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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.
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# Updated Interim Recommendations for the Use of Antiviral Medications in the Treatment and Prevention of Influenza for the 2009-2010 Season

terminating Emergency Use Authorizations

December 07, 2009 5:00 PM ET

#### On this Page

                        - Objective
                        - Introduction
                        - Treatment of confirmed or suspected influenza
                        - Antiviral Chemoprophylaxis of exposed individuals
                        - Antiviral drug use for control of influenza outbreaks in institutions
                        - Specific regimens for treatment and chemoprophylaxis of influenza
                        - Antiviral prescription and dispensing considerations
                        - Adverse events and contraindications
                        - Further information

These recommendations contain the following updates:- Information regarding use of  intravenous peramivir under an emergency use authorization
- Information on availability of  renal dosing for peramivir
- Updated  oseltamivir dosing instructions for children younger than 1 year of age based  on weight
- Antiviral treatment and chemoprophylaxis considerations for patients vaccinated with 2009 H1N1 and seasonal influenza vaccines
- Guidance  on early empiric antiviral treatment for patients with progressive or severe  influenza-like illness, regardless of underlying medical conditions
- Guidance  on early empiric antiviral treatment patients with underlying medical  conditions placing them at risk for complications
- Clarification  of treatment considerations for patients with illness longer than 48 hours

These recommendations focus  on the use of antiviral medications for the treatment and chemoprophylaxis of influenza.  As of December 4, 2009, influenza A (H1N1)  virus (2009 H1N1), is the strain responsible for >99% of influenza in the U.S. during  the 2009-2010 influenza season.  For  information about other influenza viruses refer to CDC's Website.  These recommendations were last updated on December  4, 2009, and will be updated periodically as new information becomes available.
Objective
To provide updated recommendations on the use of antiviral agents for treatment and prophylaxis of influenza during the 2009-2010 influenza season.
Introduction
Through November,  2009, ~99% of typed influenza viruses have been 2009 H1N1. The vast majority of  2009 H1N1 viruses tested for drug resistance have been susceptible to oseltamivir  and zanamivir but resistant to the adamantanes (amantadine, rimantadine).  Surveillance data, updated weekly, are  available at Weekly Flu View.  These recommendations will be revised as  needed to adapt to new information on risk factors, antiviral availability and  resistance, or the circulation of other influenza viruses.In general, treatment  with an antiviral agent, when indicated, should begin as soon as possible after  the onset of typical influenza-like symptoms. Influenza illness can present in a range of symptomatology:  from a mild upper respiratory infection to an  acute, life-threatening illness.
- Mild or uncomplicated illness is characterized by typical symptoms like fever (although not everyone with influenza will have a fever), cough, sore throat, rhinorrhea, muscle pain, headache, chills, malaise, sometimes diarrhea and       vomiting, but no shortness of breath and little change in chronic health conditions.
- Progressive illness is characterized by typical symptoms plus signs or symptoms suggesting more than mild illness:  chest pain, poor oxygenation (e.g. tachypnea, hypoxia, labored breathing in children), cardiopulmonary insufficiency (e.g. low blood pressure), CNS impairment (e.g. confusion, altered mental status), severe dehydration, or exacerbations of chronic conditions (e.g. asthma, chronic obstructive pulmonary disease, chronic renal failure, diabetes or other cardiovascular conditions). 
- Severe or complicated illness is characterized by signs of lower respiratory tract disease (e.g., hypoxia requiring supplemental oxygen, abnormal chest radiograph, mechanical ventilation), CNS findings (encephalitis, encephalopathy), complications of low blood pressure (shock, organ failure), myocarditis or rhabdomyolisis, or invasive secondary bacterial infection based on laboratory testing or clinical signs (e.g. persistent high fever and other symptoms beyond three days). 

Influenza viruses are transmitted from person to  person primarily through contact with infected respiratory secretions, especially  airborne droplets generated by coughing and sneezing.  Viral replication and shedding are key considerations  in the timing of treatment, infection control, and chemoprophylaxis.  In general, the incubation  period for influenza is estimated to range from 1 to 4 days with an average of  2 days.  Influenza virus shedding (the time during which a person might be  infectious to another person) begins the day before illness onset and can  persist for 5 to 7 days, although some persons may shed virus for longer  periods, particularly young children and severely  immunocompromised persons.  The amount of virus shed is greatest in the first 2-3 days of illness and  appears to correlate with fever, with higher amounts of virus shed when  temperatures are highest.  For these  recommendations, however, the infectious period for influenza is defined as one  day before fever begins until 24 hours after fever ends.
Treatment of Confirmed or Suspected Influenza**Who to treat**
Prompt empiric treatment is recommended for persons with suspected or confirmed influenza and: 
- Illness requiring hospitalization
- Progressive, severe, or complicated illness, regardless of previous health status, and/or  
- Patients at risk for severe disease (see below for groups at high risk)
**How to treat**- Antiviral drugs: oseltamivir (oral), zanamivir (inhaled)
- For detailed dosing guidelines, see  table 1 below
- Initiate treatment as early as possible after onset of symptoms
- Treat empirically before diagnostic test results are reported
- When definitive diagnosis is indicated, request definitive diagnostic tests (rRT-PCR*,       viral culture) rather than rapid tests (RIDT*, DFA*)

* rRT-PCR: real-time reverse transcriptase polymerase  chain reaction; RIDT:  rapid influenza  diagnostic test, DFA: direct immunofluorescence assay
**Antiviral Drugs for Treatment of Influenza**
The neuraminidase  inhibitors are the drugs of choice for treatment of 2009 H1N1 influenza  and influenza-like illness in both children and adults in the U.S. at this time.

