POSSIBLE INVOLVEMENT OF EPINEPHRINE IN THE CARDIOVASCULAR EFFECT OF NALOXONE IN HUMANS

Abstract

The opioid-receptor antagonist naloxone was administered i.v. in a 0.8-mg bolus to 5 healthy volunteers, aged 21 to 31, in a double-blind study designed to investigate the effect of endogenous opioids on blood pressure, heart rate, and urinary excretion of catecholamines in healthy adults. Three h after administration of naloxone there were significant increases in systolic blood pressure (P < 0.001) and heart rate (P < 0.05). The amount of epinephrine excreted in urine during the 4 h after administration of naloxone or placebo was significantly higher (P < 0.05) in subjects given naloxone. These effects support the hypothesis that an endogenous opioid system is involved in the regulation of systolic blood pressure and heart rate in healthy adults. Adrenally released epinephrine could mediate the cardiovascular effect of endogenous opioids.