Which drug is a dopamine precursor used to treat shock and to increase renal blood flow?

• A. Norepinephrine
• B. Isoproterenol
• C. Dopamine
• D. Epinephrine

Answer: (C)

Dopamine is a precursor in catecholamine synthesis to norepinephrine and epinephrine, and its clinical use in shock relies on dose-dependent receptor effects. At low doses it primarily stimulates dopamine D1 receptors in the kidneys, causing vasodilation of renal vessels and increased renal blood flow. This helps preserve kidney perfusion during shock. At intermediate doses it activates beta-1 receptors in the heart, boosting heart rate and contractility to raise cardiac output. At high doses it engages alpha-1 receptors, increasing systemic vascular resistance and blood pressure. This combination makes dopamine particularly useful in shock when maintaining renal perfusion is a goal. Other choices act mainly through different adrenergic receptors or have less renal-specific effects, so they don’t provide the same renal vasodilatory benefit seen with dopamine at its low-dose range.