A new study questions the effectiveness of Tamiflu (oseltamivir) and Relenza (zanamivir) in preventing or reducing flu symptoms.
Health agency recommendations for the use of antivirals were based in part on findings from trials by drug manufacturers, including GlaxoSmithKline (GSK), Medical News Today (MNT) reports. Cochrane Review researchers hoped to verify the safety and effectiveness of neuraminidase inhibitors, but manufacturers refused to provide full access to clinical trial data, leading the researchers to question whether the risks and benefits of the antivirals have been accurately reported, and whether the drugs should be stockpiled for the treatment of seasonal and pandemic flu. The U.S. has spent over $1.3 billion on reserves of influenza antivirals.
Tamiflu is used in patients two weeks of age and older whose symptoms have not lasted longer than two days, and it can be used to prevent flu in patients age one and older. Relenza is used in patients 7 and older and for flu prevention in those 5 and older, according to Medical News Today.
The British Medical Journal (BMJ) put pressure on Roche – the manufacturer of Tamiflu – to release trial data for the drug. When the Cochrane researchers gained access to original clinical trial data, they analyzed 20 full internal reports on the effects of Tamiflu and 26 reports on the effects of Relenza. The reports included more than 24,000 people, according to MNT. Among the findings: Tamiflu led to faster relief of flu symptoms by only half a day (from 7 days to 6.3 days), compared with a placebo. It did not reduce hospitalizations or complications such as pneumonia, bronchitis, sinusitis or ear infections in either adults or children. Tamiflu increased nausea and vomiting in adults by 4 percent and children by 5 percent. When used for flu prevention, Tamiflu showed a 1 percent increase in the risk of psychiatric events and Tamiflu stopped some people from producing enough of their own antibodies to fight flu infection. Results were similar for Relenza, with no evidence that Relenza reduces the risk of complications or hospitalization.
In an editorial accompanying the review, Cochrane and BMJ editors note that the findings of this review emphasize the need for all data from clinical trials for drugs currently in use to be made available.