FACTBOX-What's behind warning on bird flu drug Tamiflu?

(Reuters) - The Japanese government has ordered the importer of the bird flu drug Tamiflu to warn doctors against giving it to teenagers, the Health Ministry said on Wednesday.

Here are some key facts on Tamiflu and why warnings about its use have been called for:

SIDE EFFECTS?:

- According to Japan's Health Ministry, 54 people have died after taking Swiss drugmaker Roche's antiviral flu drug Tamiflu. Two young people who took it fell to their deaths in February 2007 in suspected suicides and two others were injured in similar incidents.

- The drug's possible side effects first came to light in Japan in 2005, after 12 children died and 32 experienced abnormal behavior after taking it.

- Japan's warning will recommend the drug is not prescribed to minors over the age of 10, unless a case is judged high risk.

U.S, CANADA, AND JAPAN ASK FOR WARNINGS:

- In early November 2006 U.S. regulators announced Tamiflu would come with a new caution urging close monitoring of patients for abnormal behavior, based on more than 100 international reports of side-effects such as hallucinations, panic attacks, convulsions and self-harm.

- Later the same month Health Canada also asked Roche to include a warning on Tamiflu's possible health risks.

WHAT'S SPECIAL ABOUT TAMIFLU USE IN JAPAN?:

- Most reported cases of potentially Tamiflu-related psychiatric problems -- 95 of the 103 cases the U.S. Food and Drug Administration (FDA) cited last year -- were recorded in Japan. They included suicides and involved children.

- Japan is the world's heaviest user of Tamiflu, according to Roche. During the 2004/2005 influenza season Roche estimates around six million of the 16 million people infected with flu took the drug.

ROCHE DENIES THE DRUG CAUSES PSYCHIATRIC SYMPTOMS:

- Roche said on March 20, 2007, that new data showed there is no established causal link between neuropsychiatric symptoms and Tamiflu, which it estimates has been used by more than 42 million people since 1999.

HISTORY OF ITS DEVELOPMENT:

- Roche Holding AG acquired worldwide rights to develop and market the antiviral medicine in 1996; and holds the patent for Tamiflu until 2016.

- Tamiflu was launched in the U.S., Canada and Switzerland in 1999/2000, in Japan in 2001, and in all key European markets by 2002/2003.

GLOBAL STOCKPILES:

- Stockpiled in 75 countries on the World Health Organization (WHO)'s recommendation, it is seen as the key treatment against a possible pandemic triggered by bird flu.

- Current supplies of Tamiflu and flu vaccine production capacity would, however, be inadequate to meet world demand in a pandemic; and doses are mainly based in rich countries.

PROJECTED 2007 SALES:

- Worldwide, Roche expects that sales of Tamiflu to governments building stockpiles in case of a pandemic will be lower this year than last; at between 0.8 billion Swiss francs and 1.2 billion francs