Milrinone is a selective inhibitor of peak cAMP phosphodiesterase III isozyme in cardiac and vascular smooth muscle. Its inhibitory action on phosphodiesterase results in increased cAMP levels, which in turn increases contractility in cardiac muscle and stimulates vasodilation in blood vessels. This causes an increase in cardiac output and a decrease in pulmonary wedge pressure. These hemodynamic changes are obtained without excessive changes in heart rate or increase in myocardial oxygen consumption.

Milrinone’s use has been best studied in patients with congestive heart failure. It appears to be very efficacious in nonhypotensive patients with acute nonischemic cardiomyopathy despite treatment with diuretics. These patients benefit from an enhancement in contractility and afterload reduction. Additionally, milrinone is known to provide enhanced diastolic function. Duration of therapy should last for 48 to 72 hours. There are no studies to date that support its use for a longer period. Long-term oral therapy with milrinone has been associated with increased mortality.

The recommended dose in patients with normal renal function is a 50-mcg/kg bolus followed by a continuous infusion at 0.375 to 0.75 mcg/kg/min. Because milrinone is excreted mainly through the kidneys, its dose in patients with renal impairment should be adjusted accordingly (by surface area) (CrCl denotes creatinine clearance):