Relenza Label Updated to Include Psychiatric Side Effect WarningsApr 2, 2008 | Parker Waichman LLP Relenza inhalation powder, a drug that lessens symptoms of flu, has had new warnings added to its label about delirium and abnormal behavior seen in patients - mostly children - treated with Relenza, GlaxoSmithKline has announced. In March, the labeling of Tamiflu, a rival flu drug made by Roche Holding AG, was also modified to include similar information.
Relenza was approved by the Food & Drug Administration (FDA) in 1999 to treat flu symptoms. Relenza is indicated for treatment of uncomplicated acute illness due to influenza A and B virus in adults and pediatric patients 7 years of age and older who have been symptomatic for no more than 2 days. Relenza is also approved to help to prevent getting influenza A and B in children and adults age 5 years and older in community and household settings
According to a letter Glaxo sent to healthcare providers dated March 11, the new warnings on neuropsychiatric events have been added to the "Warnings and Precautions" section of the Relenza inhalation powder package insert. The label now says that:
". . .there have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury in patients with influenza who were receiving neuraminidase inhibitors, including RELENZA. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made, but they appear to be uncommon based on usage data for RELENZA. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of RELENZA to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient."
In addition, the following information has been added to the Relenza Patient Information, in the, "What are important or common possible side effects of taking RELENZA?" section:
"People with influenza (the flu), particularly children and adolescents, may be at an increased risk of seizures, confusion, or abnormal behavior early in their illness. These events may occur after beginning RELENZA or may occur when flu is not treated. These events are uncommon but may result in accidental injury to the patient. Therefore, patients should be observed for signs of unusual behavior and a healthcare professional should be contacted immediately if the patient shows any signs of unusual behavior."
In November 2007, an FDA advisory panel had recommended stronger warnings about psychiatric side effects be added to the labeling of both Tamiflu and Relenza. The recommendations where based on a review of nearly 600 psychiatric adverse event reports in Tamiflu patients, and another 115 reports among people taking Relenza. Documents posted online by FDA staffers at the time said that there have been reports of 596 neuropsychiatric events, including 16 neuropsychiatric-related deaths, among children and adults taking Tamiflu. Among those reports, 75% came from Japan. In total, the FDA said, there were 25 deaths from all causes reported among Tamiflu users on a world-wide basis in patients younger than 21. Japan was also the origin of 81 of the Relenza reports, but no deaths where associated with that drug. Of the 48 million people treated with Tamiflu since its approval in 1999, the majority of users – 35 million – have been in Japan.