Which statement is NOT an effect of milrinone?

Which statement is NOT an effect of milrinone?

• A. Decreases Na+ current in cardiomyocytes
• B. It increases intracellular cAMP
• C. It causes systemic vasodilation
• D. It increases calcium influx in cardiac myocytes

Answer: (A)

Milrinone works by inhibiting phosphodiesterase-3, which prevents breakdown of cAMP. With higher cAMP inside cardiac and vascular cells, you get increased signaling that boosts heart muscle performance and relaxes vessels. In the heart, cAMP activates protein kinase A, which increases calcium entry through L-type calcium channels and enhances calcium release from stores, raising contractility. At the same time, phosphorylation events improve calcium reuptake during relaxation, aiding lusitropy. In vascular smooth muscle, elevated cAMP promotes relaxation, leading to systemic vasodilation. So increasing intracellular cAMP, and the resulting higher calcium influx in cardiac myocytes along with vasodilation, are expected effects. The statement about decreasing Na+ current in cardiomyocytes does not fit milrinone’s mechanism, as milrinone’s actions are not centered on altering sodium channels.

Milrinone works by inhibiting phosphodiesterase-3, which prevents breakdown of cAMP. With higher cAMP inside cardiac and vascular cells, you get increased signaling that boosts heart muscle performance and relaxes vessels. In the heart, cAMP activates protein kinase A, which increases calcium entry through L-type calcium channels and enhances calcium release from stores, raising contractility. At the same time, phosphorylation events improve calcium reuptake during relaxation, aiding lusitropy. In vascular smooth muscle, elevated cAMP promotes relaxation, leading to systemic vasodilation.

So increasing intracellular cAMP, and the resulting higher calcium influx in cardiac myocytes along with vasodilation, are expected effects. The statement about decreasing Na+ current in cardiomyocytes does not fit milrinone’s mechanism, as milrinone’s actions are not centered on altering sodium channels.