Tamiflu for Bird Flu?
Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: Jay W. Marks, MD
Media reports about the supply of the drug Tamiflu
abound as fears of a global bird flu pandemic mount. Tamiflu is the brand name for a drug known as
oseltamivir, one of a class of antiviral drugs that
can help reduce the severity of flu symptoms. Of the four antiviral medications
that are available to treat an infection with the flu virus (oseltamivir (Tamiflu), zanamivir (Relenza),
amantadine (Symmetrel), and rimantadine (Flumadine)), Tamiflu has been most
often prescribed by doctors.
Tamiflu is not the same thing as a influenza vaccination ("flu
shot"), nor can it replace the flu shot. Rather, by blocking the action of an
enzyme called neuraminidase that helps cells infected with the influenza virus
spread the infection to healthy cells, Tamiflu reduces the severity of symptoms and the
duration of an influenza virus infection.
Tamiflu has been approved by the U.S. Food and Drug
Administration (FDA) for
treating influenza infection and for
reducing the chances of contracting the flu in both adults and children over age one who may
be at risk for getting the flu due to exposure to an infected person or in the
presence of a community outbreak of the flu.
Studies about the effectiveness of Tamiflu as a
preventive measure showed that in healthy adults, there was a significantly
lower incidence of influenza among those who took the drug, with
1.3% of healthy adults who took Tamiflu eventually developing the flu, while
4.8% of those who received a placebo became ill with
influenza. However, the cost-effectiveness of Tamiflu as a preventive measure
must be considered, since these results indicate that 29 people must be treated with Tamiflu in order to
prevent one infection.
Vaccination (the "flu shot"), therefore, should remain
the first line of defense against the flu for healthy adults. Vaccination is
cheaper, and research has shown that when there is a good match between the
virus strains chosen for the vaccine and those in circulation, the vaccine
prevents influenza illness in approximately 70%--90% of healthy adults under 65
years of age. Treatment with Tamiflu may be considered in high-risk populations
or after an incompletely effective flu vaccination (when there is not a good
match between the viruses used to prepare the vaccine and viruses in
circulation).
Tamiflu also has the advantage of offering both
prevention and treatment for the flu in the case of an outbreak of a new strain
of flu virus,
when there has been insufficient time for preparation of a vaccine directed
against the new strain of flu virus. Of the antiviral drugs available to treat
the flu, only oseltamivir (Tamiflu) and zanamivir are active against all strains
of influenza virus. Zanamivir, unlike Tamiflu, has only been approved for the
treatment, and not the prevention, of influenza.
Tamiflu must be taken within 48 hours after flu symptoms
appear in order to be effective in reducing the severity of the flu. As with any
drug, certain precautions are necessary when taking Tamiflu. Its safety and
effectiveness have not been determined in people with chronic heart or lung
disease, kidney failure, or people with high-risk underlying medical conditions.
. It has also not been determined if Tamiflu is safe for use by pregnant women.
Tamiflu has not been approved for use in infants under one year of age, and the
safety of repeated courses of Tamiflu has not been determined. Side effects may
occur when taking Tamiflu. The most common reported side effects of Tamiflu are
nausea and vomiting.
If you believe you are getting the flu, talk to your
doctor as soon as symptoms appear. He or she can help you decide if treatment
with Tamiflu or another antiviral medication may be
appropriate.
For more, please read the following articles:
Reference: U.S. Food
and Drug Administration, Center for Drug
Evaluation and Research Tamiflu information page, accessed 11/1/2005.
Last Editorial Review: 1/13/2006
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