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Dr. George Apple of www.Health-Effects.net said, that as Countries scramble to buy Tamiflu, signs are that the highly infectious form of bird flu moving across Russia towards Europe may be sensitive to the older, cheaper drug amantadine (symmetrel).
Countries should be stockpiling amantadine or rimantadine as 'they are cheap and readily available.' Peter Dunnill, Department of Biochemical Engineering at University College London says stockpiling Tamiflu may not be the right route in developing countries.
Sequence data suggest that the Russian virus does not exhibit any of the changes in the M2 ion channel that would make it resistant to amantadine. Early work on the Russian virus also suggests that it is related to the Qinghai virus. Yi Guan of the University of Hong Kong who sequenced the Qinghai strain earlier this year says Qinghai sequence data suggest it is amantadine sensitive. 'It is possible that recent Russian isolates may be sensitive to amantadine as well. Based on my personal observation, it is possible that they are closely related in somehow. Considering the cost of antiviral (Tamiflu), it is another option for developing countries to consider stockpiling amantadine,' he says. But the drug is off-patent so no one is testing it.
Marginal results under ideal experimental conditions do not suggest Tamiflu would be effective under pandemic conditions if used at the recommended dose for the recommended time. Indeed, Tamiflu was used on tigers exposed to H5N1 at the Sri Rahka zoo in Thailand last year. Control of the outbreak with culling and aggressive Tamiflu use failed to save many, if any, of the exposed tigers, which may have been limited to the 147 that died or were euthanized.
At the recommended dosage will produce little benefit. Many countries have stockpiled Tamiflu and more have placed orders. However, the amount of Tamiflu ordered was based on the assumption that a course of 10 pills would be effective for 10 days of prevention or 5 days of treatment. However, this assumption was not supported by in vitro data and now is also not supported by in vivo data.
There may be concerns about using amantadine, however, as over-use of the drug in animals has led to the emergence of wide-spread resistance of H5N1 in Thailand and Vietnam. But resistance can also develop to Tamiflu.
Clearly more work is required to determine the effective dose of Tamiflu. The boxun reports indicate that there are at least 10 distinct strains of H5N1 in China, and 8 can infect humans. Therefore information the effect of Tamiflu on a range of H5N1 variants might be useful.




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