3,4-dihydroxyphenylethylamine; an intermediate in tyrosine metabolism and precursor of norepinephrine and epinephrine; iaccounts for 90% of the catecholamines; its presence in the central nervous system and localization in the basal ganglia(caudate and lentiform nuclei) suggest that dopamine may have other functions.

Syn: 3-hydroxytyramine, decarboxylateddopa.EffectsDopamine has a variety of pharmacologic characteristics that make it useful in critically ill patients. In low doses , dopamine affects primarily the dopaminergic receptors. Activation of these receptors causes vasodilation ofthe renal and mesenteric vasculature and mild vasoconstriction of the peripheral bed, which thereby redirects blood flow tokidneys and bowel.

At these low doses, the net effect on the overall vascular resistance may be slight. As the dose rises, betal-receptor activity predominates and the inotropic effect on the myocardium leads to increasedcardiac output and blood pressure. Above 10 mg/(kg-min), alpha-receptor stimulation causes peripheral vasoconstriction,shifting of blood from extremities to organs, decreased kidney function, and hypertension.

At all doses, the diastolic bloodpressure can be expected to rise; since coronary perfusion is largely a result of the head of pressure at the coronary ostiacoronary blood flow should be increased..

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