By Kerry Grens
NEW YORK (Reuters Health) - After billions of dollars worldwide have been spent stockpiling the anti-flu drug Tamiflu, two new reports cast doubt on the medication's benefits and say its side effects may have been underestimated.
According to the widely respected Cochrane Collaboration, which analyzes past medical research, Tamiflu shortened the typical flu attack by just one day.
And it didn't seem to reduce the number of infected people who landed in the hospital.
There is "little evidence for the widespread beliefs about its benefits," said Peter Doshi, an author of one of the reports and a researcher at Johns Hopkins University.
Tamiflu, which goes by the chemical name oseltamivir, is an antiviral medication used to treat or prevent influenza.
The United States and other governments have stockpiled the drug to use in case of a flu outbreak, such as the 2009 pandemic.
As part of the Cochrane Collaboration, Doshi and his colleagues were tasked with collecting and analyzing all the available information on Tamiflu.
Unlike most other reviews that rely on reports published in medical journals, the group decided to comb through data from Roche, which manufactures Tamiflu, as well as health regulators in different countries.
Analyzing massive amounts of information from company-funded research, they found that the drug cut the time that people felt flu symptoms from about seven days to six days.
But Tamiflu did not reduce the number of people who ended up being hospitalized, and there was "no evidence it could stop (the spread of the) disease and no evidence it can reduce the risk of complications like pneumonia," said Doshi.
Doshi's team only looked at the randomized controlled trials -- considered the "gold-standard" of medical evidence -- which compared the drug to an inactive placebo. It also focused on people who did not have other health problems.
Another Cochrane review of flu medications, led by Dr. Kay Wang at the University of Oxford, looked at studies of more than 2,300 children up to 12 years old.
Wang's team found that Tamiflu and zanamivir, sold as Relenza, both reduced the time kids had flu symptoms by about one day, and Tamiflu also slightly reduced the chances that kids would develop an ear infection.
To prevent one extra case of flu, 13 kids would need to be treated. And some will get side effects. For instance, for every 17 kids treated with Tamiflu, there will be one more case of vomiting.
Despite the limited benefits, the researchers write that if "economic resources permit, oseltamivir may be considered for the treatment of children aged one to 12 years with influenza infection provided that therapy can be commenced within 48 hours of the start of the illness."
In a statement emailed to Reuters Health by Genentech, which markets Tamiflu for Roche, the company said the drug is safe and effective for the treatment and prevention of influenza.
"Numerous clinical trials and real-life medical experience show Tamiflu is effective in reducing the severity and duration of influenza symptoms as well as specified secondary complications," it said.
Dr. Frederick Hayden, a professor at the University of Virginia Medical School in Charlottesville who has served as an uncompensated advisor to manufacturers of anti-flu drugs since 2008, agreed that the drug is worthwhile.
"I think that there's no doubt that oseltamivir, the generic name, provides real benefit to patients when used in the appropriate populations," he told Reuters Health.
Hayden pointed out that Doshi's review did not incorporate results from observational studies, which monitor what happens in the real world outside of clinical trials.
"Despite the limitations of observational studies, they still can inform public health practice," especially when randomized clinical trials are unavailable, said Dr. Tim Uyeki, an influenza expert in the Influenza Division, at the Centers for Disease Control and Prevention (CDC).
For instance, during the 2009 H1N1 influenza pandemic, observational studies suggested that oseltamivir was effective at reducing severe outcomes among patients in the hospital, particularly when started within the first 48 hours of symptoms, but even up to five days later.
He added that the drug was found to be beneficial for seasonal flu patients too.
The CDC guidelines recommend that antiviral medications should be started immediately for hospitalized patients and people with chronic underlying health problems, pregnant women, elderly persons and young children if they develop signs and symptoms of influenza.
For people without health problems or who are not at a high risk of developing a severe illness, doctors can consider using an antiviral as long as it's within two days of the first signs of illness.
Uyeki said Doshi's study does not change any recommendations for the treatment of influenza, including the use of Tamiflu.
Doshi's group relied on unpublished results from Roche and writes in its report that the company provided only incomplete reports.
The researchers are calling for Roche to share more of its data on Tamiflu, so that independent reviewers can better analyze how well it works.
"We have an incredible source of data that already exists," Doshi told Reuters Health. "The drug company needs to share that data."
Hayden said it was "unfortunate" that Roche had not provided complete reports.
"I fully support that these data need to be shared, both the unpublished and published studies so they can be independently analyzed," he said.
Roche said in its statement that it provided "access to 3200 pages of very detailed information, enabling (the researchers') questions to be answered."
Influenza activity has been low to date, but it is expected to increase in the coming weeks.
Uyeki said that annual influenza vaccination is the best way to prevent the virus, and good hygiene may be helpful as well.
SOURCE: http://bit.ly/y6UwBy and http://bit.ly/y9BkaL Cochrane Database of Systematic Reviews, online January 18, 2012.