A patient with acute decompensated HFrEF who is already receiving maximally tolerated oral metoprolol requires inotropic support. Which agent is preferred precisely because its action does not depend on beta-receptor signaling?
- A Milrinone ✓
- B Dobutamine
- C Norepinephrine
- D Digoxin loading dose
Correct answer: A. Milrinone
Explanation
Milrinone inhibits phosphodiesterase type 3, increasing intracellular cAMP independently of beta-adrenergic receptors, so it retains inotropic and vasodilator activity despite full beta-blockade. Dobutamine (option B) acts through beta-1 receptors and its effect is blunted when those receptors are occupied by an antagonist. Norepinephrine raises afterload and is not chosen for low-output states here. Milrinone also lowers pulmonary vascular resistance, a useful feature in right heart failure.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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