Effects of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, on hemodynamic control mechanisms.

Dexmedetomidine, a selective alpha 2-adrenoceptor agonist, was administered to five healthy male volunteers in single intravenous doses of 12.5, 25, 50, and 75 micrograms as part of a placebo-controlled study. The drug caused dose-dependent decreases in systolic and diastolic blood pressure. A small initial hypertensive response was observed after injection of the two highest doses. Heart rate was decreased. The concentration of norepinephrine in plasma was decreased significantly (by up to 92%), and the decrease was dose-dependent. No significant drug-induced alterations were observed in plasma renin activity or in the concentrations of atrial natriuretic peptide and arginine vasopressin in plasma. Other drug effects included dose-dependent impairment of vigilance and stimulation of growth hormone secretion. Plasma cortisol levels were unaffected. Dexmedetomidine is a potentially useful tool for studies of the physiology and pharmacology of alpha 2-adrenoceptors in human beings and may have therapeutic applications in clinical conditions in which sedative and sympatholytic effects are considered beneficial, such as premedication for anesthesia and surgery.