The Antiviral Drug Tamiflu Isn't As Effective Against An Influenza Epidemic As Thought: New Study

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The antiviral drug Tamiflu, initially thought to reduce hospitalisations and serious complications from influenza, is not as effective as first thought and actually increases risk of suffering from nausea and vomiting.

A new review raises critical questions about governments stockpiling such drugs for use in a pandemic as they did in 2009. They then used information now known to be incomplete to make the decision to stockpile.

The most recent evidence shows the antiviral drug shortens symptoms of influenza by half a day but there is no evidence to support claims that it reduces admissions to hospital or complications of influenza.

This is according to the updated Cochrane evidence review, published today by The Cochrane Collaboration, the independent, global healthcare research network, and the British journal The BMJ.

Evidence from treatment trials confirms increased risk of suffering from nausea and vomiting. And when Tamiflu was used in prevention trials there was an increased risk of headaches, psychiatric disturbances and renal events.

Although when used as a preventative treatment, the drug can reduce the risk of people suffering symptomatic influenza, it is unproven that it can stop people carrying the influenza virus and spreading it to others.

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.

These trials involved more than 24,000 people.

The evidence also suggests there are insufficient grounds to support the use of Tamiflu in preventing person-to-person spread of influenza.

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 US spent more than $1.3 billion buying a strategic reserve of antivirals, while the UK government spent almost £424 million for a stockpile of about 40 million doses. Australia in 2009 stockpiled 1.9 million doses and New Zealand 750,000.

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.

The worldwide use of Tamiflu and similar drugs has increased dramatically since the outbreak of H1N1 virus (Swine Flu) in April 2009.

However, the original evidence presented to government agencies around the world was incomplete.

Dr David Tovey, Editor-in-Chief, Cochrane, said: “Initially thought to reduce hospitalisations and serious complications from influenza, the review highlights that Tamiflu is not proven to do this, and it also seems to lead to harmful effects that were not fully reported in the original publications. This shows the importance of ensuring that trial data are transparent and accessible.”

Dr Vanessa Jordan, a New Zealand Cochrane Fellow at University of Auckland, says this latest review represents another chapter in a story which reads like a sensationalist script for a Hollywood movie.

“Influenza is the one illness which from time to time may threaten to disrupt our ordered existence,” she says.

“It can affect healthy individuals indiscriminately, the worst epidemics of which have historically decimated populations in centuries past.”

Swine flu hit New Zealand in the winter of 2009, killing 49 people, the majority of which were under the age of 60.

The available data in 2009 suggested that antivirals, such as Tamiflu and Relenza, had potential benefits in reducing complications from influenza and as a result the length of hospital stays.

Based on this the New Zealand government along with governments worldwide purchased and stockpiled 750,000 doses, the majority of which have subsequently been dumped as they have passed their expiration date.

“However, this information was incomplete and full trial evidence on the drug’s effectiveness was suppressed by the manufacturers,” Dr Jordan says.

“This new synthesised evidence confirms what was previously suspected — that there is currently no support for claims that Tamiflu or Relenza reduces admissions to hospital or complications of influenza.

“At most you may get back to work half a day earlier but in trade off for this you may also suffer from some of the side effects such as nausea and vomiting.”

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