U.S. Food and Drug Administration staff have recommended new warnings about psychiatric side effects seen in some patients taking Tamiflu and Relenza, according to documents released Friday.

An FDA advisory panel will review the recommendations for the anti-viral influenza drugs at a meeting next week.

In March, Japan warned against prescribing Tamiflu to patients aged 10 to 19 as more than 100 individuals, mostly young, showed signs of abnormal behaviour after taking the influenza drug.
(Associated Press)

It based its recommendations on a review of nearly 600 cases of neuropsychiatric events reported by patients on Tamiflu and 115 cases of such events by patients taking Relenza.

In the case of Tamiflu, "the number of cases continues to increase," FDA staff wrote, in one of several documents posted ahead of the meeting.

The panel meeting will be the third public meeting on the safety of Roche Holding AG's Tamiflu, originally prompted by reports two years ago of a dozen deaths of children in Japan who had been taking the drug.

Experts then found no evidence of a direct connection between the drug and the deaths, although the FDA did ultimately update Tamiflu's label to add a caution urging close monitoring of patients for abnormal behaviour such as delirium or self-injury.

In documents prepared for the meeting next week and posted on the FDA's Web site, agency staff recommended that Tamiflu's label be strengthened further to note: "In some cases, these behaviors resulted in serious injuries, including death, in adult and pediatric patients."

Consumer group Public Citizen chided the agency for failing to note the reported adverse events earlier on the label.

"What is the justification for not warning people for these adverse events that have clearly occurred?" said Dr. Sidney Wolfe, head of Public Citizen's health research arm.

"Japan has said, 'stop using the drug if these things occur.' In [the U.S.], we haven't even mentioned that deaths have occurred."

Hallucinations, delirum seen in Relenza patients

In March, Japan warned against prescribing Tamiflu to young people aged 10 to 19 as more than 100 individuals, mostly young, showed signs of abnormal behaviour after taking the drug.

Earlier this year, Japan broadened its probe of Tamiflu to look at amantadine and GlaxoSmithKline Plc's Relenza.

The FDA staff also reviewed Relenza, a drug in the same class as Tamiflu, recommending its label be changed to note "reports of hallucinations, delirium and abnormal behaviour" observed in some patients taking the drug.

The current Relenza label has no label warning related to psychiatric events.

The FDA staff said the evidence is "conflicting" as to whether the events are medication-related, a manifestation of disease or a combination of the two.

It will present the advice to the advisory panel of experts meeting on Tuesday. The agency typically takes the advice of these panels but is not bound by them.