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Tamiflu and Relenza Need Stronger Warnings, FDA Panel Says

Nov 28, 2007 | Parker Waichman Alonso LLP

Tamiflu and Relenza, drugs used to treat the flu, should bear warnings about possible psychiatric side effects, a Food & Drug Association (FDA) panel said yesterday.  The recommendation came in the wake of a number of reports that both Tamiflu and Relenza had been linked to episodes of abnormal behavior that included delirium and hallucinations.  Many of the reports involved children treated with Tamiflu or Relenza, and some where fatal.

The FDA advisory panel 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 last week 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.

Although no direct link with the antiviral drugs has been established, the advisory panel recommended adding the new case reports to the Relenza and Tamiflu labels. It was noted that some of the abnormal behavior was seen in flu patients who did not take the drugs, suggesting a possible link to the disease itself.  While some panel members did favor mentioning the fatalities associated with Tamiflu on a new label, a formal vote on that issue was not taken. The panel voted to generally note the newly reported cases of neuropsychiatric behavior seen with Relenza.

Officials from GlaxoSmithKline, the maker of Relenza, and Tamiflu manufacturer Roche AG said they opposed label changes and cited data showing no causal link between the drugs and adverse events. It is "very difficult to differentiate drug from disease," Dr. Jonathan Solsky of Roche told the panel.

One panel member who favored stronger warnings on Tamiflu and Relenza said that the benefits of the drugs where not enough to warrant the psychiatric risks associated, even though they are rare events.  In most cases, Tamiflu or Relenza will only shorten the duration of the flu by about one day.

The flu virus is a major cause of death and illness in the United States. Complications from the illness kill about 36,000 Americans a year, a government expert told the panel. Children and the elderly are especially at risk.

The FDA is under no obligation to follow the recommendations of the advisory panel, although in most cases is does so.