Information courtesy of the Centers for Disease and Control and Prevention

Antiviral Drugs

Antiviral drugs are prescription medicines (pills, liquid or an inhaler) with activity against influenza viruses, including H1N1 influenza viruses. Antiviral drugs can be used to treat H1N1 or to prevent infection with H1N1 viruses. These medications must be prescribed by a health care professional. Influenza antiviral drugs only work against influenza viruses.

There are four influenza antiviral drugs approved for use in the United States (oseltamivir, zanamivir, amantadine and rimantadine). The H1N1 virus is resistant to amantadine and rimantadine; therefore, these drugs will not work against H1N1. Laboratory testing on the H1N1 virus so far indicates that they are susceptible (sensitive) to oseltamivir and zanamivir.

Update: On September 22, 2009 CDC updated its recommendations for the use of influenza antiviral medicines to provide additional guidance for clinicians in prescribing antiviral medicines for treatment and prevention (chemoprophylaxis) of influenza during the 2009-2010 flu season. These recommendations are intended to help clinicians prioritize use of antiviral drugs for treatment and prevention of influenza. As in earlier antiviral recommendations posted on May 6, 2009 and updated on September 8, 2009, the priority for use of antiviral medications this season continues to be in people with more severe illness, such as people hospitalized with influenza, and people at increased risk of influenza-related complications. This document has been updated to provide additional clarification on several issues, including the increased risk for complications in young children, particularly children younger than 2 years of age.

As with any medical decision making, clinical judgment is an essential factor in making decisions about treatment with antiviral medications.

Benefits of Antiviral Drugs

Treatment: If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious influenza complications. For treatment, antiviral drugs work best if started as soon after getting sick as possible, and might not work if started more than 48 hours after illness starts.

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 H1N1. When used to prevent the flu, antiviral drugs are about 70% to 90% effective. When used for prevention, the number of days that they should be used will vary depending on a person’s particular situation.

CDC Recommendation

CDC recommends the use of oseltamivir or zanamivir for the treatment and/or prevention of infection with H1N1.

* 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.

Update: For antiviral chemoprophylaxis of H1N1 influenza virus infection, either oseltamivir or zanamivir are recommended. Currently, circulating 2009 H1N1 viruses are susceptible to oseltamivir and zanamivir, but resistant to amantadine.

Clinicians should consider treating any person with confirmed or suspected H1N1 with an antiviral drug. Visit the CDC for specific recommendations.

Learn more about Antiviral Drugs and the treatment of H1N1 by visiting the CDC online.

Influenza

What are the symptoms of seasonal influenza or 2009 H1N1 influenza?

The symptoms of seasonal and 2009 H1N1 influenza include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people may also have vomiting and diarrhea. Some people may be infected with the flu, including 2009 H1N1, and have respiratory symptoms without a fever.

Who is at higher risk of influenza related complications?

Groups at higher risk for influenza related complications from 2009 H1N1 are similar to those at higher risk for seasonal influenza complications and include: children younger than 5 years old (risk is highest in children younger than 2 years old); adults 65 years of age and older, pregnant women, people of any age with certain chronic medical conditions (for example, asthma, diabetes, lung disease, people with weakened immune systems, etc.) and people younger than 19 years of age who are receiving long-term aspirin therapy. Children 2-4 years of age are at somewhat higher risk of hospitalization from 2009 H1N1 and seasonal flu compared to older children, and for seasonal flu and have high rates of outpatient and emergency department visits for influenza.

Antiviral Drugs and Flu Vaccine

Can antiviral drugs be helpful for people unable to take the flu vaccine?

Yes. CDC and ACIP recommend use of antiviral drugs for people allergic to eggs (which can cause them to have an allergic reaction to the vaccine) or for people who previously have encountered complications from Guillain-Barre syndrome (GBS) associated with influenza vaccination. In addition, taking antiviral drugs may be recommended among persons that may not have a good immune response to the flu vaccine.

Should people use antiviral drugs before or after receiving the live attenuated influenza vaccine (LAIV) called FluMist®?

LAIV is one of two types of flu vaccine. It is given as a nasal spray and contains weakened, live virus. Flu antiviral drugs taken from 48 hours before through 2 weeks after getting LAIV can lower or prevent the vaccinated person from responding to the vaccine and the person may not get immune protection from the vaccine.

Antiviral drugs can be taken with the inactivated (i.e. killed) flu vaccine.