No Evidence Tamiflu Can Prevent Complications in Flu Victims

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A new study that evaluated data on Tamiflu found no evidence that the popular flu medication can prevent otherwise healthy people who have flu from suffering complications such as pneumonia. The study investigators reviewed 20 trials of Tamiflu (oseltamivir) to arrive at their conclusion.

Tamiflu is in the drug class called neuraminidase inhibitors, which also includes zanamivir. According to Roche, Tamiflu is the most frequently prescribed flu medication for treatment of influenza, and it is approved for adults and children aged 1 year and older. To realize any benefits from the drug, individuals must take it within 48 hours from the first appearance of symptoms.

The authors of the new study, which was published in the British Journal of Medicine, report that Roche, the manufacturer of Tamiflu, has withheld data from trials on their product, which has prevented scientists from evaluating how well the anti-flu drug works. According to an article in The Guardian, the reviewers did not have access to eight trials because they had not been published, and Roche offered them “under conditions we thought unacceptable, and what was offered to us was insufficient to analyze properly.”

Because the study’s reviewers were not allowed to see the full results of the eight trials, they are skeptical about the reliability of previous evidence on the effects of Tamiflu and other drugs in the same class.

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In their review, the researchers analyzed 20 published trials, including four that focused on prevention, 12 on treatment, and four on postexposure prevention. All the studies were randomized, placebo-controlled trials of neuraminidase inhibitors administered to otherwise healthy adults exposed to naturally occurring flu.

Results of the prevention studies showed that neuraminidase inhibitors had no effect against flu-like illness or asymptomatic flu. Other evidence suggested that oseltamivir did not reduce flu-related lower respiratory tract complications. The researchers did find evidence that oseltamivir may shorten the time a person suffers with flu symptoms by a day or so, and that the drug can also cause nausea.

In a second review, which was conducted at Birmingham University in England, the researchers analyzed observational studies provided by Roche. These trials evaluated the effects of the drugs on people but did not use a comparison group of individuals who did not take them. One of the reviewers, Nick Freemantle, noted in The Guardian that he observed “very little evidence to support the widespread use of oseltamivir in the otherwise healthy population who are developing signs of influenza-like illness.”

The conclusion of the British Medical Journal study is that neuraminidase inhibitors, including Tamiflu, are modestly effective against flu symptoms in otherwise healthy adults. It also found a “paucity of good data” to support claims that oseltamivir can prevent complications from flu. Roche reports that its data are solid and has offered to put summaries of all Tamiflu trial data on a password-protected website.

SOURCES:
Jefferson T et al. British Medical Journal 2009; 339:b5106 online
The Guardian London, Dec. 10, 2009

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