At which dose range does dopamine primarily cause renal vasodilation?

• A. High doses
• B. All doses equally
• C. Low doses
• D. Midrange doses

Answer: (C)

Dopamine has dose-dependent receptor effects. At low doses it preferentially activates renal dopamine D1 receptors on the renal vasculature, causing vasodilation of the afferent and efferent arterioles. This increases renal blood flow and promotes natriuresis. As the dose increases, β1 effects (increasing heart rate and contractility) become prominent, and at even higher doses α1 effects cause vasoconstriction, which can negate the renal vasodilation. Therefore, the renal vasodilatory effect occurs with the lowest dose range, roughly 0.5–3 mcg/kg/min.