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Dear Healthcare Professional Letter on the new information on dosing of ondansetron (Zofran) for intravenous use due to the association with QT prolongation


GlaxoSmithKline d.o.o., in consultation with the Agency for Medicinal Products and Medical Devices (HALMED), has sent a letter to healthcare professionals on the new information related to dosing of intravenous ondansetron used to prevent chemotherapy-induced nausea and vomiting (CINV). This includes new recommendations for repeated dosing and application in elderly patients.

This is a new, additional information to the previous recommendation to healthcare professionals that HALMED made publicly available on the 13 August 2012 (in Croatian) on its webpages.


  • Patients in the age of 75 and above: single dose of intravenous ondansetron for prevention of chemotherapy-induced nausea and vomiting, must not exceed 8 mg (infused over at least 15 minutes)
  • Adult patients under 75: single dose of intravenous ondansetron for prevention of chemotherapy-induced nausea and vomiting in adult patients (under 75 years), must not exceed 16 mg (infused over at least 15 minutes)
  • Repeated dosing in all adult patients (including older patients): repeated intravenous dosing of ondansetron must be in intervals of at least 4 hours
  • Dilution and application in elderly patients in the age of 65 and above: every doses of the intravenous medicinal product must be diluted with 50-100 ml of physiological or any other compatible solution and infused over at least 15 minutes.

The letter does not represent the entire ondansetron risk profile and healthcare professionals are advised to see the Summary of Product Characteristics.

Additional information on the safe use of ondansetron

The prolongation of the corrected QT interval (QTc) is a change in electrocardiogram indicating a risk of "Torsade de Pointes” - abnormal and potentially fatal heart rhythm. This risk has been known before and listed in the Summary of Product Characteristics.

In 2012 results of a clinical study became available demonstrating that the ratio of ondansetron and corrected QT interval prolongation is dose dependent. Based on the analysis of those results, recommendations for dosing have been changed, about which a dear Healthcare Professional Letter was sent in 2012.

New, additionally modified recommendations for dosing included in this letter, resulted from additional analysis from the above clinical study. The summary of Product Characteristics for Zofran has been changed to include these recommendations.

Here you may view the Dear Healthcare Professional Letter (in Croatian).

HALMED has not received any adverse reaction report to ondansetron that may be associated with prolongation of corrected QT interval. HALMED will continue to closely monitor the safe use of ondansetron and inform the public promptly bout any new finding.

We remind healthcare professionals that they should report any adverse reaction to HALMED, as well as quality defect. Patients who have developed any adverse reaction to medicinal product may report it directly to HALMED via form or on-line application, with recommendation regarding any adverse reaction they discover to consult with their doctor or pharmacist about the continuation of their therapy.