A 62-year-old man with acute decompensated heart failure is started on dobutamine infusion for its inotropic effect. Dobutamine produces its cardiac effects primarily through which receptor profile?

• A Pure beta-1 agonism only
• B Dopaminergic D1 agonism with beta-1 effects
• C Predominant alpha-1 agonism with mild beta effects
• D Predominant beta-1 agonism with mild beta-2 and alpha-1 effects ✓

Explanation

Dobutamine is a racemic mixture: the (+) isomer is a beta-1 and beta-2 agonist and alpha-1 antagonist, while the (-) isomer is an alpha-1 agonist. The net clinical effect is predominant beta-1 mediated inotropy with some vasodilation from beta-2 activation. It is not a pure beta-1 agonist like dobutamine is sometimes mischaracterized, but rather has mixed receptor activity. Dopamine, not dobutamine, acts on B1 receptors at low doses.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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