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:
- oseltamivir (Tamiflu) drug pamphlet information
- Flu Season 2005-2006: Questions & Answers
- What To Do If You Get The Flu
- Bird Flu What You Need To Know
- Flu Information
- Flu Vaccine Information
- The Cold and Flu Center
Reference: U.S. Food and Drug Administration, Center for Drug Evaluation and Research Tamiflu information page, accessed 11/1/2005.