A patient admitted with acute decompensated heart failure is on chronic carvedilol therapy and has low-output features despite adequate filling pressures. An inotrope that retains effectiveness because it acts distal to the blocked beta-receptor is:
- A Dobutamine
- B Milrinone ✓
- C Norepinephrine
- D Isoproterenol
Correct answer: B. Milrinone
Explanation
Milrinone inhibits phosphodiesterase-3, slowing cAMP degradation inside cardiac myocytes and vascular smooth muscle. It therefore raises intracellular cAMP independent of beta-receptors, producing inotropy plus vasodilation even in patients fully beta-blocked, a common clinical scenario. Dobutamine and isoproterenol require intact beta-receptors and lose potency under chronic beta-blockade, while norepinephrine raises afterload and is inappropriate for low-output heart failure.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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