Metabolic and calorigenic effects of dopexamine in healthy volunteers

Objective: To evaluate metabolic and calorigenic effects of dopexamine in healthy volunteers. Design: Prospective, randomized trial. Setting: Laboratory of the University Department of Anesthesiology. Subjects: Eight volunteers. Interventions: After a control period, dopexamine was administered using four infusion rates (0.75, 1.5, 3.0, and 6.0 mu g/kg/min). Measurements and Main Results: Blood pressure, heart rate, oxygen consumption (Vo(2)), and the plasma concentration of potassium, glucose, lactate, and norepinephrine were measured, Typical hemodynamic responses were seen. Vo(2) increased from 122 +/- 11 (SD) to 150 +/- 9 mL/min/m(2) during the highest dopexamine infusion rate. Plasma potassium concentration decreased only during the highest infusion rate, Plasma glucose concentration increased during infusion rates of 3 and 6 mu g/kg/min of dopexamine, from 90 +/- 5 to 99 +/- 5 mg/dL (5.0 +/- 0.3 to 5.5 +/- 0.3 mmol/L), and from 87 +/- 7 to 103 +/- 11 mg/dL (4.8 +/- 0.4 to 5.7 +/- 0.6 mmol/L), respectively. Lactate did not increase during dopexamine infusion. Plasma norepinephrine concentration increased during all four infusion rates. Conclusion: It was not possible to differentiate the adrenergic receptor subtype responsible for the calorigenic and metabolic effects, since the putative beta(2) adrenergic-receptor agonist, dopexamine, caused an increase in the plasma concentration of the beta(1) adrenergic-receptor agonist, norepinephrine. Since beta(2) adrenergic receptor-mediated effects such as hypokalemia were found only at infusion rates greater than or equal to 3 mu g/kg/min, the effects of dopexamine at infusion rates <3 mu g/kg/min may be mainly mediated by stimulation of dopaminergic receptors and the indirect sympathomimetic action.