Tamiflu, a drug used to treat the flu, has been linked to abnormal behavior and other brain side effects in more than 50 children in the United States, and tomorrow a Food & Drug Administration (FDA) advisory panel will meet to discuss what should be done about these dangerous Tamiflu side effects. Last Friday, a report prepared by FDA staffers recommended that new warnings be placed on the label of Tamiflu regarding such side effects. The FDA report also recommended new warnings for Relenza, another anti-flu drug.
Since Tamiflu was introduced in 1999, the FDA has received 55 adverse event reports involving children. Twenty-two of the Tamiflu side effects reports where considered “serious” and involved convulsions, delirium or delusions. Documents posted online last week by FDA staffers for tomorrow’s advisory panel meeting recommended new psychiatric warnings for Tamiflu and Relenza. Though Tamiflu already bears a psychiatric event warning, FDA staffers have recommended that it should be strengthened to say: “In some cases, these behaviors resulted in serious injury, including death, in adults and pediatric patients.” The recommendations also say that the Relenza label should be changed to warn of “reports of hallucinations, delirium and abnormal behavior” observed in some patients taking the drug.
The link between Tamiflu and psychiatric side effects was first reported in Japan. While none of the adverse Tamiflu events reported in the US involved fatalities, several in Japan resulted in deaths. In patients under sixteen, four adverse events involved fatal falls, and one involved a leukemia patient who developed encephalitis. Also in Japan, there where two reports of deaths in young people aged 17 to 21, one involving a “fatal accident with abnormal behavior” and another encephalitis death. In March, the Japanese Tamiflu adverse event reports prompted that country’s drug regulatory agency to restrict the use of Tamiflu. Japan also announced that it would be reviewing the safety of Relenza and another anti-flu drug, Amantadine, after those drugs were also linked to psychiatric events. Japan has been a major market for Tamiflu, and 75% of all Tamiflu prescriptions where written there.
In 2005, the FDA convened an advisory panel to discuss the problems with Tamiflu, but the panel concluded the events likely weren’t related to Tamiflu. However, the panel recommended the agency keep monitoring the drug. On November 13, 2006, the FDA alerted doctors and parents to watch for signs of bizarre behavior in children treated with Tamiflu. At that time, The FDA updated the label after receiving the 103 reports of abnormal behavior, most of which involved children in Japan.
Those reports also led the FDA to monitor Amantadine, but so far staffers are not recommending any label changes. Amantadine already has a strong warning regarding seizures and suicide attempts seen in users.