Acting on Peripheral Dopamine Receptors

FIGURE 35.7 Fenoldopam, which causes vasodilation, is useful in congestive heart failure. 

Dopamine stimulates dopamine, a-, and [3-adrenergic receptors. The use of dopamine in congestive heart failure is limited because it causes nausea and vomiting, becomes inactive when given orally, increases afterload (a-adrenergic receptor-mediated peripheral vasoconstriction), and enhances oxygen demand on the left ventricle. 

Dobutamine, which is available only for parenteral administration, stimulates [3,-adrenergic receptors, producing a strong inotropic effect. 

Ibopamine, which is active orally, is capable of eliciting peripheral and renal vasodilation, positive vasodilation, and a positive inotropic action. Ibopamine is converted to epinine, which is the active drug. 

Fenoldopam is an orally active DA,-receptor agonist. It is more potent than dopamine in causing renal vasodilation without having adrenergic, cholinergic, or histaminergic properties. 

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