Effects of Dopamine in Man

Dopamine, the biochemical precursor of norepinephrine, was infused intravenously into 11 normal subjects and 2 patients. Results of hemodynamic studies in 6 normal subjects indicated that dopamine increased cardiac output and stroke volume in all subjects. Arterial pressure also increased in all subjects with a predominant systolic pressure increment. Calculated vascular resistance decreased in 5 subjects and did not change in the other subject. Changes in heart rate were of small magnitude and were inconstant in direction. Left atrial pressure did not change in 2 patients at a time when substantial increments in cardiac output were produced by dopamine. Comparison of the doses of dopamine and norepinephrine calculated to produce equivalent increments in systolic pressure indicated that dopamine was 1/25 to 1/56 as potent as norepinephrine in this respect. Infusions of dopamine produced relatively small but consistent increments in blood glucose levels. It is concluded that the pharmacological actions of dopamine in man are different from those of epinephrine and norepinephrine. Because of its distinctive properties, dopamine may be useful in the treatment of patients with inadequate cardiac output.