An updated Cochrane review, published in the British Medical Journal, challenges the historical assumption that neuraminidase inhibitors -- a class of anti-viral drugs which work by blocking the function of the viral neuraminidase protein preventing the virus from reproducing -- are effective in combating influenza.
The new analysis was possible because of the release of more complete trial data by drug manufacturers Roche and GlaxoSmithKline.
The analysis of the data indicated when used as a preventative treatment, the drug can reduce the risk of people suffering symptomatic influenza, but there was a 1 percent increase in risk of psychiatric events and an increased risk of headaches and kidney events.
However, there is no evidence it could stop people carrying the influenza virus and spreading it to others.
The review also found the anti-virals increased nausea and vomiting by 4 percent in adults and 5 percent in children. These side effects were not reported in the initial clinical trial publications.
The findings were based on the internal data of 20 Tamiflu, or oseltamivir, and 26 Relenza, or zanamivir, trials involving more than 24,000 people.
With small benefits of symptom relief, there is little to justify the global stockpiling of the drugs given the lack of reliable evidence to support the original claims of its benefits, calling into question the more than $1.3 billion spent by the United States on a strategic reserve of antivirals, the researchers said.
“We now have the most robust, comprehensive review on neuraminidase inhibitors that exists," Dr. David Tovey, editor in chief of Cochrane said in a statement. "Initially thought to reduce hospitalizations and serious complications from influenza, the review highlights that Tamiflu is not proven to do this, and it also seems to lead to harmful effects that were not fully reported in the original publications.”