**Oseltamivir** - The neuraminidase inhibitor oseltamivir  formulated as capsules or oral suspension (Tamiflu®) is FDA-approved for the  treatment of uncomplicated acute influenza in patients 1 year and older who  have been symptomatic for no more than 2 days.   The FDA has issued an Emergency Use Authorization (EUA) authorizing treatment  with oseltamivir of patients less than 1 year old with 2009 H1N1 influenza.  In addition, the EUA authorizes treatment of  patients symptomatic with 2009 H1N1 influenza for more than 2 days and patients  sick enough to require hospitalization (see www.cdc.gov/h1n1flu/eua/tamiflu.htm).  

**Zanamivir** - The neuraminidase inhibitor zanamivir  formulated for oral inhalation (Relenza®) is FDA-approved for the treatment of influenza  in patients 7 years of age and older who, similar to approved uses for oseltamivir,  have uncomplicated illness and have been symptomatic for no more than 2  days.  As with oseltamivir, the FDA has  issued an EUA authorizing treatment with zanamivir of patients with 2009 H1N1  influenza who have been symptomatic for more than 2 days and patients sick  enough to require hospitalization (see www.cdc.gov/h1n1flu/eua/relenza.htm ). 

**Peramivir** - A third neuraminidase inhibitor peramivir formulated  for intravenous (IV) administration is an investigational product currently  being evaluated in clinical trials.  As  of October, 2009, safety and/or efficacy data from 1,891 patients with acute  uncomplicated seasonal influenza A has been submitted to the FDA. Efficacy and safety have not been evaluated  in hospitalized patients. Even  though the data are insufficient to allow FDA approval, the FDA issued an EUA  for treatment with peramivir of hospitalized patients with 2009 H1N1 influenza  who have potentially life-threatening suspected or laboratory confirmed  infection. Peramivir IV is available through the CDC upon request of a licensed  physician.  Under the EUA, treatment of adult patients with IV peramivir is approved only  if:  (1) the patient has not responded to  either oral or inhaled antiviral therapy; (2) drug delivery by a route other  than IV is not expected to be dependable or is not feasible; or (3) the  clinician judges IV therapy is appropriate due to other circumstances.  Treatment of pediatric patients is approved  if either of the first two criteria apply.
**Patients who have  severe, complicated, or progressive illness or who are hospitalized**
Treatment is recommended for patients with confirmed or  suspected 2009 H1N1 influenza who have severe, complicated, or progressive  illness or who are hospitalized. The recommended duration of treatment is 5  days. Hospitalized patients with severe infections (such as those with  prolonged infection or who require intensive care unit admission) might require  longer treatment courses.   Even though treatment is most effective when  started in the first 48 hours of illness, limited data from observational studies  of hospitalized patients suggests treatment of persons with prolonged or severe  illness reduces mortality or duration of hospitalization even when treatment is  started more than 48 hours after onset of illness. Antiviral doses recommended  for treatment of 2009 H1N1 influenza in adults or children 1 year of age or  older are the same as those recommended for seasonal influenza (Table 1).  Some experts have advocated use of doubled doses of oseltamivir for some  severely ill patients, although there are no published data demonstrating that  higher doses are more effective.  For  patients unable to take oral medication or in whom oral medication appears to  be ineffective, peramivir for intravenous administration is available from the  CDC under an FDA EUA, although studies of efficacy and safety are limited.  For further information on treatment of  hospitalized patients see, “Antiviral Treatment Options, including Intravenous  Peramivir, for Treatment of Influenza in Hospitalized Patients for the  2009-2010 Season”   and  “Updated  Recommendations for Health Care Providers of Children and Adolescents on the  Use of Antiviral Medications for the Management of 2009 H1N1 and Seasonal  Influenza for the 2009-2010 Season”.
**Patients at Increased  Risk for Complications**
Prompt empiric antiviral  drug treatment is recommended for persons with confirmed or suspected influenza  who are at increased risk for serious morbidity and mortality.  Based on currently available data, approximately 70% of  persons hospitalized with 2009 H1N1 are in one or more of the following groups:
- Children (see below) younger than 2 years old
- Adults 65 years of age or older
- Pregnant women and women up to 2 weeks postpartum (regardless of how the pregnancy ended [live birth, pregnancy termination, preterm birth, miscarriage,       fetal death])
- Persons with certain medical conditions, described below.

