Does milrinone (a phosphodiesterase 3 inhibitor) increase or decrease blood pressure?

From the Guidelines

Milrinone typically decreases blood pressure due to its vasodilating effects, which reduce systemic vascular resistance and lower blood pressure. This inotropic medication works by inhibiting phosphodiesterase-3 (PDE3), which increases cyclic AMP levels in cardiac and vascular smooth muscle cells. While milrinone's primary effect is to increase cardiac contractility (positive inotropic effect), it simultaneously causes vasodilation in both arterial and venous vessels, leading to reduced systemic vascular resistance and decreased blood pressure, as noted in the 2022 AHA/ACC/HFSA guideline for the management of heart failure 1.

The medication's effects on blood pressure are a key consideration in its use, particularly in patients with heart failure, where maintaining adequate blood pressure is crucial for organ perfusion. According to the guideline, milrinone is administered as a continuous infusion at 0.125–0.75 mcg/kg/min, and its use requires careful monitoring of blood pressure and other hemodynamic parameters 1. The potential for hypotension is a significant concern, and patients receiving milrinone should be closely monitored for signs of excessive blood pressure reduction.

Key points to consider when using milrinone include:

• Its vasodilating effects can lead to decreased blood pressure
• It is typically administered as a continuous infusion
• Close monitoring of blood pressure and other hemodynamic parameters is necessary
• It is generally avoided in patients with severe hypotension and used cautiously in those with tenuous blood pressure, as noted in the European Heart Journal 1.

Overall, the use of milrinone requires careful consideration of its potential effects on blood pressure, as well as its benefits in improving cardiac output and reducing the workload on the heart. By understanding these effects and using the medication judiciously, clinicians can optimize its use in patients with heart failure and minimize the risk of adverse effects, as recommended in the 2022 AHA/ACC/HFSA guideline 1.

From the FDA Drug Label

During therapy with milrinone lactate, blood pressure and heart rate should be monitored and the rate of infusion slowed or stopped in patients showing excessive decreases in blood pressure

• Milrinone is a vasodilator, which means it can cause blood vessels to dilate.
• The FDA drug label states that the rate of infusion should be slowed or stopped in patients showing excessive decreases in blood pressure, implying that milrinone can cause a decrease in blood pressure.
• Therefore, milrinone decreases blood pressure 2, 2.

From the Research

Effects of Milrinone on Blood Pressure

• Milrinone is a phosphodiesterase 3 inhibitor that has been shown to have both positive inotropic and vasodilatory effects 3, 4, 5.
• Studies have demonstrated that milrinone can decrease systemic vascular resistance and mean arterial pressure in patients with congestive heart failure 3, 4, 5.
• In one study, milrinone caused a significant decrease in mean aortic pressure from 82 +/- 3 to 71 +/- 3 mmHg (P less than 0.01) 3.
• Another study found that milrinone decreased mean arterial blood pressure from 88 +/- 5 to 77 +/- 2 mmHg (p less than 0.025) 5.
• The vasodilatory effects of milrinone can lead to a decrease in blood pressure, with one study reporting a maximum decrease in diastolic blood pressure of 54.5 +/- 0.5 mmHg 6.
• However, it is worth noting that milrinone can also increase cardiac index and stroke volume, which may offset some of the decreases in blood pressure 4, 7, 5.