- Hello Jeff - First of all, tamiflu was given to governments
to "STOCKPILE" in the event a pandemic occurs. Why is so much
Tamiflu getting into the environment, so much so that resistant strains
are on the rise? Tamiflu should be used as a last resort.
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- For the most part, people do not need Tamiflu or other
antivirals and doctors should not be prescribing them, especially to other,
normally healthy individuals.
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- We are told that flu shots would cut down on serious
complications of flu, especially in the case of the elderly and infirmed.
So, given the push for flu shots, again, why so many prescriptions for
Tamiflu?
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- Are the governments around the globe really stockpiling
Tamiflu, or are they using it for seasonal flu and for preventive measures
for chickens? No wonder we are seeing virulent, antiviral resistant strains
develop.
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- When the real pandemic hits, there will be nothing in
our medicine arsonal to help prevent deaths.
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- Patty
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- Health Officials Watching Whether Flu Viruses Are Becoming
Resistant To Tamiflu
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- TORONTO -- As flu season
approaches, public health authorities will be keeping an anxious eye on
one family of flu viruses to see if an unwelcome phenomenon that cropped
up last winter will stage a repeat performance.
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- To the surprise and dismay of scientists and governments,
H1N1 viruses that were resistant to Tamiflu suddenly appeared in high numbers
in Northern Europe.
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- Testing elsewhere has since shown viruses resistant to
the key drug - whose generic name is oseltamivir - have spread to North
and South America, the Caribbean, Africa, parts of Asia, Australia and
New Zealand.
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- North American officials say they will quickly test for
resistance once the northern hemisphere flu season begins and H1N1 viruses
start to spread. And in the U.S. at least, authorities are entertaining
the possibility they may have to tweak the advice they give doctors on
which flu drugs to use should - as most expect - the problem recur.
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- "We are thinking about the various sorts of scenarios
that might occur," says Dr. Tony Fiori, who develops antiviral drug
and vaccine policy in the influenza division of the U.S. Centers for Disease
Control in Atlanta, Ga.
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- "It's hard to imagine we'd be at a point of telling
people not to use oseltamivir. We might look at possibilities like pushing
people towards using zanamivir when they can, since there hasn't been resistance
seen to that."
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- Zanamivir is the generic name for GlaxoSmithKline's Relenza,
which, like Tamiflu, belongs to a class of drugs called neuraminidase inhibitors.
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- Both drugs block the ability of flu viruses to spread
from infected cells to healthy ones, making symptoms less severe and speeding
recovery.
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- Tamiflu producer Hoffman-La Roche intends to get into
the surveillance effort, mounting a multi-country study to figure out how
much resistance is out there, whether the resistant viruses cause milder
disease and what happens clinically to people infected with the resistant
viruses who take Tamiflu.
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- "So in a very short space of time we hope to get
a picture on the frequency, if the strain does re-emerge in the northern
hemisphere," says Dr. David Reddy, Roche's pandemic influenza task
force leader.
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- "We don't know what the northern hemisphere will
bring," he said, expressing an optimism not supported by the resistance
pattern seen in H1N1 viruses during the southern hemisphere flu season.
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- Canada too will be testing early so it can inform the
medical community of which kinds of flu viruses are causing the most disease
and whether they are resistant to Tamiflu.
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- But the Public Health Agency of Canada is unlikely to
issue across-the-board recommendations, because the drug still works against
two other types of flu viruses - the other influenza A subtype, H3N2 as
well as influenza B viruses - and because it's unlikely there will be one
single pattern of illness across the entire country.
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- "This season's going to be a little bit more complicated
than previous seasons. And I think one is going to have to . . . at the
local and provincial level take more of a risk-assessment, risk-management
approach based on what strains of flu are circulating," says Dr. John
Spika, acting director general of the centre for immunization and respiratory
infectious diseases.
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- "Are they H1N1 predominantly or are they H3N2? And,
based on the available information, then decide whether or not it is appropriate
to use the oseltamivir or potentially adamantane drugs. And how zanamivir
fits in with that as well."