**Children:**  Children younger than 2 years of age are at  higher risk for influenza-related complications and have a higher rate of  hospitalization compared to older children. Children aged 2 to 4 years are more  likely to require hospitalization or urgent medical evaluation for influenza  compared with older children and adults, although the risk is much lower than  for children younger than 2 years old. From April through September 2009 hospitalization rates  for laboratory-confirmed 2009 H1N1 influenza were 4.5-fold  higher among children < 2 years of age, 2-fold higher among children 2-4  years of age, and 1.6-fold higher among children 5-17 years of age than among  adults (see Weekly Flu View).   In April, 2009, the FDA  authorized oseltamivir use in children younger than 1 year under an Emergency  Use Authorization (EUA) in response to the current public health emergency  involving 2009 H1N1 influenza. Use of oseltamivir in children younger than 1  year is subject to the terms and conditions of the EUA. Retrospective safety data on  oseltamivir treatment of seasonal influenza in children younger than 1 year old  are limited and suggest that severe adverse events are rare. Prospective data  continue to be collected on safety and efficacy of oseltamivir in this age  group.  Dosing for children younger than  1 year is based on the EUA guidance. Details are provided in Table 1,  below. (See also:  Emergency Use Authorization of Tamiflu (oseltamivir) available at /h1n1flu/eua/). Children  and adolescents under 19 years of age who are receiving long-term aspirin  therapy are also at increased risk. For more detailed information, see “Updated  Recommendations for Health Care Providers of Children and Adolescents on the  Use of Antiviral Medications for the Management of 2009 H1N1 and Seasonal  Influenza for the 2009-2010 Season”. 

**Adults aged 65 years and older:**  Even though persons aged 65 years and older are less  likely to become ill with 2009 H1N1 influenza compared to younger persons, when  they do acquire influenza, they are at higher risk for severe influenza-related  complications. 

**Pregnant women:**  Pregnancy increases the risk of complications,  hospitalization, and severe disease.  One  study estimated the risk of hospitalization for 2009 H1N1 to be four times  higher for pregnant women than for the general population (Jamieson DJ, et al. Lancet. 2009;374:451-458). While oseltamivir  and zanamivir are "Pregnancy Category C" medications, meaning no  clinical studies have been conducted to assess the safety of these medications  for pregnant women, available data suggest pregnant women with suspected or  confirmed influenza should receive prompt antiviral therapy, and pregnancy  should not be considered a contraindication to treatment with oseltamivir or  zanamivir. Oseltamivir is preferred for treatment of pregnant women because of  its systemic activity. Anecdotal reports  suggest postpartum women, similar to pregnant women, might be at increased risk  for severe complications and death from 2009 H1N1 influenza.  The transition to normal immune, cardiac, and  respiratory function occurs quickly, but not immediately after delivery.  Therefore, the increased risk associated with  pregnancy should be considered to extend for 2 weeks postpartum regardless of  the outcome of the pregnancy (including live birth, premature birth, termination of  pregnancy, miscarriage, fetal death).  Prompt empiric antiviral treatment is  indicated for suspected or confirmed 2009 H1N1 influenza in women who are up to  2 weeks postpartum regardless of how the pregnancy ended.

**Medical conditions****:**  The following medical conditions have been  associated with increased risk of complications from influenza:
Asthma
Neurological and neuro-developmental conditions [including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy (seizure disorders), stroke, intellectual disability (mental retardation), moderate to severe developmental delay, muscular dystrophy, or spinal cord        injury].   
Chronic  lung disease   (such as chronic obstructive pulmonary disease         [COPD] and cystic fibrosis) 
Heart disease
 (such as congenital heart disease, congestive heart failure and coronary artery disease)   
Blood disorders (such as sickle cell disease) 
Endocrine disorders (such as 
diabetes
 mellitus) 
Kidney disorders 
Liver disorders 
Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders) 
Weakened immune system
 due to disease or medication (such as people with 
HIV or AIDS
, or cancer, or those on chronic steroids)
People younger than 19 years of age who are receiving long-term aspirin therapy

Local public health authorities might provide additional  guidance about prioritizing treatment within groups at higher risk for severe  infection.
**Clinical  Assessment**
While most persons who have had confirmed or  suspected 2009 H1N1 influenza have had a mild, uncomplicated self-limited  respiratory illness similar to typical seasonal influenza and while persons not  considered to be at increased risk of developing severe or complicated illness  may not require treatment, they can be considered for antiviral treatment.  Benefits of treating such patients might  include a reduced duration of illness.   However, based on experience with seasonal influenza treatment, patients  not considered to be at increased risk of developing severe or complicated  illness and who have mild, uncomplicated illness are not likely to benefit from  treatment if initiated more than 48 hours after illness onset.  Clinical judgment is always an essential part  of treatment decisions.

People who are already recovering from influenza do not need antiviral  medications for treatment.  Options for close follow-up should be carefully  considered. Clinicians who prefer not to treat empirically should discuss signs  and symptoms of worsening illness with such patients and arrange for follow up  at least by telephone.

