The US Food and Drug Administration has launched an investigation into 12 deaths among children in Japan who were taking Roche’s influenza treatment Tamiflu (oseltamivir).

Four of the 12 cases involved sudden death, which is very rare in children with flu, according to the agency. The review will look into these as well as cases of severe skin and hypersensitivity reactions with the drug.

The US probe follows a similar investigation by the Japanese regulatory authorities over the safety of Tamiflu, launched earlier this week. In a statement, the agency noted that it the clustering of adverse events report from one country was unusual enough to prompt its investigation.

It may suggest that there are genetic causes underlying the phenomenon, although usage of the drug in Japan is also higher. IMS Health data suggests that around 24.4 million prescriptions for oseltamivir were dispensed in Japan between 2001 and 2005, compared to approximately 5.5 million prescriptions in the USA, according to a report on

Roche’s drug will be one of eight under review by an FDA panel of experts later today. The Pediatric Advisory Committee has decided to conduct an in-depth review of Tamiflu in light of the Japanese deaths, as well as data suggesting that the drug can cause ‘unusual neurologic or psychiatric events such as delirium, hallucinations, confusion, abnormal behavior, convulsions, and encephalitis’.

Roche maintained earlier this week that it was aware of no behavioural disturbances linked to Tamiflu, after its Japanese unit Chugai reported two cases of suicide in teenage boys taking the drug.

Meanwhile, the European Medicines Agency has also asked for additional data from Roche on the drug, although it stressed that no causal relationship has been seen between the drug and the behavioural symptoms.

Tamiflu is being stockpiled by governments around the world in case of a human pandemic of avian bird flu. Sales of the drug doubled in the third quarter to about $211 million.