Bird flu: Lancet study cautious over drug-of-choice Tamiflu

http://news.yahoo.com/s/afp/20060119/hl_afp/healthflutamiflustudy_060119000723
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PARIS (AFP) - Medical reviewers warned sternly against over-relying on
the drug Tamiflu in global preparations to prevent an influenza
pandemic triggered by bird flu.
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In a paper published online by the British journal The Lancet, the
experts say they see no evidence that the top-selling drug worked
against H5N1 avian influenza and fear the treatment could be of limited
use if the H5N1 virus ever mutates into a feared pandemic form.

Tamiflu -- lab name oseltamivir -- and Relenza (zanamivir) are drugs
designed to ease the symptoms of influenza and reduce the duration of
the sickness. They are not cures.

Even so, health watchdogs believe that they can play a vital role by
braking a pandemic if ever H5N1, at present a pathogen transmitted from
poultry to humans, mutates into a form that makes it highly infectious
among people.

By swiftly administering these so-called neuraminidase inhibitor drugs
in a place where the novel virus is detected, doctors could halt or at
least slow its spread, according to their thinking.

Driven by this faith, governments around the world are rushing to build
up reserves of these medications, especially Tamiflu, which is taken as
a simple tablet and is thus preferred over Relenza, which requires an
inhaler.

But the Lancet paper cautions against placing excessive faith in these
stockpiles.

It says the drugs are useful in some important ways but should only be
placed alongside simple low-cost measures, such as isolating infected
patients and encouraging the public to don face masks and wash their
hands, in the arsenal of anti-pandemic weapons.

The authors, led by Tom Jefferson of Cochrane Vaccines Field, a
Rome-based organisation, looked at scores of previously-published
studies into Tamiflu and Relenza, as well as two veteran flu drugs,
amantadine and rimantidine, that are in a different pharmaceutical
class.

Their goal was to assess the overall effectiveness of these drugs
against seasonal (that is, non-pandemic) influenza, and their safety.

Tamiflu and Relenza did indeed ease symptoms and reduced the sickness
time provided a patient took them within 48 hours of feeling unwell.
They also helped prevent pneumonia and bronchitis, which often result
from flu, according to this review.

But neither drug worked against asymptomatic cases -- people who
carried the flu virus but did not feel sick, and thus may have been
able to infect others.

In addition, the drugs significantly decreased the amount of nasal
secretion of the virus, but they did not stop it.

Sneezing, as well as coughing, are flu's best ways of getting about,
for the virus is passed through airborne droplets and through
handshakes, door handles, elevator buttons, computer keys and other
contacts.

The secretion finding is important, for a review led by the World
Health Organisation (WHO) found that people infected with H5N1 flu
sneezed out titanic volumes of virus -- up to 10 times more than
ordinary, seasonal flu.

The Jefferson team also looked at the somewhat sketchy accounts of the
use of Tamiflu against three strains of bird flu: the H5N1, H7N7 and
H7N3.

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They found no evidence that Tamiflu reduced the death rate in Asia from
H5N1, although this could admittedly be because doctors were
administering it too late to make much of a difference.
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And, in a number of cases in Japan and Vietnam, they found a relatively
high rate (16 percent) of resistance to Tamiflu.

"We could find no credible evidence of the effects of neuraminidase
inhibitors on avian influenza," the paper says.

Tamiflu and Relenza "might have a role" to play in addressing symptoms
and complications in a flu outbreak, says the paper.

But these drugs have only a low effectiveness for controlling a flu
outbreak, either of a seasonal kind or a future pandemic, and the
public should not be overconfident.

"(Neuraminidase inhibitors) should only be used in a serious epidemic
or pandemic alongside other public-health measures such as use of
masks, gowns, gloves, quarantine and handwashing," Jefferson said.

Both amantadine and rimantidine are ruled out for any kind of flu
control, because they are ineffective and cause side effects, the paper
adds.
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Regards,

John M. Drake

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