**Clinical  algorithm for consideration in the assessment of persons with mild or  uncomplicated influenza illness**
**Initiation of  Treatment**
Treatment should be started empirically based on clinical  judgment as early as possible even before definitive diagnostic test results  become available, i.e., **treatment should  not wait for laboratory confirmation of influenza.**Treatment is most effective when started  in the first 48 hours of illness. As noted above, however, evidence suggests treatment  may benefit patients with prolonged or severe illness even when started more  than 48 hours after the onset of illness.
- Definitive testing for 2009 H1N1 requires real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) or viral culture. These tests should be prioritized for persons with suspected or       confirmed influenza requiring hospitalization and based on guidelines from local and state health departments.
- Rapid Influenza Diagnostic Tests (RIDTs) should not be used to rule out influenza because false negative results are common. The sensitivity of rapid tests in detecting 2009 H1N1 has ranged from 10% to 70%. Clinicians should not withhold treatment based on a  negative rapid test result .  Information on the use of  rapid influenza diagnostic tests  (RIDTs) is available online. 

Methods for  reducing delays in treatment initiation include:
- Inform persons at increased risk for influenza complications about the signs and symptoms of influenza and the need for early treatment after onset of symptoms.
- Ensure rapid access to telephone consultation and clinical evaluation for these patients as well as patients who report severe illness.
- Consider empiric treatment of patients at increased risk for influenza complications based on telephone contact if hospitalization is not indicated and if this will substantially reduce delay before treatment is initiated. 
- Request that patients at increased risk for influenza complications contact their       provider if signs or symptoms of influenza develop, obtain medication as quickly as possible if prescribed by the provider, and initiate treatment. Providers should take into account patient reliability, ability to understand the information about symptoms of influenza, and access to a pharmacy when considering ways to reduce treatment delays. 
- Counsel patients about influenza antiviral benefits and adverse effects, the potential for       continued susceptibility to influenza virus infection after treatment is completed (because of other circulating influenza viruses or if illness was due to another cause), and the need to again seek early access to healthcare consultation if symptoms recur. 
- For persons exposed to influenza, close monitoring for symptoms and early treatment is emphasized as an  alternative to chemoprophylaxis.  Household  or close contacts (with risk factors for influenza complications) of confirmed  or suspected cases can be counseled about the early signs and symptoms of  influenza, and advised to immediately contact their healthcare provider for  evaluation and possible early treatment if clinical signs or symptoms develop.
**Infection  Control Measures for Patients Treated for Influenza**
Following are recommendations  to minimize exposure to infected patients.   For more detailed recommendations  “Antiviral  Chemoprophylaxis of Exposed Individuals.”
**Reducing Transmission  from Infected Patients**
The infectious interval for influenza is defined in the Introduction.  Because some studies have shown that  treatment reduces the duration and magnitude of viral shedding, treatment might  also reduce infectiousness.  However,  symptomatic individuals who are receiving treatment should be advised that they remain  potentially infectious to others while on treatment. Despite treatment with  antiviral agents, patients may continue to shed influenza virus for up to four  or more days after beginning therapy. Therefore, patients should maintain good cough  etiquette, respiratory hygiene, and handwashing practices during the entire  period on therapy to prevent the transmission of virus to close contacts.

Close contact, for the purposes of this document, is defined as having cared  for or lived with a person who is a confirmed, probable, or suspected case of  influenza, or having been in a setting where there was a high likelihood of  contact with respiratory droplets and/or body fluids of such a person. Examples  of close contact include sharing eating or drinking utensils, or any other  contact between persons likely to result in exposure to respiratory droplets.  Close contact typically does not include activities such as walking by an infected  person or sitting across from a symptomatic patient in a waiting room or  office.                            Health care  workers should instruct their patients in these behavioral measures.  More detailed infection control measures for  individuals, for preventing occupational infection, and for institutional  settings are described below.
**Protection of health care workers**
Key recommendations  to protect health care workers from being infected with influenza virus include: 
- Appropriate administrative controls (e.g. healthcare personnel staying home  from work when ill and triaging for identification of potentially infectious  patients), respiratory and hand hygiene, personal protective equipment, and  vaccination should be instituted to reduce the risk of exposure or infection  for healthcare personnel and first responders.    
- For more information, see  "Questions and Answers about CDC’s Interim Guidance on Infection Control Measures for 2009 H1N1 Influenza in Healthcare Settings, Including Protection of Healthcare Personnel"
**Additional  Considerations for Treatment****Children and Over-the-Counter Cold Medications, Including  Aspirin**
Aspirin or aspirin-containing products (e.g. bismuth subsalicylate –  PeptoBismol) should not be administered to any child or adolescent less than 19  years of age with confirmed or suspected influenza due to the risk of Reye’s  syndrome. For relief of fever, other anti-pyretic medications such as  acetaminophen or non-steroidal anti-inflammatory drugs are recommended.  Children younger than 4 years of age should  not be given over-the-counter cold medications without first speaking with a  healthcare provide.
**Previous Vaccination for 2009 H1N1 or Seasonal Influenza**
Seasonal influenza  viruses may also circulate and cause illness this 2009-2010 influenza season,  possibly at the same time as the 2009 H1N1 outbreaks are occurring. The  severity, amount and timing of illness that 2009 H1N1 and seasonal influenza viruses  will cause are uncertain. In October  2009, inactivated and live attenuated 2009 H1N1 monovalent influenza vaccines  became available in the United States. All persons in a recommended  vaccination target group should be vaccinated with the 2009 H1N1 monovalent vaccine  and the seasonal  influenza vaccine.

