Influenza (Flu) Antiviral Drugs and Related Information

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New Information

Update: 10/30/2009 Peramivir IV Questions and Answers for Health Care Providers Information

Update: 10/23/2009 Information for Healthcare Professionals - Mandatory Adverse Event Reporting for Emergency Use of Peramivir Under EUA. Information

Update: 10/23/2009 Peramivir Letter for Emergency Use Authorization Information

Update: 10/02/2009 Information for Healthcare Professionals - Authorization of Use of Expired Tamiflu for Oral Suspension. Information



The term "influenza" refers to illness caused by influenza virus. This is commonly also called "flu", but many different illnesses cause "flu-like" systemic and respiratory symptoms such as fever, chills, aches and pains, cough, and sore throat. In addition, influenza itself can cause many different illness patterns, ranging from mild common cold symptoms to typical "flu" to life-threatening pneumonia and other complications, including secondary bacterial infections.

The main focus of this webpage is on the drugs approved by FDA for the treatment and prevention of influenza.  Because vaccination is the primary means of preventing and controlling influenza, links are also provided to information pertaining to vaccines.  For additional updates and comprehensive information from FDA, please go to the 2009 H1N1 Flu Virus (Swine Flu) Information page.

Information provided on this web site may change frequently, and should not be used as a substitute for individual evaluation by a health care provider, or as the primary means of diagnosing influenza or determining treatment.


Influenza Vaccine Information

Influenza vaccine is the principal method of preventing and controlling influenza. The following links provide information on general uses of vaccines and on current supply issues.

    • Seasonal Flu Vaccine. Information from Center for Biologics Evaluation and Research (CBER) about 2009 - 2010 Seasonal Influenza Vaccine.
    • 2009 H1N1 Influenza Vaccine. Information from Center for Biologics Evaluation and Research (CBER) about 2009 H1N1 Influenza Vaccine.
    • Seasonal Flu. Comprehensive flu information for consumers and healthcare professionals from the Centers for Disease Control and Prevention (CDC).
    • Influenza Vaccine: What you need to know.   Consumer pamphlet from the CDC containing basic vaccine questions and answers.

Use of Antiviral Medications to Treat Influenza

Uncomplicated influenza gets better with or without treatment, but may cause substantial discomfort and limitation of activity before getting better. Complications of influenza can include bacterial infections, viral pneumonia, and cardiac and other organ system abnormalities. People with chronic medical conditions may be at increased risk for complications when they get influenza. Many other diseases, including serious infections such as rapidly progressive bloodstream infections, may start with symptoms that resemble influenza and may need to be considered in treatment decisions. Rapid laboratory tests can help in detecting influenza but a negative test does not rule out the possibility of an influenza infection in a specific patient, and positive tests do not exclude the possibility of other illnesses or take the place of clinical evaluation.

Many people with uncomplicated influenza use over-the-counter medicines to help lessen their symptoms, in addition to staying home and getting adequate rest and fluids. Antiviral drugs available by prescription can also help to reduce the time it takes for symptoms to improve in uncomplicated illness caused by influenza virus, and are sometimes used in selected situations to reduce the chance of influenza illness if people are exposed to influenza.  The level of interest in antiviral drugs for influenza has been increased by recent influenza outbreaks and discussions of public health preparedness.

Complications of influenza, and other illnesses that resemble influenza, may require different treatment and may need urgent medical attention. Use of antiviral drugs does not eliminate the risk of complications, and some complications (as well as other medical conditions that could be confused with influenza) can be life-threatening. There have been some reports of people with other types of infections that got worse if they were treated only for influenza and not for the other infections, see Public Health Advisory: Safe and Appropriate Use of Influenza Drugs, for additional information. In addition, influenza viruses can become resistant to specific anti-influenza antiviral drugs, and all of these drugs have side effects. Therefore, if you have new symptoms during treatment, or your symptoms persist or get worse during treatment, you should see your health care professional.

Outbreaks of influenza occur every year and typically reach epidemic levels during some part of the season.  If a new variety of influenza starts to be transmitted rapidly between people, it can cause extremely widespread illness known as a pandemic. Depending on the strain of influenza causing a pandemic, antiviral drugs may have varying levels of usefulness.  The government has been stockpiling antiviral drugs, and developing recommendations about their use, as part of pandemic preparedness efforts.

Over the last several years, there has been a lot of concern about whether the next pandemic could arise from “bird flu†infection, a term used to refer to a number of influenza viruses that occur in birds and can sometimes cause infections in people.  Starting in early 2009, another strain of influenza emerged in human populations that was originally called “swine flu†because of its similarity to influenza viruses that can cause infections in pigs, and is now referred to as the 2009 H1N1 influenza virus. This influenza virus spread rapidly from person to person and was declared by the World Health Organization (WHO) to be a new pandemic virus in mid-2009.  It has been the predominant virus in the beginning of the 2009-2010 influenza season.  Some of the current influenza antiviral drugs are able to inhibit many of the “bird flu†viruses and the 2009 H1N1 virus in the laboratory, although it is not known exactly how great their effect may be against illnesses in people. For more information and public health recommendations about the 2009 H1N1 influenza virus go to the website or to the CDC ( and WHO ( websites.  For CDC recommendations regarding use of antivirals in the current influenza season, go to “Updated Interim Recommendations for the Use of Antiviral Medications in the Treatment and Prevention of Influenza for the 2009-2010 Season†(9/22/2009) and related updates.


