Japan finds Tamiflu study inconclusive, will probe more

TOKYO (Reuters) - Over half of influenza patients in Japan showing abnormal behavior had taken the drug Tamiflu, but it is not clear if there was a causal link between the drug and their actions, a government report showed on Monday.

Japan is investigating whether there is any link between Tamiflu, made by Roche Holding AG, and neuropsychiatric problems after more than 100 people, mostly young, showed erratic behavior such as jumping from buildings after taking the drug.

There have been eight cases of deaths after abnormal or possibly abnormal behavior.

Tamiflu can treat symptoms of regular seasonal influenza and is seen as one of the best defenses against a possible bird flu pandemic.

The Health Ministry report said that of 137 patients who had shown abnormal behavior, 82 had taken Tamiflu, while 52 had not.

But the report, compiled by a group of doctors and other health experts, said their figures were difficult to assess because it was not clear what percentage of all influenza patients had been prescribed Tamiflu.

The report also said that the number of patients showing abnormal behavior did not drop after the government warned in March against prescribing Tamiflu to those aged 10 to 19.

A Health Ministry official said that the study had been inconclusive but that a separate group of doctors and experts would present their own study later in the month.

"We hope to reach some kind of conclusion at that time," he said.

Roche and its Japanese partner Chugai Pharmaceutical Co Ltd have said no causal relationship has been established between Tamiflu and neuropsychiatric symptoms, and doctors say influenza itself can cause abnormal behavior.

Tamiflu, known generically as oseltamivir, is widely prescribed in Japan. Chugai estimates some 35 million people have taken the drug, accounting for around 70 percent of the world's Tamiflu consumption.

(Reporting by Chisa Fujioka; Editing by Mike Miller)