The seasonal influenza vaccine is not expected  to provide protection against the 2009 H1N1 influenza or vice-versa.  Moreover, these  vaccines are not  100% effective against infection.  In  addition, vaccines are not effective immediately after administration.  At least 2 weeks must pass for the vaccine to  take effect. Therefore, a history of vaccination does not rule out influenza.  Previous vaccination is not a contraindication to antiviral drug treatment.

Treatment recommendations for vaccinated individuals should parallel  those for unvaccinated persons. 

Persons who are vaccinated with live attenuated influenza vaccines and  who are given antiviral drugs within 48 hours before or up to two weeks after  vaccination might not develop immunity and should be revaccinated.
**Bacterial Co-infection**
Clinicians are reminded to  consider bacterial co-infections that can occur during or after influenza.  Therefore, empiric treatment of community  acquired pneumonia should include oseltamivir and antibacterial drugs when influenza  is circulating in the community and the clinician believes that influenza may  be causing or coinciding with the community-acquired pneumonia. (See Infectious  Disease Society of America/American Thoracic Society Consensus Guidelines on the  Management of Community-Acquired Pneumonia in Adults. Clinical Infectious Diseases 2007;44:S27–72).
**Treatment of influenza when oseltamivir-resistant  viruses are circulating**
Oseltamivir resistance is  common among seasonal influenza A (H1N1) viruses. These viruses typically  remain susceptible to zanamivir, rimantadine, and amantadine. However, since  April 2009, very few seasonal H1N1 viruses have circulated in the United States.  Therefore, treatment, when indicated, with either oseltamivir or zanamivir is  appropriate. However, if viral surveillance data indicate that  oseltamivir-resistant seasonal H1N1 viruses have become more common or are  associated with identified community outbreaks, zanamivir or a combination of  oseltamivir and rimantadine or amantadine should be considered for use as  empiric treatment for patients who might have oseltamivir-resistant seasonal  human influenza A (H1N1) virus infection. National surveillance data on  influenza viruses circulating in the United States is available at the Weekly Flu View. State and local health departments are also a source of viral  surveillance data in some areas. Guidance on empiric treatment recommendations  when multiple influenza strains are circulating is available at "CDC Issues Interim Recommendations for the Use of Influenza Antiviral Medications in the Setting of Oseltamivir Resistance among Circulating Influenza A (H1N1) Viruses,                       2008-09 Influenza Season".
Antiviral Chemoprophylaxis of exposed individuals**Definitions used, whom to treat prophylactically****Infectious    period**- One day before fever begins until 24 hours after fever ends.
**Close contact, defined by possible modes of transmission**- Droplet exposure of mucosal surfaces (e.g. nose, moth, and eyes) by    respiratory secretions from coughing or sneezing 
- Contact, usually of hands, with an infectious patient or fomite (a    surface that is contaminated with secretions) followed by self-inoculation of    virus onto mucosal surfaces such as those of the nose, mouth, and eyes; and 
- Small particle aerosols in the vicinity of the infectious individual. 
**Who may be considered for antiviral chemoprophylaxis**- The following persons who are a close contact of a person with suspected    or confirmed 2009 H1N1 influenza during the infectious period:
Persons at high risk for complications of influenza;
Health care workers and emergency medical personnel;
Pregnant    women.

**Whom not to treat chemoprophylactically**- Groups of healthy children or adults based on potential exposures in the community, workplace, school, camp or other settings; 
- If  >48 hours have elapsed since the last close contact
- The close contact did not occur during the infectious period
**How to prophylax**- Antiviral drugs: oseltamivir (oral), zanamivir (inhaled)
- For detailed dosing guidelines, see tables 1 and 2 below
**Consider early treatment as an alternative to chemoprophylaxis****Antiviral Drugs for Chemoprophylaxis**
The  neuraminidase inhibitors, oseltamivir and zanamivir, are the drugs of choice for chemoprophylaxis of 2009  H1N1 influenza-exposed  children and adults in the U.S.  at this time. Oseltamivir formulated as capsules or oral suspension (Tamiflu®)  is FDA-approved for prophylaxis of influenza in patients 1 year and older.  The FDA has issued an Emergency Use  Authorization for oseltamivir prophylaxis of patients less than 1 year old (see  www.cdc.gov/h1n1flu/eua/tamiflu.htm).   Zanamivir formulated for oral inhalation (Relenza®) is FDA-approved for  prophylaxis of influenza in patients 5 years of age and older. The duration of  chemoprophylaxis is 10 days. Recommendations for prophylaxis of currently  circulating 2009 H1N1 influenza with these drugs are described below as well as  in Fact Sheets developed under the Emergency Use Authorizations (see Rrelenza and Tamiflu ).
**Early Treatment  as an Alternative to Chemoprophylaxis**
Early recognition of illness and  prompt initiation of treatment is emphasized as an alternative to  chemoprophylaxis after a suspected exposure. 
- Persons with risk factors for influenza complications who are household or  close contacts of confirmed or suspected cases, and healthcare personnel who  have occupational exposures, should be counseled about the early signs and  symptoms of influenza, and advised to immediately contact their healthcare  provider for evaluation and early treatment when indicated if clinical signs or  symptoms develop. 
- Healthcare providers should use clinical judgment regarding situations  where early recognition of illness and treatment might be an appropriate  alternative to chemoprophylaxis. 
- Early recognition of illness and treatment when  indicated is preferred to chemoprophylaxis for healthy vaccinated persons,  including healthcare workers, after a suspected exposure.   

