Roche Holding AG's Tamiflu and GlaxoSmithKline Plc's Relenza, the two most common drugs used to treat and prevent flu, should carry warnings that they may cause psychiatric side effects, U.S. regulators recommended.

The report by staff members of the U.S. Food and Drug Administration was posted Friday, before a Nov. 27 advisory panel meeting scheduled to review use of the antiviral medications. Five Japanese children who took Tamiflu and became delirious died, and there were reports of abnormal behavior among some children using Relenza, mainly in Japan, the documents noted.

Regulators aren't sure if the deaths and abnormal behavior were caused by the drugs, the flu virus or a combination of both, the FDA staff members said in a Nov. 9 memo. Nor did they propose any new limits to use of the drugs.