Zofran Causes Prolonged QT at High Dose

Ondansetron (Zofran) Prolonged QT

On 6/29/2012, the FDA announced an a risk for prolonged QT in patients given the high dose (32mg) ondansetron injection. The Drug Safety Communication announced that the 32mg dose should be avoid and the drug’s label will be revised.  The risk appears to be dose dependent.

The most common scenario for using the higher dose is as an anti-emetic administered during chemotherapy.  The updated label will state that no single intravenous dose should exceed 16mg.

The new information on QT prolongation does not change any of the recommended oral dosing regimens for ondansetron. It also does not change the recommended lower dose intravenous dosing of ondansetron to prevent post-operative nausea and vomiting.

FDA Recommendations

The use of a single 32 mg intravenous dose of ondansetron should be avoided. New information indicates that QT prolongation occurs in a dose-dependent manner, and specifically at a single intravenous dose of 32 mg.

Patients who may be at particular risk for QT prolongation with ondansetron are those with congenital long QT syndrome, congestive heart failure, bradyarrhythmias, or patients taking concomitant medications that prolong the QT interval

Electrolyte abnormalities (e.g., hypokalemia or hypomagnesemia) should be corrected prior to the infusion of ondansetron.

The lower dose intravenous regimen of 0.15 mg/kg every 4 hours for three doses may be used in adults with chemotherapy-induced nausea and vomiting. However, no single intravenous dose of ondansetron should exceed 16 mg due to the risk of QT prolongation.

The new information does not change any of the recommended oral dosing regimens for ondansetron, including the single oral dose of 24 mg for chemotherapy induced nausea and vomiting.

– FDA Drug Safety Communication


As always, consult your medical provider and/or pharmacist before making any medication changes.  This update in no way constitutes personal medical advice.

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