Japanese study finds no behavioral effects from Tamiflu

Jul 11, 2008 (CIDRAP News) – A Japanese health ministry official said today that a government-supported study has found no evidence that the antiviral drug oseltamivir (Tamiflu) causes abnormal behavior in young people, according to a Reuters report.

The unnamed ministry official said the findings would be presented to the government's drug safety panel, which might withdraw a warning it issued in March 2007 against prescribing the drug for people between ages 10 and 19, Reuters reported today.

"The timing of the presentation is not decided, but we want to do it as soon as possible," the official told Reuters. Nikkei News, a Japanese financial newspaper, reported that the study included 10,000 people younger than 18 who were diagnosed with seasonal influenza in 2006 and 2007, according to Reuters.

Oseltamivir, a neuraminidase inhibitor, is used to prevent and treat seasonal influenza. Because it is considered the most promising drug to date for use during an influenza pandemic, the United States and many other countries are stockpiling it.

However, reports of self-injury and delirium in some Japanese children and adolescents who took the drug have raised concerns among regulators in other countries, including the United States. Some of the reported adverse events included the deaths of adolescent patients who fell from windows or balconies or ran into traffic.

Japan has also reported abnormal behaviors in young people who took zanamivir (Relenza), an inhaled neuraminidase inhibitor.

However, three rounds of review by the US Food and Drug Administration (FDA) have found no evidence that oseltamivir contributed to neuropsychiataric events. Despite the findings, the FDA this spring advised Roche, the maker of Tamiflu, and GlaxoSmithKline, the maker of Relenza, to add warnings about the reported neuropsychiatric effects to the drug labels.

In February, the FDA and Roche sent a letter to US healthcare professionals about the labeling change. The letter acknowledged the reports, noted that the role of Tamiflu in the events had not been established, and advised that flu patients should be monitored for signs of abnormal behavior. In March, Glaxo sent a similar letter to doctors regarding labeling changes for Relenza.

See also:

Feb 2008 Roche and FDA letter to health professionals

Mar 2008 Glaxo and FDA letter to health professionals

Nov 27, 2007, CIDRAP News story "FDA panel seeks stronger label warnings for 2 flu drugs"

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