The Food and Drug Administration (FDA) has issued a public safety alert regarding a potentially fatal side effect caused by a specific dose of the cancer drug, Zofran (ondanestron).
According to an update from the agency, a recently completed study submitted to the agency by British drug maker GlaxoSmithKline shows that the 32-milligram dose of Zofran, used to treat nausea suffered by cancer patients, can impact the electrical activity of the heart (QT prolongation), leading to a potentially fatal heart rhythm condition known as Torsades de Pointes.
To mitigate this risk, GlaxoSmithKline is recommending the FDA remove the 32-milligram dose recommendation from its safety label. The new labels will indicate that no single dose of the drug shall exceed 16 milligrams. Instead, Zofran should only be delivered to adults and children suffering from chemotherapy-induced nausea and vomiting. The drug is delivered intravenously or through pill form.
These dosing updates are only specific to the injected form of the drug. Regulators believe no dose higher than 16 milligrams should be given through the injection form of Zofran. This does not apply to the 24-milligram pill form of the drug.
The FDA is recommending that patients with a risk of QT prolongation should certainly avoid the highest dose of Zofran. Patients at highest risk of QT prolongation have congestive heart failure, bradyarrhythmias, or are already taking drugs that are designed to extend QT prolongation.
Patients facing the highest risk of suffering complications due to QT prolongation are those who receive a 32-milligram dose.
The agency also states that electrolyte levels should be controlled prior to delivering any Zofran medication. A person suffering from hypokalemia or hypomagnesemia may not be ready for Zofran and could face an increased risk of this life-threatening side effect.
Zofran belongs to the class of drug 5-HT3 receptor antagonists. It is most commonly prescribed to patients undergoing chemotherapy, radiation therapy, or surgery. Patients taking any of the drugs in this class do face a heightened risk of QT prolongation and other cardiac side effects. This new information helps to identify certain drugs and strengths of drugs that put patients most at risk.
The agency said it is reviewing the information it has received from GlaxoSmithKline and will make further recommendations once that is complete. The FDA, just under a year ago, said it was conducting another review of Zofran and other drugs in the 5-HT3 receptor antagonists class for a potentially increased risk of heart attack caused by them.
At that time, the FDA said it would make temporary changes to Zofran’s labeling and that GlaxoSmithKline should conduct its own review of the drug to determine the heart attack risk factors associated with it.