Tamiflu and Relenza, antiviral drugs stockpiled by governments to tame influenza outbreaks, haven't been proven to prevent pandemics and may cause more harm in some patients than good, researchers said after reviewing 170,000 pages of trial data.

The findings, in the journal BMJ, came from the Cochrane Collaboration, a nonprofit British research group using information from Roche Holding AG, maker of Tamiflu, and GlaxoSmithKline P.L.C., which sells Relenza.

The United States has spent $1.3 billion stockpiling the drugs after a 2009 outbreak of the H1N1 swine flu. The Cochrane researchers, who examined the reports of 20 Tamiflu trials and 26 Relenza studies, found that Tamiflu cut flu symptoms for adults by 17 hours without curbing hospitalizations. Tamiflu also caused vomiting, delirium, and loss of kidney function in some patients. There was no evidence that using the treatments could stop a massive outbreak, the researchers said.

"There's no credible way these drugs could prevent a pandemic," said study author Carl Heneghan, a professor of evidence-based medicine at the University of Oxford. Money spent on stockpiling "has been thrown down the drain."

Policy-makers can't rely on drugmakers for unbiased data, said Fiona Godlee, editor-in-chief of the BMJ. -Bloomberg News