Which statement describes a disadvantage of dopamine therapy?

Which statement describes a disadvantage of dopamine therapy?

• A. Increases renal perfusion reliably improves kidney function
• B. Indirect acting component may become less effective if norepinephrine stores are depleted
• C. High doses cause improved renal function due to vasodilation
• D. Dopamine has no effect on myocardial oxygen consumption

Answer: (B)

Dopamine works through a mix of receptor effects and an indirect action that relies on the body's own norepinephrine stores. At low doses it dilates renal vessels, at moderate doses it boosts heart rate and contractility, and at high doses it can constrict vessels. An important part of its effect comes from causing the release of norepinephrine from nerve endings, which adds to its pressor and inotropic effects. If norepinephrine stores are depleted, that indirect component weakens or disappears, so dopamine’s overall effect becomes less predictable and less powerful. In other words, its ability to raise blood pressure or cardiac output can be blunted in states where the body's own catecholamines are depleted, making this a notable disadvantage of dopamine therapy. Context on the other options: relying on renal perfusion to reliably improve kidney function is not supported in practice, so that idea isn’t accurate. High doses don’t improve renal function through vasodilation; they often cause vasoconstriction via alpha effects. And dopamine does affect myocardial oxygen consumption by increasing heart rate and contractility, which increases oxygen demand.

Dopamine works through a mix of receptor effects and an indirect action that relies on the body's own norepinephrine stores. At low doses it dilates renal vessels, at moderate doses it boosts heart rate and contractility, and at high doses it can constrict vessels. An important part of its effect comes from causing the release of norepinephrine from nerve endings, which adds to its pressor and inotropic effects.

If norepinephrine stores are depleted, that indirect component weakens or disappears, so dopamine’s overall effect becomes less predictable and less powerful. In other words, its ability to raise blood pressure or cardiac output can be blunted in states where the body's own catecholamines are depleted, making this a notable disadvantage of dopamine therapy.

Context on the other options: relying on renal perfusion to reliably improve kidney function is not supported in practice, so that idea isn’t accurate. High doses don’t improve renal function through vasodilation; they often cause vasoconstriction via alpha effects. And dopamine does affect myocardial oxygen consumption by increasing heart rate and contractility, which increases oxygen demand.