Amrinone is best described as which pharmacologic action?

Amrinone is best described as which pharmacologic action?

• A. Is a positive inotropic drug
• B. Is antagonized by esmolol
• C. Is a vasoconstrictor
• D. Has weak antidysrhythmic properties

Answer: (A)

Amrinone works as a positive inotropic agent by inhibiting phosphodiesterase III, which raises intracellular cyclic AMP in cardiac muscle. The higher cAMP enhances calcium availability during systole, boosting contractility and stroke volume. At the same time, increased cAMP in vascular smooth muscle causes vasodilation, lowering afterload. This combination makes it an inodilator—improving cardiac output while reducing systemic vascular resistance. It isn’t a vasoconstrictor, and its action isn’t defined by antagonism with esmolol (beta-blockade may blunt effects but isn’t the primary mechanism), and it isn’t characterized as antidysrhythmic (in fact, PDE inhibitors can be proarrhythmic).

Amrinone works as a positive inotropic agent by inhibiting phosphodiesterase III, which raises intracellular cyclic AMP in cardiac muscle. The higher cAMP enhances calcium availability during systole, boosting contractility and stroke volume. At the same time, increased cAMP in vascular smooth muscle causes vasodilation, lowering afterload. This combination makes it an inodilator—improving cardiac output while reducing systemic vascular resistance. It isn’t a vasoconstrictor, and its action isn’t defined by antagonism with esmolol (beta-blockade may blunt effects but isn’t the primary mechanism), and it isn’t characterized as antidysrhythmic (in fact, PDE inhibitors can be proarrhythmic).