From the Guidelines
For patients with prolonged QTc intervals, ondansetron (4-8 mg IV/PO every 8 hours) is the preferred anti-nausea medication due to its minimal effects on QTc prolongation when used at recommended doses. According to the study published in the Journal of the American College of Cardiology in 2017 1, ondansetron is considered a safer option compared to other anti-nausea medications that can significantly prolong the QTc interval, such as metoclopramide, domperidone, and droperidol.
When administering ondansetron to patients with prolonged QTc, it is essential to:
- Monitor the ECG before and after administration
- Maintain electrolytes (especially potassium, magnesium, and calcium) within normal ranges
- Use the lowest effective dose for the shortest duration possible The mechanism behind QTc prolongation involves blockade of hERG potassium channels in cardiac cells, which delays ventricular repolarization, as mentioned in the study 1. Patients with congenital long QT syndrome, electrolyte abnormalities, or those taking other QT-prolonging medications are at particularly high risk and require extra caution.
Key considerations for managing QTc prolongation include:
- Identifying drug-drug interactions that prolong the QTc interval
- Correcting electrolyte abnormalities prior to starting treatment
- Repeating ECG monitoring at 7 days after initiation of therapy and following any dosing changes, as recommended by the 2016 Canadian Cardiovascular Society guideline 1
- Discontinuing QT-prolonging medications and correcting electrolyte abnormalities if Torsades de Pointes (TdP) occurs, and managing TdP with 2g of IV magnesium as the initial drug of choice, regardless of serum magnesium level 1.
From the FDA Drug Label
5.2 QT Prolongation Electrocardiogram (ECG) changes including QT interval prolongation have been seen in patients receiving ondansetron.
PRECAUTIONS General Dolasetron should be administered with caution in patients who have or may develop prolongation of cardiac conduction intervals, particularly QTc
Anti-nausea medications to avoid with prolonged QT intervals:
- Ondansetron: due to the risk of QT interval prolongation and Torsade de Pointes, especially in patients with congenital long QT syndrome or those taking other medications that lead to QT prolongation 2.
- Dolasetron: should be administered with caution in patients with prolonged QT intervals, particularly QTc, due to the potential risk of QT prolongation 3.
No conclusion can be drawn on which anti-nausea medication is safe to give to patients with prolonged QT intervals.
From the Research
Anti-Nausea Medications and QTc Intervals
- Patients with prolonged QTc intervals require careful consideration when administering anti-nausea medications, as some medications can further prolong the QTc interval and increase the risk of ventricular dysrhythmias 4, 5, 6, 7, 8.
Medications to Avoid or Use with Caution
- Ondansetron has been shown to prolong the QTc interval and increase the risk of ventricular dysrhythmias, particularly at higher doses (8 mg) 4, 8.
- Dolasetron has a precaution in its FDA labeling concerning QTc prolongation and has been associated with a higher risk of ventricular arrhythmias and cardiac arrest compared to other 5-HT3 receptor antagonists 6.
Alternative Medications
- Granisetron has not been associated with a significant risk of QTc prolongation and may be a safer alternative for patients with prolonged QTc intervals 6.
- Palonosetron has a precaution in its FDA labeling concerning QTc prolongation, but has been shown to have a lower risk of QTc prolongation compared to dolasetron 6.
Clinical Considerations
- Patients with prolonged QTc intervals should be closely monitored for signs of ventricular dysrhythmias and cardiac arrest when receiving anti-nausea medications 4, 5, 7.
- The risk of QTc prolongation should be carefully weighed against the benefits of anti-nausea medication, and alternative medications or doses should be considered when possible 4, 5, 6, 7, 8.