Key Facts About Antiviral Drugs and Influenza (Flu)

Background

While getting a flu vaccine each year is the best way to protect you from flu, there also are drugs that can fight against influenza viruses, offering a second line of defense against the flu. These are called a??influenza antiviral drugs.a?? Antiviral drugs are prescription medicines (pills, liquid or an inhaled powder), not a vaccine, that fight against the flu by keeping flu viruses from reproducing in your body.

If you get sick with the flu, including the new 2009 H1N1 virus, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. Antiviral drugs are not sold over-the-counter and are different from antibiotics.

During the ongoing 2009 H1N1 pandemic, the priority use for antiviral drugs will be for people who are very sick (hospitalized) or people who are sick with the flu and who are at increased risk of serious flu complications, such as pregnant women, young children, those with chronic health conditions, and people age 65 years and older. For treatment, antiviral drugs work best if started within the first 2 days of symptoms.

During the current pandemic, the priority use for influenza antiviral drugs is to treat severe influenza illness (for example hospitalized patients) and people who are sick who have a condition that places them at high risk for serious flu-related complications.? Influenza antiviral drugs only work against influenza viruses -- they will not help treat or prevent symptoms caused by infection from other viruses that can cause symptoms similar to the flu. While most healthy people recover from influenza virus infections and dona??t have serious complications, some people are at higher risk for serious flu-related complications. Ita??s especially important that these people are protected from the flu. Please see Flu Symptoms & Severity for a full list of those at high risk of seasonal flu-related complications.

Antiviral Drugs

There are four flu antiviral drugs approved for use in the United States.* The four antiviral drugs are:

• Oseltamivir (brand name Tamiflu®) is approved to both treat and prevent influenza A and B virus infection in people one year of age and older.
• Zanamivir (brand name Relenza®) is approved to treat influenza A and B virus infection in people 7 years and older and to prevent influenza A and B virus infection in people 5 years and older.
• Amantadine (Symmetrel®, generic) is approved to treat and prevent only influenza A viruses in people older than 1 year.
• Rimantadine (Flumadine®, generic) is approved to prevent only influenza A virus infection among people older than 1 year. It is approved to treat only influenza A virus infections in people 13 and older.

Antiviral drugs differ in terms of who can take them, how they are given, their dose (which can vary depending on a person"e;s age or medical conditions), and side effects.

For more information, see "Information for Health Care Professionals: Using Antiviral Agents for Seasonal Influenza" or consult the package insert for each drug. Your doctor can help decide whether you should take an antiviral drug this flu season and which one you should use.

Use of Antiviral Drugs for Treatment

For treatment, influenza antiviral drugs work best when started within 2 days after becoming sick, however hospitalized patients might benefit from treatment started more than 48 hours after symptoms begin. When used this way, these drugs can reduce flu symptoms and shorten the time you are sick by 1 or 2 days.

If you become sick with flu-like symptoms this season, your doctor will consider the likelihood of influenza being the cause of your illness, the number of days you have been sick, side effects of the medication, etc. before making a recommendation about using antiviral drugs. He or she may test you for influenza, but testing is not required in order for a health care provider to recommend influenza antiviral medications for you.

Use of Antiviral Drugs for Prevention

Influenza antiviral drugs also can be used to prevent influenza when they are given to a person who is not ill, but who has been or may be near a person with influenza. When used to prevent the flu, antiviral drugs are about 70% to 90% effective. Ita??s important to remember that flu antiviral drugs are not a substitute for getting a flu vaccine. When used for prevention, the number of days that they should be used will vary depending on a persona??s particular situation.

In some instances, your doctor may choose to prescribe antiviral drugs to you as a preventive measure, especially if you are at high risk for serious flu complications and either did not get the flu vaccine or may still be at risk of illness even after vaccination.

Who Should Get Antiviral Drugs?

People who are at high risk of serious complications from the flu may benefit most from these drugs. CDC has provided interim guidance on the use of antiviral drugs for the 2009-2010 influenza season.