Roche’s Tamiflu (oseltamivir) and GlaxoSmithKline’s Relenza (zanamivir), two drugs which are prescribed for the prevention and treatment of influenza in adults and children, have been touted as effective drugs in reducing hospital admissions and flu complications. But now, researchers report that there isn’t substantial evidence to make these claims ring true.
In the latest Cochrane Review by the Cochrane Collaboration, an independent, global healthcare research network, published in the British medical journal BMJ, researchers say there is no solid evidence to support such claims. The latest updated Cochrane Review involved full internal reports of 20 Tamiflu and 26 Relenza trials, involving more than 24,000 people.
According to the researchers, the worldwide use of Tamiflu has increased dramatically since the outbreak of H1N1 virus, known as Swine Flu, in April 2009.
Increased Risk of Side Effects
Tamiflu shortens symptoms of influenza by half a day, but there is no good evidence to support claims that it reduces admissions to hospital or complications of influenza, said the researchers. In fact, they noted that evidence from treatment trials confirms increased risk of suffering from nausea and vomiting.
What’s more, when Tamiflu was used in prevention trials, there was an increased risk of headaches, psychiatric disturbances, and renal events, the researchers said.
Emphasizing that when Tamiflu is used as a preventative treatment, the drug can reduce the risk of people suffering symptomatic influenza, the researchers said that there is no proof that it can stop people from carrying the influenza virus and spreading it to others.
In the study, compared with a placebo, taking Tamiflu led to a quicker alleviation of influenza-like symptoms of just 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, such as confirmed pneumonia, bronchitis, sinusitis, or ear infection in either adults or children, according to the study.
Tamiflu also increased the risk of nausea and vomiting in adults by around 4 percent and in children by 5 percent. There was also a reported increased risk of psychiatric events of around 1 percent when Tamiflu was used to prevent influenza.
Evidence also suggests that Tamiflu prevented some people from producing sufficient numbers of their own antibodies to fight infection, according to the study.
Manufacturers Defend Flu Drugs’ Effectiveness
GlaxoSmithKline, manufacturer of Relenza, provided Healthline with the following comment regarding the study’s findings: “We were committed to giving the Cochrane team access to the data they required from the outset and we are pleased to have been able to support their research. We’re also glad our commitments to transparency have been recognized by the team. We continue to believe the data from Relenza’s clinical trial program support its effectiveness against flu and that when used appropriately, in the right patient, it can reduce duration of flu symptoms. Relenza remains an important option for health professionals who are responsible for deciding when these medicines should be used.”
Roche, makers of Tamiflu, also provided Healthline with a statement, in which they challenged the study's findings: “We fundamentally disagree with the overall conclusions of the Cochrane Acute Respiratory Infection Group’s (ARI) report on Tamiflu (oseltamivir phosphate). We firmly stand by the quality and integrity of our data, reflected in decisions reached by 100 regulators across the world, including the U.S. Food and Drug Administration who have approved Tamiflu to reduce the severity and duration of flu symptoms.”
The statement went on to say, “As we’ve witnessed this flu season in the United States, influenza is a serious viral infection, which can result in death, even among otherwise healthy people. Cochrane’s report fails to take into account the totality of data available for Tamiflu, including only 20 out of 77 clinical trials available to them and excluding real-world data from observational trials.”
Should U.S. Continue to Stockpile Flu Drugs?
Emphasizing that 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 researchers pointed out that the U.S. has spent more than $1.3 billion buying a strategic reserve of antivirals.
In 2009, the Cochrane researchers attempted to verify the safety and effectiveness of Tamiflu, but they said they were hampered by a lack of access to available trial data, raising questions over decisions to stockpile the drug while the risks and benefits remained uncertain.
Now, BMJ and Cochrane are urging government and health policy decision makers worldwide to reconsider whether they would make the recommendations today to decide to stockpile Tamiflu. The researchers also recommend that guidance on the use of both neuraminidase inhibitors (oseltamivir and zanamivir) in the prevention or treatment of influenza should be revised to take account of the evidence of small benefit and increased risk of harms.
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