The antiviral drug Tamiflu (oseltamivir) shortens symptoms of influenza by half a day, but evidence does not support claims that it reduces hospitalizations or complications of influenza, according to a data review.
The review was published April 10 on the website of the British Medical Journal by The Cochrane Collaboration, an independent, global healthcare research network. Evidence from treatment trials confirms increased risk of suffering from nausea and vomiting. When Tamiflu was used in prevention trials, risks increased for headaches, psychiatric disturbances and renal events.
Although the drug can reduce the risk of symptomatic influenza when used as a preventive treatment, its ability to stop people from carrying and spreading the influenza virus is unproven.
The latest updated Cochrane Review, Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children, is based on full internal reports of 20 Tamiflu (oseltamivir) and 26 Relenza (zanamivir) trials. The findings of these trials, which involved more than 24,000 people, challenge the historical assumption that neuraminidase inhibitors are effective in combating influenza. The evidence also suggests there are insufficient grounds to support the use of Tamiflu in preventing person-to-person spread of influenza.
These findings raise questions about the most effective way to support drug regulation and public health policy decision-making. Claims about the effectiveness of Tamiflu against complications were a key factor in decisions made by governments around the world to stockpile these drugs in case of a pandemic. The U.S. has spent more than $1.3 billion buying a strategic reserve of antivirals, according to a Cochrane news release.
In 2009, a lack of access to available trial data hampered the efforts of the Cochrane researchers to verify the safety and effectiveness of Tamiflu, and led to questions over decisions to stockpile the drug while the risks and benefits remained uncertain, according to the news release. In the wake of the new findings, the BMJ and Cochrane say government and health policymakers around the world should question recommendations to stockpile Tamiflu.
Compared with a placebo, taking Tamiflu led to a quicker alleviation of influenza-like symptoms of a little more than half a day (from 7 days to 6.3 days) in adults, but the effect in children was more uncertain. There was no evidence of a reduction in hospitalizations or serious influenza complications, confirmed pneumonia, bronchitis, sinusitis or ear infection in either adults or children.
Tamiflu also increased the risk of nausea and vomiting in adults by around 4% and in children by 5%. There was a reported increased risk of psychiatric events of around 1% when Tamiflu was used to prevent influenza. Evidence also suggests Tamiflu prevented some people from producing sufficient numbers of their own antibodies to fight infection.
The worldwide use of Tamiflu has increased dramatically since the outbreak of H1N1 virus in April 2009. It was initially believed the drug would reduce hospital admissions and complications of influenza, such as pneumonia, during influenza pandemics. However, the original evidence presented to government agencies around the world was incomplete. The Cochrane Review has benefited from access to more complete reports of the original research, now made available by the manufacturers, Roche and GlaxoSmithKline.
Study (PDF): http://bit.ly/Q6Be0A