Zofran (ondansetron) causes dose-dependent QT prolongation

GlaxoSmithKline would like to inform healthcare professionals of the safety concern of dose-dependent QT prolongation associated with the use of intravenous (IV) Zofran and the new dose restrictions for this product. A recent study has demonstrated that the highest test dose of 32 mg IV Zofran infused over 15 minutes caused a maximum mean QTc interval prolongation of approximately 20 milliseconds, suggesting a potential for increased risk of cardiac arrhythmia. The 32 mg IV dose is no longer recommended and should not be used. For the prevention of chemotherapy induced nausea and vomiting from moderate and highly emetogenic chemotherapy in adults, IV Zofran may still be used as described in the local prescribing information except that no dose greater than 16 mg IV (infused over at least 15 minutes) should be used. Post-marketing cases of Torsade de Pointes have been reported in patients using ondansetron. Ondansetron should be avoided in patients with congenital long QT syndrome and administered with caution to patients who have or may develop prolongation of QTc. Please refer to the letter for more details.