Is it possible that there’s a link between one of the world’s most popular flu medications and unusual or erratic behavior in people who have taken it?
Odd as it seems, there have been reports that some people, in particular children in Japan, have exhibited odd behavior after taking Tamiflu, a product prescribed to treat the flu or to prevent people from catching the flu. According to these reports, FDA-approved Tamiflu may have induced delirium and other unusual behavior in some patients. While this caused some initial concern, it appears that any link between Tamiflu and unusual behavior is inconclusive.
The Japanese-Tamiflu Connection
Japan has been one of the world’s largest markets for Tamiflu since it was launched there in 2001. Some estimates suggest that nearly 70% of the people who have taken Tamiflu worldwide are in Japan. And of the 600 or so cases of unusual behavior reported among Tamiflu patients, about 75% have been from Japan.
Since 1999, Tamiflu has been taken by millions of flu-stricken adults and children without any serious side effects at all. Still, sporadic instances of erratic behavior have been reported by those taking Tamiflu. In May 2004, Japan’s Health Ministry directed that all Tamiflu sold in the country should carry a warning that using the drug could increase the risk of neurological and psychological problems.
Tamiflu Warning Labels
Both the FDA and the Swiss pharmaceutical company Roche, the maker of Tamiflu, maintained that there was no evidence linking Tamiflu to the effects observed in some patients. However, in November 2006, the FDA recommended that Tamiflu’s label be modified to include a warning that the product could cause delirium and hallucinations in some users. This action may have been prompted by an increasing number of complaints received from Tamiflu users in Japan.
In March 2007, Japan’s Health Ministry said doctors should exercise caution when prescribing Tamiflu to children between the ages of 10 and 19. Fifteen people in this age group who had taken Tamiflu were reportedly injured or killed in jumps or falls between 2004 and March 2007.
The FDA conducted a study of 596 cases, most of them in Japan, in which Tamiflu users were said to have suffered behavioral side effects. FDA authorities suggested that the Tamiflu warning label be modified, to incorporate language that is stronger and more specific.
While Tamiflu’s manufacturer expressed a willingness to change the label, it also asserted that no clear evidence has been presented to prove a connection between Tamiflu and any form of abnormal behavior. In particular, they pointed out that a severe case of the flu itself can, in some instances, trigger unusual behavior and that Tamiflu should not be blamed for that.
Inconclusive Evidence
More importantly, a Health Ministry panel in Japan studying the connection between erratic behavior and the use of Tamiflu said in an interim report released in December 2007 that no conclusive evidence has been found to link the two. In fact, one of its teams concluded after a preliminary study of 10,000 flu patients, a majority of them Tamiflu users, that the incidence of strange behavior was higher among those who did not take the drug than those who did. A second team pointed out that nearly 40% of those who had exhibited unusual behavior had not taken Tamiflu.
In Tamiflu’s corner are those who point out that no drug has ever caused a reaction that has been confined to people of a single nationality. The FDA has suggested that the high level of Tamiflu use in Japan combined with the strong awareness children there have about "brain fever" and similar ailments have accounted for a jump in the number of reported cases.
Overall, the possible connection between Tamiflu use and unusual behavior remains unproven and in fact may be non-existent. Still, patients considering taking Tamiflu as either a flu treatment or flu preventive should exercise caution and take the product only under the supervision of a licensed physician or pharmacist.
For more information about Tamiflu and the treatment and prevention of the flu, visit the online influenza knowledge base at eDrugstore.md. See the Tamiflu product information page for details regarding Tamiflu pricing and ordering.
