milrinon

Milrinone is a phosphodiesterase 3 (PDE3) inhibitor used intravenously for short-term management of acute decompensated heart failure. It provides inotropic support while also causing vasodilation, helping to improve cardiac output and reduce filling pressures in hospitalized patients who have not adequately responded to other therapies.

Mechanism of action: By inhibiting PDE3, milrinone increases intracellular cyclic adenosine monophosphate (cAMP) in cardiac myocytes, which enhances calcium availability and myocardial contractility. In vascular smooth muscle, higher cAMP reduces calcium sensitivity, leading to vasodilation. The combined inotropic effect and vasodilation improve forward flow and decrease systemic and pulmonary vascular resistance.

Clinical use: Milrinone is indicated for short-term intravenous support in patients with severe or decompensated heart failure and low cardiac output, particularly in the hospital setting or around cardiac surgery. It is not intended for long-term chronic therapy, as it has not shown a survival benefit in sustained treatment and carries risks associated with inotropic/vasodilatory strategies.

Pharmacokinetics and administration: Milrinone is given by IV infusion with rapid onset of action. It has a half-life of about 2 to 3 hours and is primarily excreted unchanged by the kidneys, so dose adjustments are required in renal impairment. Patients on milrinone require continuous monitoring of blood pressure, heart rate, rhythm, and renal function, with dose modifications based on hemodynamic response and tolerance.

Adverse effects and cautions: Common adverse effects include hypotension and arrhythmias, as well as headache and nausea. Thrombocytopenia has been reported in some cases. Use with caution in patients with significant hypotension, tachyarrhythmias, or severe renal impairment, and be mindful of potential interactions with other vasodilators or inotropes.