Japan’s Ministry of Health has suggested that it is gearing up to issue another warning of behavioural side effects linked with Roche’s immensely successful flu drug Tamiflu (oseltamivir), which is being stockpiled globally in the event of a pandemic of avian flu, according to local newswires, including the Kyodo news agency.

The drugs regulator has said that it is investigating “a number” of reports of sudden death amongst children given the drug, and says it has identified 64 cases of psychological disorders linked to Tamiflu since its approval four years ago. The news follows the unveiling of data at the Japan Society of Paediatric Infectious Diseases by Rokuro Hama, head of the Japan Institute of Pharmaco-Vigilance, who said he had seen twelve deaths in children between the ages of two and 17 over the past three years that he believes can be linked to Tamiflu use.

And Chugai, which distributes Tamiflu in the country, says it has reported two deaths to the Ministry – which in turn has concluded that one death was related to the drug’s side effects. In Japan, Tamiflu is already stamped with a warning of abnormal behaviour and hallucinations, which is not on the labelling in other markets.

Meanwhile, over the weekend, the government announced that it plans to hike its own stockpiles of Tamiflu to 250 million capsules, from 150 million, The Japan Times reports.