MEDICATIONS: KEY FACTS ABOUT ANTIVIRAL DRUGS AND INFLUENZA (FLU)

While getting a flu vaccine each year is the best way to protect you from the flu, there also are drugs that can fight against influenza viruses, offering a second line of defense against the flu. These are called "influenza antiviral drugs" and they must be prescribed by a health care professional. These drugs can be used to treat the flu or to prevent infection with flu viruses. 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.

Antiviral drugs are used in different settings and circumstances to treat the flu and to prevent people from getting the flu:

Antiviral drugs are used to help control flu outbreaks in places where a lot of people at high risk of serious flu complications live in close contact with each other, like nursing homes or hospital wards, for example.

Antiviral drugs are used in the community setting to treat people with the flu to reduce severity of symptoms and reduce the number of days that people are sick.

Antiviral drugs are used to prevent the flu:

· For people who have been close to someone with the flu, or

· For people that need protection from the flu but they either don’t get protection after vaccination, or the vaccine is unavailable or they can’t get the vaccine because of allergies, for example.

While most healthy people recover from the flu and don’t have serious complications, some people — such as older people, young children and people with certain health conditions — are at higher risk for serious flu-related complications. It’s especially important that these people are protected from the flu.

Remember, a flu vaccine is the first and best defense against the flu, but antiviral drugs can be an important second line of defense to treat the flu or prevent flu infection.

Two flu antiviral drugs are recommended for use in the United States during the 2007-08 flu season: oseltamavir and zanamavir. Oseltamivir and zanamivir are effective against both influenza A and B viruses.

· Oseltamivir (brand name Tamiflu®) is approved to both treat and prevent flu in people 1 year of age and older.

· Zanamivir (brand name Relenza®) is approved to treat flu in people 7 years and older and to prevent flu in people 5 years 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’s age or medical conditions) and side effects.

Your doctor can help decide whether you should take an antiviral drug this flu season and which one you should use.

For treatment, influenza antiviral drugs should be started within two days after becoming sick and taken for five days. When used this way, these drugs can reduce flu symptoms and shorten the time you are sick by one or two days. They also may make you less contagious to other people.

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 antivirals. He or she may test you for influenza, but testing is not required in order for a physician to recommend influenza antiviral medications for you.

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 percent to 90 percent effective. It’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 person’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. Also, if you are in close contact with someone who is considered at high risk for complications, you may be given antiviral drugs to reduce the chances of catching the flu and passing it on to the high-risk person.

The U.S. Centers for Disease Control and Prevention has provided guidelines for health care professionals on the use of antiviral drugs.

In general, antiviral drugs can be offered to anyone 1 year of age or older who wants to avoid and/or treat the flu. People who are at high risk of serious complications from the flu may benefit most from these drugs.

Antiviral drugs also can be used to prevent influenza among people with weak immune systems who may not be protected after getting a flu vaccine or who haven’t been vaccinated.

Remember, a flu vaccine is the first and best defense against seasonal flu, but antiviral drugs can be an important second line of defense to treat the flu or prevent flu infection.

This information is summarized from Prevention & Control of Influenza - Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2007 Jul 13;56(RR06):1-54 (Also available as PDF, 720K) and focuses on the two licensed influenza antiviral agents recommended for use in the United States during the 2007-08 influenza season: oseltamivir and zanamivir.

There are other antiviral drugs (amantadine and rimantadine), but they are not recommended for use in the United States during the 2007-08 flu season because recent flu viruses are resistant to these drugs. When viruses are resistant to drugs, the drugs don’t work or don’t work as well.