As a result, the FDA will examine these reports as part of is annual safety review that will now cover Tamiflu and seven other drugs.
As we reported on Tuesday, Japan’s Health Ministry had reported that two teenage boys died shortly after they took Tamiflu. It then issued a warning saying that Tamiflu may induce “strange behavior.”
So far, Tamiflu has not been associated with any deaths in the United States or Europe. Experts say that the current information regarding the 12 deaths in Japan is still not definitive enough to establish a causal relationship between the drug and an increased risk of mortality.
The FDA also has information regarding 32 “neuropsychiatric events” associated with Tamiflu. All but one of these events, which included delirium, hallucinations, convulsions and encephalitis, were reported by Japanese patients.
Roche Holding AG, manufacturers of Tamiflu, and Japanese health authorities have not issued warnings or initiated any other actions for the time being.
Dr. Murray Lumpkin, the deputy commissioner of the FDA, said that “millions and millions” of patients have used the drug to treat flu without experiencing adverse health risks or an increased risk of death. He also cautioned, however, that any report of a death or other serious adverse event associated with a drug should be investigated.
A complicating factor in the current Tamiflu situation is that the reports involving the adverse reactions and the 12 Japanese deaths, list symptoms already commonly associated with the flu. Therefore it becomes difficult to determine whether the flu is causing the negative effects or if the drug is responsible for increasing these health risks.
In response to the 12 Japanese deaths, Roche reported that several studies conducted in the United States and Canada have yielded results which indicate that death incidence rate of influenza patients who were treated with Tamiflu was far lower than individuals who did not.
The drug manufacturer has also provided the FDA with two other studies regarding the safety of Tamiflu in pediatric patients. In a prepared statement, the company claimed: "Roche has carefully reviewed these events and has concluded that a causal link cannot be established."
The Japanese distributor of Tamiflu has told health officials, however, that a link between Tamiflu and increased risk of death should not be ruled out until further studies are conducted.
Currently, nausea and vomiting are the most serious side effects listed on US labels but labels in Japan include all reported adverse events such as impaired consciousness, abnormal behavior and hallucinations. These adverse events are listed even if they cannot be directly attributed to the drug.
Tamiflu is one of only two anti-viral drugs believed to be effective in treating avian flu. The other is Relenza.