Patients given post-exposure chemoprophylaxis should  be informed that the chemoprophylaxis lowers but does not eliminate the risk of  influenza and that protection stops when the medication course is stopped.  Patients receiving chemoprophylaxis should be encouraged to seek medical  evaluation as soon as they develop a febrile respiratory illness that might  indicate influenza. 
Antiviral Drug Use for Control of Outbreaks in Institutions
Use of antiviral drugs for treatment and chemoprophylaxis  of influenza has been a cornerstone of the control of seasonal influenza  outbreaks in nursing homes and other long-term care facilities that house large  numbers of patients at higher risk for influenza complications. (See MMWR: Prevention and Control  of Influenza: Recommendations of the Advisory Committee on Immunization  Practices (ACIP), 2008). As of October 29, 2009, no outbreaks of 2009 H1N1  have been reported in nursing homes, but at least one cluster has been reported  in a long-term care facility.  When 2009  H1N1 outbreaks occur within such facilities, it is recommended that ill  patients be treated with oseltamivir or zanamivir and that chemoprophylaxis  with either oseltamivir or zanamivir be started as early as possible to reduce  the spread of the virus as is recommended for seasonal influenza outbreaks in  such settings. Additional guidance for infection control measures in long-term  care facilities can be found at: Using  Antiviral Medications to Control Influenza Outbreaks in Institutions.

In addition to use in nursing homes, antiviral  chemoprophylaxis also can be considered for controlling influenza outbreaks in  other closed or semi-closed settings (e.g., correctional facilities, or other  settings in which persons live in close proximity) where large numbers of  persons at higher risk for influenza complications are housed. For more  information about influenza outbreaks in facilities see: 
- Prevention  and Control of Influenza: Recommendations of the Advisory Committee on  Immunization Practices (ACIP), 2008
-  Seasonal Influenza in  Adults and Children—Diagnosis, Treatment, Chemoprophylaxis, and Institutional  Outbreak Management: Clinical Practice Guidelines of the Infectious Diseases  Society of America
- Interim Guidance for Correctional and Detention Facilities on Novel  Influenza A (H1N1) Virus
- Interim Guidance for Emergency Shelters on the Novel Influenza A (H1N1)  Virus

