As expected, US health advisors have recommended that stronger warnings concerning abnormal behaviour be put on the labels on Roche and GlaxoSmithKline’s flu drugs Tamiflu and Relenza, respectively.

The US Food and Drug Administration’s Paediatric Advisory Committee has adopted suggestions by agency staffers made at the beginning of the week and says that the current prescribing information does not adequately explain the growing number reports of delirium, hallucinations and psychotic behaviour in patients who are on the drugs, most notably in Japan.

In the case of Tamiflu (oseltamivir), some committee members recommended stronger labelling to note patient deaths, while for Relenza (zanamivir), an additional warning about hallucinations and delirium has been suggested. The recommendations follow a review of around 700 cases of psychiatric adverse events for both drugs, and 25 incidences of paediatric deaths in patients taking Tamiflu reported to the FDA up until May this year. No fatalities were reported for Relenza.

Roche is not convinced that any such change is necessary and presented its own analysis at the meeting of more than 150,000 patients which showed no connection between Tamiflu and increased risk of psychiatric problems. The company said that “of all available data, based on the temporal relationship of the neuropsychiatric adverse events both to influenza and Tamiflu, it is difficult to distinguish between drug and disease”.

Roche concluded by noting that “the relative contribution of Tamiflu to the incidence or severity of the neuropsychiatric events seen in influenza patients is unknown” and that the current label “continues to be an accurate assessment of all available updated and expanded data”. Indeed, Jonathan Solsky, director of drug safety risk management at Roche, added that there is emerging data showing that abnormal behaviours may be caused by influenza alone. GSK noted that there is no evidence showing a link between Relenza and abnormal behaviours and said it does not believe a labelling update is required.

The committee agreed that no direct link with the antiviral drugs has been established, but any concerns should be made clearer to the public.