FDA Approved Drugs for Influenza

This webpage contains several drug information links which provide the trade names, package inserts, and other material related to the four antiviral drugs currently approved by FDA to treat acute, uncomplicated influenza. Zanamivir (approved 1999; Trade Name Relenza; no FDA-approved generics) and oseltamivir phosphate (approved 1999; Trade Name Tamiflu; no FDA-approved generics) are approved for treatment of acute uncomplicated illness due to influenza A and B, and are also approved for preventive use.   Two older drugs, amantadine (Symmetrel, approved 1966; also currently available as generic Amantadine Hydrochloride) and rimantadine (Flumadine, approved 1993; also currently available as generic Rimantadine Hydrochloride), are approved for treatment and prevention of influenza A, but many strains of influenza have now become resistant to these two drugs. Approved ages, doses, and dosing instructions in children are different for each drug, so the individual package inserts should be checked for this information.  In addition, total daily dose and duration of dosing for treatment of acute illness may differ from the dosing and duration for prophylaxis and should be adjusted accordingly.  The anti-influenza antiviral drugs are not a substitute for vaccine and are used only as an adjunct to vaccine in the control of influenza.

The antiviral drug information addresses side effects or adverse events that might be associated with each drug. Because some side effects can be serious and because viruses may become resistant when antiviral drugs are used indiscriminately, decisions on the use of these drugs should be based on individual evaluations of risk and benefit. FDA encourages reporting of serious adverse events (associated with these or any other drugs) to the MedWatch program to facilitate continued updating of safety  information for drug products.

Influenza viruses change over time.  Emergence of resistance mutations could decrease drug effectiveness.  Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs.  Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use these products.

Tamiflu (oseltamivir phosphate) and Relenza (zanamivir) are the two FDA-approved influenza antiviral drugs that are recommended by CDC for use against the 2009 H1N1 influenza virus. The prescribing information for both products is provided below, as well as the Emergency Use Authorizations (EUAs) and fact sheets for certain additional uses of both drugs that have been authorized as part of the response to the 2009 H1N1 public health emergency.

    • Relenza (zanamivir)Includes information on emergency use authorization, patient and healthcare provider fact sheets for use under EUA, and labeling and prescribing information for approved uses
    • Tamiflu (oseltamivir phosphate) Includes information on storage, emergency compounding, pediatric dosing, patient and healthcare provider fact sheets for use under EUA, and labeling and prescribing information for approved uses

The older drugs amantadine and rimantadine are approved for treatment and prevention of influenza A, but many strains of influenza, including 2009 H1N1 influenza, have now become resistant to these two drugs.  CDC currently recommends their use only in situations where specific virus strains are suspected that could be susceptible to these drugs and resistant to other treatment likely to be used.

Use of Investigational Drugs for Influenza: Emergency Use Authorizations, Emergency INDs and Clinical Trials

In addition to the antiviral drugs currently approved for treatment or prevention of influenza, new drugs or new formulations of already approved drugs may be made available through Emergency Use Authorizations, Emergency INDs and clinical trials.  

Emergency Use Authorizations (EUA)

For investigational drugs having sufficient supporting information for risk-benefit determination in a specified emergency situation, in response to certain request procedures FDA may issue Emergency Use Authorizations (EUA) that allow situation-specific use of those drugs outside of the clinical trial development framework and without full FDA approval.  EUAs can also be used to authorize situation-specific uses of approved drugs beyond the limits of their approved labeling.  EUAs issued for certain unapproved uses of Tamiflu and Relenza during the response to the 2009 H1N1 influenza outbreak are described and linked in the sections above.  One unapproved drug, peramivir, has been authorized for intravenous administration to certain hospitalized patients under EUA as part of the 2009 H1N1 influenza response:  information about this EUA is available at the Peramivir Emergency Use Authorization page. 

    • Peramivir IV Includes information on emergency use authorization, patient and healthcare provider fact sheets for use under EUA, and labeling and prescribing information for approved uses
Emergency INDs (EIND)

If a treating physician feels there is an urgent need for an investigational drug in an individual case and there is no suitable clinical trial or EUA available, the physician can contact the manufacturer to inquire about availability under expanded access protocols or individual patient Investigational New Drug emergency use, or Emergency IND.  These mechanisms are described in the recently revised regulations for expanded access, linked below.

Clinical Trials

Clinical trials are conducted to evaluate the safety and efficacy of unapproved products or new uses of approved products.  Some clinical trials may be conducted concurrently with EUA use of some antiviral drugs.  Additional information about clinical trials that are open for enrollment can be found at

The following links provide information about the new expanded access regulations and other aspects of drug development and review, as well as resources to search for additional information on the approval status of drugs and formulations.