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Combination of drugs should be stockpiled to fight flu pandemic, say experts

7 February 2007

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A combination of antiviral drugs should be stockpiled for use in an influenza pandemic, say researchers in this week’s BMJ (Volume 334 pp 293-4).

We currently have two classes of drugs that are effective against influenza viruses: the ion channel inhibitors (amantadine and rimantadine) and the neuraminidase inhibitors (oseltamivir and zanamivir).

Although ion channel inhibitors are effective against several strains of influenza viruses, they are not being widely stockpiled for a future flu pandemic because they cause unacceptable side effects and their use is associated with a rapid emergence of resistance.

But researchers argue that combining the two types of drugs may reduce side effects and the risk of resistance, and could play an important role in our armoury against a future flu pandemic.

In laboratory tests, the combination of ion channel and neuraminidase inhibitors reduced the emergence of resistance and even prevented the emergence of resistant strains of the highly pathogenic avian influenza H5N1 virus.

Ion channel inhibitors are also considerably cheaper than neuraminidase inhibitors, so the cost implications of maintaining stocks of both types of drug are therefore modest, say the authors. These drugs are also chemically stable, giving them a long shelf life.

The World Health Organisation (WHO) recently recommended combined use of ion channel and neuraminidase inhibitors against the H5N1 strain, but this recommendation was deemed weak because of a lack of good evidence. Adequately sized trials of such combinations are therefore urgently needed, they added.

Several countries, including the US, the UK and Greece, are already stockpiling ion channel inhibitors. Other countries should consider following suit, say the authors. Failure to stockpile both types of antiviral drugs could prove costly.

An accompanying editorial discusses new guidelines on the clinical management of pandemic flu and says that the United Kingdom is well advanced in its preparations for a flu pandemic.