular, respiratory, thermoregulatory, sedative, and analgesic effects were determined.

Results: All four doses of medetomidine induced a similar and significant decrease in mean arterial pressure, as well as a transient but significant increase in respiratory rate followed by a longer-lasting significant decrease. Bradycardia, hypotension, and loss of thermoregulatory ability accompanied 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 administration of the 50 microg/kg dosage.

Conclusion: The inconsistency of the anesthetic plane induced by intravenous administration of medetomidine precludes it from being used alone to sedate rhesus macaques.