Which enzyme does milrinone inhibit to exert its therapeutic effect?

Milrinone exerts its therapeutic effect by inhibiting cyclic AMP phosphodiesterase. This enzyme plays a crucial role in the breakdown of cyclic AMP (cAMP), a secondary messenger involved in various intracellular signaling pathways. By inhibiting cyclic AMP phosphodiesterase, milrinone increases the levels of cAMP within cardiac and smooth muscle cells. Elevated cAMP levels lead to enhanced cardiac contractility (positive inotropic effect) and vasodilation, which are beneficial in the management of heart failure and other conditions where improved cardiac output is desired. This mechanism is foundational for understanding how milrinone functions in clinical settings, particularly in acute heart failure management.