Can Levophed (norepinephrine) increase heart rate, specifically causing tachycardia?

Can Levophed Increase Heart Rate?

Yes, Levophed (norepinephrine) can increase heart rate, though it typically causes less tachycardia than other vasopressors like epinephrine due to its predominant alpha-adrenergic effects.

Pharmacological Mechanism

Norepinephrine (Levophed) has the following receptor activity:

• Primarily alpha-1 adrenergic effects: Causes vasoconstriction
• Modest beta-1 adrenergic effects: Can increase heart rate and cardiac contractility
• Minimal beta-2 adrenergic effects: Limited vasodilation

Heart Rate Effects of Norepinephrine

Norepinephrine's effect on heart rate is complex:

1. Direct chronotropic effect: Through beta-1 receptor stimulation, norepinephrine can directly increase heart rate 1

2. Reflex bradycardia: The increase in blood pressure from alpha-1-mediated vasoconstriction often triggers a compensatory reflex decrease in heart rate 1

3. Net effect: In most patients, norepinephrine causes "less increase in heart rate" compared to epinephrine, but can still cause tachycardia in some patients 1, 2

Clinical Evidence of Tachycardia with Norepinephrine

Several studies and guidelines document norepinephrine's potential to increase heart rate:

• The European Society of Cardiology guidelines state: "Norepinephrine-induced increases in heart rate are less than with epinephrine" - indicating that some heart rate increase does occur 1

• Case reports have documented tachyarrhythmias with even low-dose norepinephrine administration 2

• In patients with atrial fibrillation and sepsis, norepinephrine was associated with higher heart rates compared to phenylephrine (a pure alpha-agonist) 3

Comparison with Other Vasopressors

When considering heart rate effects:

1. Epinephrine causes significantly more tachycardia than norepinephrine due to stronger beta-adrenergic effects 4

2. Phenylephrine (pure alpha-agonist) typically causes reflex bradycardia rather than tachycardia 3, 5

3. Norepinephrine falls between these two, with modest potential to increase heart rate 1

Clinical Considerations and Monitoring

When using Levophed:

• Monitor heart rate: The FDA label for Levophed recommends frequent monitoring of vital signs, including heart rate 6

• Risk factors for tachycardia: Patients with pre-existing arrhythmias, hypoxia, or hypercarbia may be more susceptible to norepinephrine-induced tachycardia 6

• Drug interactions: Monoamine oxidase inhibitors (MAOIs) and certain anesthetics can potentiate the cardiovascular effects of norepinephrine, including tachycardia 6

Summary

While norepinephrine primarily increases blood pressure through vasoconstriction with less effect on heart rate than epinephrine, it still has beta-1 adrenergic activity that can increase heart rate in some patients. The net effect on heart rate depends on the balance between direct chronotropic effects and reflex responses to increased blood pressure.