Outbreaks of influenza in schools, camps, workplaces  and other group settings should not be managed by providing chemoprophylaxis to  all persons potentially exposed to influenza viruses. The healthy populations  typically present in these settings should be educated about the signs and  symptoms of influenza, and urged to consult their healthcare provider if severe  illness develops. Post-exposure chemoprophylaxis can be considered for those  who meet the above criteria for exposure and who have a medical condition or  are of an age that confers a higher risk for influenza complications. An  emphasis on early evaluation and treatment, as described above, is an  alternative. Persons in these settings also should be educated about hygiene  and infection control measures that can reduce transmission of influenza  viruses. 
Specific Regimens for Treatment and Chemoprophylaxis of 2009 H1N1 Influenza A**Treatment and Chemoprophylaxis Regimens for Adults and  Children by Age and Weight****Table 1. Antiviral medication dosing recommendations for treatment or chemoprophylaxis of 2009 H1N1 infection.(Extracted from product information for Tamiflu® and Relenza®)****Medication**Treatment      (5 days)Chemoprophylaxis      (10 days)**Oseltamivir1****Adults** 75 mg twice daily75 mg once daily**Children ≥ 12 months**Body Weight (kg)Body Weight (lbs)  ≤15 kg≤33lbs30 mg twice daily30 mg once daily> 15 kg to 23 kg>33 lbs to 51 lbs45 mg twice daily45 mg once daily>23 kg to 40 kg>51 lbs to 88 lbs60 mg twice daily60 mg once daily>40 kg>88 lbs75 mg twice daily75 mg once daily**Children 3 months to < 12 months2**  3 mg/kg/dose twice daily3 mg/kg/dose once per day**Children 0 to < 3 months3**  3 mg/kg/dose twice dailyNot recommended unless  situation judged critical due to limited data on use in this age group**Zanamivir4****Adults** 10 mg (two 5-mg inhalations) twice  daily10 mg (two 5-mg inhalations) once  daily**Children (≥7 years or older for treatment, ≥5 years for chemoprophylaxis)** 10 mg (two 5-mg inhalations)  twice daily  10 mg (two 5-mg inhalations)  once daily- Oseltamivir is administered orally without regard to meals, although          administration with meals may improve gastrointestinal tolerability.          Oseltamivir is available as Tamiflu(r) in 30 mg, 45 mg, and 75 mg          capsules; and a as a powder for oral suspension that is reconstituted to          provide a final concentration of 12 mg/mL.  If the commercially          manufactured oral suspension is not available, the capsules may be          opened and the contents mixed with a sweetened liquid to mask the bitter          taste or a suspension can be compounded by retail pharmacies (final          concentration 15 mg/mL).  In patients with renal insufficiency the dose          should be adjusted based on creatinine clearance.  For treatment of          patients with creatinine clearance 10-30 mL/min:  75 mg once daily for 5          days.  For chemoprophylaxis of patients with creatinine clearance 10-30          mL/min:  30 mg once daily or 75 mg once every other day continuing for        10 days after the exposure.      
- Weight-based  dosing is preferred, however, if weight is not known, dosing by age for treatment  (give two doses per day) or prophylaxis (give one dose per day) of influenza in  full-term infants younger than 1 year of age may be necessary:  0-3 months (treatment only) = 12 mg (1 mL of  12 mg/mL commercial suspension); 3-5 months = 20 mg once daily (1.6 mL of 12  mg/mL of commercial suspension), 6-11 months = 25 mg (2 mL of 12 mg/mL  commercial suspension) once daily).      
- Current weight-based dosing  recommendations are  not  intended for premature  infants.  Premature infants may have slower clearance of Tamiflu due to  immature renal function, and doses recommended for full term infants may lead  to very high drug concentrations in this age group.  Very limited data  from a cohort of premature infants receiving an average dose of 1.7 mg/kg twice  daily demonstrated drug concentrations higher than those observed with the  recommended treatment dose in term infants (3 mg/kg twice daily).   Observed drug concentrations were highly variable among premature  infants.  These data are insufficient to recommend a specific dose of  Tamiflu for premature infants.      
- Zanamivir is administered by inhalation using a  proprietary “Diskhaler” device distributed together with the medication.  Zanamivir is a dry powder, not an aerosol,  and should not be administered using nebulizers, ventilators, or other devices  typically used for administering medications in aerosolized solutions. Zanamivir is not recommended for persons with chronic respiratory  diseases such as asthma or chronic obstructive pulmonary disease that increase  the risk of bronchospasm.      
Antiviral Prescription and Dispensing  Considerations**Alternatives to Tamiflu® Oral Suspension for  Pediatric Patients**
Even though  commercially-manufactured Tamiflu® Oral Suspension (12 mg/mL) is the preferred  product for patients who have difficulty swallowing capsules or where lower  doses are needed, this product may not be locally available.

For patients who are  less than one year old, there is one alternative: 
- a suspension compounded by a retail pharmacy ( FDA Drug Safety Information: Emergency Compounding of an Oral Suspension from Tamiflu 75 mg Capsules (Final Concentration 15 mg/mL ) 

