Levophed (Norepinephrine) and QT Interval Prolongation
Levophed (norepinephrine) does not cause QT interval prolongation and is not listed among medications known to prolong the QT interval in any of the clinical guidelines. Unlike many other cardiovascular medications, norepinephrine is not associated with QTc prolongation risk.
Medications Known to Prolong QT Interval
According to clinical guidelines, the following medication classes are known to prolong QT interval:
- Class IA antiarrhythmics: quinidine, procainamide, disopyramide 1
- Class III antiarrhythmics: amiodarone, sotalol 1
- Fluoroquinolones: moxifloxacin, levofloxacin, ciprofloxacin 1
- Macrolides: erythromycin, clarithromycin, azithromycin 1
- Dopamine antagonists: metoclopramide, domperidone 1
- Antipsychotics: thioridazine, haloperidol, chlorpromazine 1
- Tricyclic antidepressants 1
- Antimalarials: chloroquine, hydroxychloroquine 1
- Antifungals: ketoconazole, voriconazole, itraconazole, fluconazole 1
- Methadone 1
Notably absent from these lists is norepinephrine (Levophed), which is a vasopressor commonly used in shock states.
Mechanism of Action and QT Prolongation
Most drugs that prolong the QT interval act by blocking hERG-encoded potassium channels 2. Norepinephrine works through a different mechanism:
- Norepinephrine is an alpha-1 adrenergic agonist causing vasoconstriction
- It also has beta-1 adrenergic effects increasing cardiac contractility and heart rate
- Unlike drugs that interfere with cardiac repolarization, norepinephrine does not directly affect ion channels responsible for QT interval
Clinical Implications
When treating patients requiring vasopressor support:
- Norepinephrine can be safely used in patients with baseline QT prolongation or those taking other QT-prolonging medications
- This makes it a preferred vasopressor for patients with risk factors for Torsades de Pointes
- Monitor for other potential side effects of norepinephrine including:
- Tachycardia
- Hypertension
- Tissue ischemia with extravasation
Risk Factors for QT Prolongation to Consider
While norepinephrine itself doesn't prolong QT, be aware of other risk factors that may contribute to QT prolongation:
- Female sex
- Advanced age (>65 years)
- Underlying heart disease
- Bradyarrhythmias
- Electrolyte abnormalities (particularly hypokalemia, hypomagnesemia)
- Concurrent use of QT-prolonging medications 1
- Hepatic dysfunction
Clinical Monitoring Recommendations
When managing critically ill patients on vasopressors:
- Baseline ECG is recommended before starting any medications in critically ill patients
- Regular ECG monitoring is warranted in ICU settings, especially if patients are receiving other medications that may prolong QT
- Monitor and correct electrolyte abnormalities, particularly potassium and magnesium
Conclusion
Levophed (norepinephrine) does not cause QT interval prolongation and can be safely used in patients at risk for QT prolongation. This makes it a suitable vasopressor choice for patients with baseline QT prolongation or those receiving other QT-prolonging medications.