|
E-mail this page to a friend!
Senior Health Alert
Don't Use Amantadine or Rimandatine to Treat Flu,
Warns CDC
Evidence indicates Influenza A viruses in US are
resistant to these drugs
Jan. 15, 2006 The Centers for Disease Control
yesterday issued an urgent health alert warning Americans not to rely on
the antiviral drugs amantadine or rimantadine to treat influenza
infection. The agency says a resistance to the medicines has developed
in much of the US influenza A virus. Amantadine, however, is also used
to treat Parkinsons disease, and should continue to be used for this
treatment.
The discovery increases concern about preparedness
for the bird flu, since the newer antiviral drugs Tamiflu and Relenza
were being conserved for use in incidences of avian flu, if it should
come to the US. Now, the government is recommending these two drugs be
used for the treatment of seasonal flu.
There is some concern a resistance to these drugs
will now begin to develop.
The older, and now ineffective drugs, worked only
against the type A influenza but are less expensive and also available
in generic forms. Tamiflu and Relenza work against type A and type B
influenza and have shown some promise in treating bird flu.
CDC officials held an unusual Saturday news
conference to release the warning.
Following is the CDC statement:
While the primary strategy for preventing
complications of influenza infections is annual vaccination, antiviral
medications with activity against influenza viruses can be effective for
the prophylaxis and treatment of influenza. Two classes of antivirals
are currently availablethe M2 ion channel inhibitors (i.e., the two
adamantanes amantadine and rimantadine) and the neuraminidase inhibitors
(i.e., oseltamivir and zanamivir).
The neuraminidase inhibitors are effective for the
treatment and prophylaxis of influenza A and B, while the adamantanes
are only active against influenza A viruses. This alert provides new
information about the resistance of influenza viruses currently
circulating in the United States to the adamantanes, and it makes an
interim recommendation that these drugs not be used during the 200506
influenza season. Amantadine is also used to treat the symptoms of
Parkinsons disease, and should continue to be used for this indication.
Viral resistance to adamantanes can emerge rapidly
during treatment because a single point mutation at amino acid positions
26, 27, 30, 31, or 34 of the M2 protein can confer cross-resistance to
both amantadine and rimantadine.
The transmissibility of adamantane-resistant
viruses is not impaired by any of these amino acid changes. A recent
report on the global prevalence of adamantane-resistant influenza
viruses showed a significant increase (from 1.9% to 12.3%) in drug
resistance over the past 3 years. In the United States, the frequency of
drug resistance increased from 1.9% in 2004 to 14.5% during the first 6
months of the 200405 influenza season.
For the 200506 season, 120 influenza A (H3N2)
viruses isolated from patients in 23 states have been tested at CDC
through January 12, 2006; 109 of the isolates (91%) contain an amino
acid change at position 31 of the M2 protein, which confers resistance
to amantadine and rimantadine. Three influenza A(H1N1) viruses have been
tested and demonstrated susceptibility to these drugs. All influenza
viruses from the United States that have been screened for antiviral
resistance at CDC have demonstrated susceptibility to the neuraminidase
inhibitors.
On the basis of available antiviral testing
results, CDC is providing an interim recommendation that neither
amantadine nor rimandatine be used for the treatment or prophylaxis of
influenza A in the United States for the remainder of the 200506
influenza season.
During this period, oseltamivir or zanamivir should
be selected if an antiviral medication is used for the treatment and
prophylaxis of influenza. Testing of influenza isolates for resistance
to antivirals will continue throughout the 200506 influenza season, and
recommendations will be updated as needed. Annual influenza vaccination
remains the primary means of preventing morbidity and mortality
associated with influenza.
Additional information about the prevention and
control of influenza is available at
www.cdc.gov/flu. Specific information regarding the use of the
neuraminidase inhibitors is available at
www.cdc.gov/flu/protect/antiviral. These websites will be updated as
new information becomes available.
Click here to Search SeniorJournal.com for more on
this subject
Click to More Senior News on the
Front Page
Copyright: SeniorJournal.com |
