From the Research
Ondansetron is contraindicated in patients with congestive heart failure (CHF) because it can prolong the QT interval on the electrocardiogram, potentially leading to dangerous cardiac arrhythmias, particularly Torsades de Pointes, as supported by the most recent study in 2024 1. This risk is especially concerning in CHF patients who often have underlying cardiac electrical abnormalities, electrolyte disturbances, and may be taking other medications that also affect cardiac conduction. The QT prolongation effect of ondansetron is dose-dependent, with higher doses (particularly IV doses exceeding 16mg) carrying greater risk, as noted in a study from 2018 2. Patients with CHF frequently have reduced cardiac reserve and compromised ventricular function, making them more vulnerable to the arrhythmogenic effects of QT-prolonging medications. Additionally, many CHF patients have electrolyte abnormalities such as hypokalemia or hypomagnesemia that further increase the risk of QT prolongation and arrhythmias, as highlighted in a study from 2011 3. When antiemetic therapy is needed for patients with CHF, alternative agents such as prochlorperazine, metoclopramide, or dexamethasone should be considered, though each has its own risk profile that must be evaluated based on the individual patient's condition. A study from 2017 4 also found that ondansetron was associated with a risk of cardiac adverse events related to QT interval prolongation, which further supports the need for caution when prescribing this medication to patients with CHF. Overall, the use of ondansetron in patients with CHF should be avoided due to the potential risk of QT interval prolongation and torsades de pointes, as emphasized by the most recent evidence from 2024 1.