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Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

Antiviral Safety Information

The Public Health Emergency determination for 2009 H1N1 Influenza expired on June 23, 2010, terminating Emergency Use Authorizations issued during the pandemic, including some related to antiviral medications.

December 24, 2009 1:30 PM ET

General Antiviral Safety Information

Oseltamivir (Tamiflu®)

  • Emergency Use Authorization (EUA) for Tamiflu®: Fact Sheet for Healthcare Providers
    The Food and Drug Administration (FDA) has issued an EUA for the use of oseltamivir in patients younger than 1 year of age, for use in patients who are symptomatic for more than 2 days, and use in patients with complicated illness requiring hospitalization due to the 2009 H1N1 influenza virus. Please consult this Fact Sheet for general information on possible side effects of oseltamivir.

Zanamivir (Relenza®) 

Peramivir IV

Use of Antiviral Agents in Children and Adolescents

  • Rare Neuropsychiatric Events in Children
    Rarely, transient neuropsychiatric events (delirium, hallucinations, abnormal behavior) have been reported in postmarketing surveillance among persons taking oseltamivir and zanamivir. The majority of reports were among children and adolescents living in Japan. Because influenza infection itself can be associated with a variety of neurologic and behavioral symptoms, including seizures, delirium, and hallucinations, the contribution of the neuraminidase inhibitors to these neuropsychiatric effects is unclear.  Until additional data are available, FDA advises that persons receiving neuraminidase inhibitors be monitored for abnormal behavior.

Use of Antiviral Agents During Pregnancy

While oseltamivir and zanamivir are "Pregnancy Category C" medications, the available risk-benefit data indicate pregnant women with suspected or confirmed influenza should receive prompt antiviral therapy.


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