What cardiac risk is associated with Zofran (ondansetron)?

What cardiac risk is associated with Zofran (ondansetron)?

• A. Hypotension
• B. Renal failure
• C. Increased QT interval and torsades de pointes
• D. Tachycardia

Answer: (C)

Ondansetron can prolong the QT interval by blocking cardiac IKr potassium channels, which delays ventricular repolarization and can lead to torsades de pointes, a dangerous form of polymorphic ventricular tachycardia. This risk is higher with higher IV doses, in people with preexisting QT prolongation, electrolyte disturbances (low potassium or magnesium), congenital long QT syndrome, bradycardia, or when given with other QT-prolonging drugs. In most patients without these risk factors the risk is low, but in at‑risk individuals it’s important to monitor the ECG or consider alternatives and correct electrolytes if needed. While hypotension or tachycardia can occur, they are not the hallmark cardiac risk associated with ondansetron; the main concern is QT prolongation and torsades de pointes.

Ondansetron can prolong the QT interval by blocking cardiac IKr potassium channels, which delays ventricular repolarization and can lead to torsades de pointes, a dangerous form of polymorphic ventricular tachycardia. This risk is higher with higher IV doses, in people with preexisting QT prolongation, electrolyte disturbances (low potassium or magnesium), congenital long QT syndrome, bradycardia, or when given with other QT-prolonging drugs. In most patients without these risk factors the risk is low, but in at‑risk individuals it’s important to monitor the ECG or consider alternatives and correct electrolytes if needed. While hypotension or tachycardia can occur, they are not the hallmark cardiac risk associated with ondansetron; the main concern is QT prolongation and torsades de pointes.