Warnings are being issued concerning the drug Tamiflu by both the drug company Roche and the Food and Drug Administration (FDA) in the U.S.
Tamiflu (Oseltamivir) is an antiviral drug that is used in the treatment and prevention of both Influenza virus A and Influenza virus B.
The drug is approved for the treatment of patients with flu and now both the FDA and drug maker Roche are warning of possible psychiatric side effects.
According to the FDA the label of the drug is being updated to include the potential for psychiatric side effects associated with the drug which include delirium and other abnormal behaviour, including death in some cases.
The Tamiflu label will in future warn that "patients with influenza should be closely monitored for signs of abnormal behaviour."
The majority of abnormal reactions to Tamiflu have been reported in Japan where an estimated 35 million people have been treated with oseltamivir; in total an estimated 50 million have been treated.
Since its approval for the treatment and prevention of influenza in patients over one year of age in 1999, Tamiflu has been given to over 20 million children.
Continuing worries over the likelihood of a bird flu pandemic have meant governments, corporations, and even some private individuals have stockpiled the drug as a safeguard.