[Pharmwaste] Researchers warn about overprescribing Tamiflu

[Tenace, Laurie]

Researchers warn about overprescribing Tamiflu
http://sciam.com/article.cfm?alias=researchers-warn-about-ov&chanID=sa003&mod
src=reuters 

 Sewage systems do not break down Tamiflu, which means the main weapon
against bird flu could seep into natural waters and make certain viruses
resistant to the drug during a pandemic, Swedish researchers said on
Wednesday.

Because of this, doctors should take care to not overprescribe Roche Holding
AG's market-leading antiviral drug, they said in a study published in the
Public Library of Science.

"Antiviral medicines such as Tamiflu must be used with care and only when the
medical situation justifies it," Bjorn Olsen, a researcher at Uppsala
University and the University of Kalmar said in a statement.

"Otherwise there is a risk that they will be ineffective when most needed,
such as during the next influenza pandemic."

Roche, which the researchers said donated the drug for their study, said it
was unlikely such resistance would arise.

"In the highly unlikely event that such resistance was generated, this must
be balanced against the fact that influenza viruses with the associated
mutational changes have been shown to have lower transmissibility," the
company said.

Tamiflu, known generically as oseltamivir, was having lackluster sales as a
drug to prevent and treat seasonal flu until it was the first treatment to
show real efficacy in helping people with bird flu.

Health experts agree that a pandemic of something is inevitable. They cannot
specify the disease, but the H5N1 avian flu virus currently wiping out flocks
from Indonesia to Africa and parts of Europe is the main suspect.

It rarely infects people but has killed 201 out of 329 people sickened since
the virus re-emerged in Hong Kong in 2003, according to the World Health
Organisation.

In their study, the Swedish team said low levels of oseltamivir, the active
substance in Tamiflu, passed virtually unchanged through basic sewage
treatment processes.

People had long suspected that Tamiflu would not break apart during such
treatment but this is the first time researchers have actually shown this,
the researchers said.

In certain countries, the level discharged through these outlets may be so
high that influenza viruses in nature could develop resistance to Tamiflu,
they said.

"Use of Tamiflu is low in most countries, but there are some exceptions such
as Japan where a third of all influenza patients are treated with Tamiflu,"
Jerker Fick, a researcher at Umea University who led the study, said in a
statement.

The biggest threat is from waterfowl such as ducks that often forage near
sewage outlets, Fick said. These birds could encounter oseltamivir in high
enough concentrations to develop resistance to flu viruses they carry, the
researchers said.

In turn, the viruses could combine with other viruses that make humans sick
and mutate into strains resistant to currently available antiviral drugs like
Tamiflu, they added.


Laurie J. Tenace
Environmental Specialist
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us 

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