For children who are at least one year old there  are two alternatives:
- a suspension compounded by a retail pharmacy (same link as above) 
- 30mg, 45mg, or 75 mg capsules, which may be mixed into a sweetened liquid by a caregiver if the       child cannot swallow capsules (" Opening and Mixing Tamiflu Capsules with Liquids if Child Cannot Swallow Capsules "                          **Compounding Oseltamivir Suspension – Potential  Dosing Errors**  The commercially-manufactured Tamiflu® Oral Suspension concentration is 12  mg/mL; the compounded suspension concentration is 15 mg/mL.  **When prescribing Tamiflu® Oral Suspension, prescribers should specify the      concentration if prescribing in mL or teaspoons, or they should prescribe the dose in milligrams (mg).**  **Additional information can be found  at:**    - H1N1 Flu: Resources for  Pharmacists
  - Institute for Safe Medication Practices Safety Alert: Tamiflu®  Oral Suspension Shortage Contributing to Dosing Errors  **Commercial Tamiflu® Oral Suspension – Potential Dosing Device Errors**  Pharmacists with access to  Tamiflu® Oral Suspension should be aware that an oral dosing dispenser with 30  mg, 45 mg, and 60 mg graduations is provided in the manufacturer’s packaging,  rather than graduations in milliliters (mL) or teaspoons (tsp). There have been  cases where the units of measure on the prescription dosing instructions (mL,  tsp) do not match the units on the dosing device (mg), which can lead to  confusion and dosing errors. When dispensing commercially-manufactured Tamiflu®  Oral Suspension, pharmacists should ensure the units of measure on the dosing  instructions match the dosing device provided. If dosing instructions specify  administration using mL or tsp the device included in the Tamiflu® product  package should be removed and replaced with an appropriate measuring device.  **When dispensing commercially-manufactured Tamiflu® Oral Suspension, please ensure that the      units of measure on the dosing instructions match the dosing device provided.****For children younger than 1 year of age, the oral dosing dispenser that is included in the product package should always be removed and replaced with an appropriate measuring device as it is not designed for measuring doses < 30 mg.**  **Additional information can be found at:**    - H1N1 Flu: Resources for  Pharmacists
  - FDA Public Health Alert: Potential Medication Errors with Tamiflu for Oral  Suspension    Adverse  Events and  Contraindications  Oseltamivir and zanamivir are generally well-tolerated among  FDA-approved age groups. Nausea and vomiting were reported more frequently  among adults receiving oseltamivir for treatment (nausea without vomiting,  approximately 10%; vomiting, approximately 9%) than among persons receiving  placebo (nausea without vomiting, approximately 6%; vomiting, approximately  3%). Among children treated with oseltamivir, 14% had vomiting, compared with  8.5% of placebo recipients. Oseltamivir suspension is formulated with sorbitol,  which may be associated with diarrhea and abdominal pain in patients who are  fructose-intolerant. Retrospective  safety data on oseltamivir treatment of seasonal influenza in children younger  than 1 year old is limited and suggest that severe adverse events are rare.  Prospective data continue to be collected on safety and efficacy of oseltamivir  in this age group.  Allergic reactions  (rash, swelling of the face or tongue, anaphylaxis) have been reported in  clinical practice from both oseltamivir and zanamivir.   Zanamivir, an inhaled medication, can induce bronchospasm  and is not recommended for treatment for patients with an underlying increased  risk of bronchospasm. Zanamivir should only be used as directed in the  prescribing information by using the Diskhaler device provided with the drug  product.  The commercial zanamivir  formulation (Relenza®  Inhalation Powder) is a mixture of zanamivir active drug substance and lactose  drug carrier. This formulation is not designed or intended to be used in any  nebulizer or mechanical ventilator as there is a risk that the lactose  sugar can obstruct proper functioning of mechanical ventilator equipment.  Although there are published and  unpublished reports of zanamivir being used via nebulizer and mask in clinical  trials, the currently available commercial formulation is not designed or  intended to be administered by nebulization.    Rarely, transient neuropsychiatric events (self-injury or  delirium) 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, whether  the neuraminidase inhibitors are directly responsible for these  neuropsychiatric effects is unclear. To date, retrospective analyses conducted  by Roche, the manufacturer of oseltamivir, have not found evidence for an  increased risk of neuropsychiatric events after oseltamivir use. Until  additional data are available, FDA advises that persons receiving neuraminidase  inhibitors be monitored for abnormal behavior. For additional information  please refer to the FDA MedWatch Safety Alert: Tamiflu®.  Data on the safety of peramivir IV  are limited and are summarized in the EUA Factsheet for Health Care  Professionals. After a single dose of 200 mg or 400 mg  peramivir IV, adverse clinical events and laboratory abnormalities were no more  frequent than placebo.  Among  hospitalized patients treated with 5 days of peramivir IV, 200 mg or 400 mg, overall  adverse events were recorded in 54% of patients compared with 41% of patients  treated with oseltamivir 75 mg orally twice daily.  Serious adverse events were noted in 4% of  patients receiving 200 mg daily, 17% of patients receiving 400 mg, and 9% of  patients receiving oseltamivir.  Diarrhea  and psychiatric events were more common among peramivir recipients than  oseltamivir recipients.  In terms of  laboratory parameters, clinicians should monitor blood counts, electrolytes,  renal function, urinalysis, and hepatic profile as recommended in the EUA. Given the limited safety data on peramivir, mandatory reporting  requirements are part of the conditions of the EUA.  Health care providers (or designee) must  report adverse events and all medication errors associated with peramivir to  FDA’s MedWatch program within 7 calendar days from the onset of the adverse  event, including follow-up as requested.  **Reporting Adverse  Events**  Health care professionals should report all serious adverse  events (SAE) after antiviral medication use promptly to MedWatch, the FDA’s  adverse event reporting program for medications.    For More Information  **For further information about influenza and antiviral  medications, including contraindications and adverse effects, please see the  following:**    - Questions&Answers: Antiviral Drugs, 2009-2010 Flu Season
  - Antiviral  Agents for Seasonal Influenza: Side Effects and Adverse Reactions . 
  - Harper SA, Bradley JS, Englund  JA, et al.  Infectious Diseases  Society of America Guidelines. Seasonal Influenza in Adults and  Children—Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak  Management: Clinical Practice Guidelines of the Infectious Diseases Society of  America.
  - Jain,  S et al.  Hospitalized  Patients with 2009 H1N1 Influenza in the United States, April-June 2009 . N  Engl J Med 2009;361. 
  - Jamieson DJ, et al. H1N1 2009 influenza virus infection during pregnancy in  the USA.  Lancet  2009;374:451-8. 
  - CDC.  Intensive-Care  Patients With Severe Novel Influenza A (H1N1) Virus Infection --- Michigan,  June 2009.  MMWR Morb Mortal Wkly Rep 2009:58:749-52. 
  - Rasmussen SA. Pandemic  Influenza and Pregnant Women: Summary of a Meeting of Experts. Am J Public  Health 2009; 99 (S2): S248-S254.  Links to non-federal organizations are provided solely  as a service to our users. These links do not constitute an endorsement of  these organizations or their programs by CDC or the federal government, and  none should be inferred. CDC is not responsible for the content of the  individual organization Web pages found at these links.                     - Print page
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