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- The adamantane drugs are older flu drugs that have their
own resistance problem. In early 2006 both the CDC and the Public Health
Agency told doctors not to use the drugs when it was found over 90 per
cent of H3N2 viruses were resistant to them.
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- As for Tamiflu and Relenza, neither drug has done remarkably
well in the seasonal flu market except in Japan, where Tamiflu is widely
used.
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- So in some ways, the resistance problem isn't likely
to have a huge impact on how doctors treat their patients who contract
influenza - so long as resistance doesn't also emerge in either or both
of H3N2 and influenza B viruses, experts say.
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- "That's what everybody's holding their breath on,"
says Dr. Allison McGeer, an influenza expert at Toronto's Mount Sinai Hospital.
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- "If we see H3N2 resistance at significant levels,
that's the catastrophic bridge."
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- But Roche has sold vast quantities of Tamiflu to governments
and corporations for pandemic influenza stockpiles. Discovering the vulnerability
of the main drug weapon in pandemic arsenals has unsettled governments,
public health officials and flu researchers.
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- "The bigger issue is loss of confidence overall
and how it will shape the stockpiling," says McGeer, who says governments
may be less willing to lay in stockpiles when the next generation of flu
drugs hit the market for fear the Tamiflu phenomenon will repeat itself.
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- It is a fact of nature that bacteria and viruses will
eventually evolve to become resistant to drugs. But research had suggested
that the changes flu viruses would have to undergo to become resistant
to Tamiflu would so weaken them that they would lose the capacity to spread
from person to person.
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- Last winter nature delivered a double whammy: Not only
had resistance emerged - and emerged in places where it was clear misuse
wasn't responsible - but the resistant viruses spread easily.
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- That demolished the theory that resistant viruses were
less biologically fit viruses, at least so far as H1N1 viruses are concerned.
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- "I am really staggered that this H1N1 virus has
been able to spread as it has," says Jennifer McKimm-Breschkin, a
flu antiviral expert at Australia's Commonwealth Scientific and Industrial
Research Organization and a member of the team that developed Relenza.
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- McKimm-Breschkin, who receives no royalties from sales
of the drug, thinks in light of the resistance problem, public health agencies
should be telling doctors to use Relenza this flu season.
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- "The drugs are expensive. So if you have one drug
that you know is effective against all (flu) strains, surely the logical
prescribing pattern is to prescribe that drug."
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- But she thinks officials would be reluctant to issue
that kind of recommendation, because of the lion's share position Tamiflu
holds in most pandemic drug stockpiles.
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- "It is a politically sensitive issue because of
the stockpiling. And governments don't want to alarm people that the stockpiles
may not be useful because the bird flu still remains sensitive," McKimm-Breschkin
says, referring to the dangerous H5N1 strain killing poultry and occasionally
people in parts of Asia and Africa.
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- Other experts say the Tamiflu situation doesn't merit
the same response as the adamantane drug resistance problem did. For one
thing, at least in North America, the Tamiflu resistance rates were lower
last winter - 26 per cent in Canada, and 11 per cent in the U.S. And for
another thing, H1N1 viruses generally cause milder flu than H3N2 viruses.
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- Fiori says there is another important distinction between
the two situations.
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- "I think what makes it somewhat different from the
adamantane situation of a couple of years ago is that we had a good drug
- perhaps even a better drug - in reserve at that point," he says,
referring to Tamiflu.
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- "And we don't at this point. We don't really have
that sort of option here."
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- http://canadianpress.google.com/article/ALeqM5if4uJGxhp784BZ_JVaxVTjnn8KvQ
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- Patricia A. Doyle DVM, PhD
- Bus Admin, Tropical Agricultural Economics
- Univ of West Indies
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- Please visit my "Emerging Diseases" message
board at:
- http://www.emergingdisease.org/phpbb/index.php
- Also my new website:
- http://drpdoyle.tripod.com/
- Zhan le Devlesa tai sastimasa
- Go with God and in Good Health
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