Oseltamivir phosphate—Lifting the restriction on its use to treat teenagers with influenza in Japan

PURPOSE: In 2007, Ministry of Health, Labour and Welfare (MHLW) warned to refrain from prescribing oseltamivir for teenagers when two Japanese teenagers with influenza fell from a high-rise building after taking oseltamivir. Revisions of the warning texts of anti-influenza drugs were discussed by the Subcommittee of Pharmaceutical Affairs and Food Sanitation Council, MHLW, based on the studies and trends of anti-influenza medication over the last 10 years. METHOD: The research group led by Dr Nobuhiko Okabe conducted nationwide survey since the 2007/2008 influenza season. The results of Japanese and foreign epidemiological and non-clinical studies of abnormal behaviors in influenza patients since 2009 were reviewed. RESULT: Severe abnormal behaviors have been reported in influenza patients taking all types of anti-influenza drugs, as well as in untreated patients. There are some risks to patients whether treated with any anti-influenza drug, or non-treated though it is still not possible to rule out a potential causal relationship between abnormal behaviors and anti-influenza drugs. 70% of abnormal behaviors occurred within two days after the onset of fever. No difference was found between anti-influenza drugs treated and non-treated patients. In patients receiving oseltamivir and other anti-influenza drugs, the frequency of abnormal behaviors is not clearly different between teenagers and patients under 10 years old. CONCLUSION: The specific "boxed warning" and the restriction only for oseltamivir that should not be used for teenagers was lifted. Therefore, the labeling of all anti-influenza drugs carry a consistent warning about the potential for abnormal behaviors in Japan.