Use of Antiviral Agents

Last updated December 16, 2010. At the current time, this content is considered historical and will not be updated until further notice.

Note: This document is best viewed with Internet Explorer for both format and function.

CDC Treatment Recommendations for the 2010-11 Influenza Season
Antiviral Treatment for Pregnant Women
Antiviral Treatment for Immunocompromised Patients
Antiviral Resistance

CDC Treatment Recommendations for the 2010-11 Influenza Season

According to 2010-11 recommendations from the CDC (CDC 2010: Interim guidance on the use of influenza antiviral agents during the 2010-2011 influenza season), antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who:

• Has severe, complicated, or progressive illness

• Is hospitalized
• Is at higher risk for influenza complications as follows:
• Children younger than 2 years old (Note: neuraminidase inhibitors are not licensed for treatment of children <1 year of age [oseltamivir] or <7 years of age [zanamivir]. Oseltamivir was used for treatment of pH1N1 2009 influenza virus infection in children <1 year of age under an Emergency Use Authorization [EUA], but this EUA has expired. However, the CDC recommends that clinicians who treat children aged 3 to11 months administer 3 mg/kg body weight/dose twice per day for treatment, and 3 mg/kg body weight/dose once per day for chemoprophylaxis. Infants aged <3 months are recommended to receive 3 mg/kg body weight /dose twice per day for treatment. However, chemoprophylaxis for infants aged <3 months is not recommended unless the exposure situation is judged to be critical, because of a lack of data on use of oseltamivir in this age-group.)
• Adults 65 years of age and older
• Persons with the following conditions: chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), neurological, neuromuscular, or metabolic disorders (including diabetes mellitus)
• Persons with immunosuppression, including that caused by medications or by HIV infection
• Women who are pregnant or postpartum (within 2 weeks after delivery)
• Persons younger than 19 years of age who are receiving long-term aspirin therapy
• American Indians and Alaskan Natives
• Persons who are morbidly obese (body mass index ≥40)
• Residents of nursing homes and other chronic-care facilities

Clinical judgment, based on the patient's disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, should be considered when making antiviral treatment decisions for high-risk outpatients. When indicated, antiviral treatment should be started as soon as possible after illness onset.

• The greatest benefit is when antiviral treatment is started within 48 hours of influenza illness onset.
• Antiviral treatment may still be beneficial in patients with severe, complicated, or progressive illness, and in hospitalized patients when administered >48 hours from illness onset.

Antiviral treatment also can be considered for any previously healthy, non–high-risk, symptomatic outpatient with confirmed or suspected influenza based on clinical judgment, if treatment can be initiated within 48 hours of illness onset.

In areas with limited antiviral medication availability, local public health authorities might provide additional guidance about prioritizing treatment within groups at higher risk for complications.

Dosing recommendations are outlined in the table below.

Oseltamivir and Zanamivir Prescribing Information
Agent, group		Treatment	Chemoprophylaxis
Oseltamivir
Adults		75-mg capsule twice per day for 5 days	75-mg capsule once per day
Children (age >12 mo), weight	<15 kg	30 mg twice daily	30 mg once per day
	15-23 kg	45 mg twice daily	45 mg once per day
	>23-40 kg	60 mg twice daily	60 mg once per day
	>40 kg	75 mg twice daily	75 mg once per day
Zanamivir
Adults		Two 5-mg inhalations (10 mg total) twice per day	Two 5-mg inhalations (10 mg total) once per day
Children		Two 5-mg inhalations (10 mg total) twice per day (age, 7 years or older)	Two 5-mg inhalations (10 mg total) once per day (age, 5 years or older)

An increased dose of the drug (150 mg twice daily in adults) and an increased duration of therapy (a total of 10 days) with no treatment interruptions has been used in patients with pneumonia or evidence of clinical progression (Writing Committee of the WHO Consultation on Clinical Aspects of Pandemic H1N1 2009 Influenza).

Back to top

Antiviral Treatment for Pregnant Women

• Pregnancy should not be considered a contraindication to oseltamivir or zanamivir use. Pregnant women are known to be at higher risk for complications from infection with seasonal influenza viruses. Furthermore, pregnant women are at higher risk for influenza complications from pH1N1 2009.
• Oseltamivir, zanamivir, rimantadine, and amantadine are "Pregnancy Category C" medications, indicating that data from clinical studies are not adequate to fully assess the safety of these medications for pregnant women. Although a few adverse effects have been occasionally reported in pregnant women who took these medications, no causal relation between the use of these medications and those adverse events has been established. One retrospective cohort study found no evidence of an association between oseltamivir use during pregnancy and a variety of adverse events, including preterm birth, premature rupture of membranes, increased duration of hospital stay for mother or neonate, malformations, or fetal weight (Greer 2010).

• The California Department of Public Health reviewed data from 94 pregnant, 8 postpartum, and 137 non-pregnant women of reproductive age who were hospitalized with pH1N1 2009 influenza. In total, 18 pregnant women and 4 postpartum women (22/102 [22%]) required intensive care, and 8 (8%) died. Late antiviral treatment (³2 days after symptom onset) was associated with admission to the intensive care unit (ICU) or death (Louie 2010).

Back to top

Antiviral Treatment for Immunocompromised Patients

• A multicenter cohort study of adults and children who had received solid-organ transplants and had confirmed influenza A infection showed that antiviral treatment initiated within 48 hours of symptom onset was associated with a decrease in admission to the hospital and ICU, a need for mechanical ventilation, and death (Kumar 2010).
• In a study of 45 immunocompromised patients with either cancer or hematopoietic stem-cell transplantation who developed pH1N1 2009 infection, all received antiviral therapy, and no patients died (Redelman-Sidi 2010).

Back to top

Antiviral Resistance

To date, most isolates of the pH1N1 2009 virus generally have been susceptible to the neuraminidase inhibitors oseltamivir and zanamivir, although sporadic instances or small clusters of resistant isolates have been reported.

As of August 2010, more than 300 cases of oseltamivir-resistant pH1N1 2009 influenza had been reported to the WHO (WHO 2010: Weekly update on oseltamivir resistance to influenza A (H1N1) 2009 viruses). All of these oseltamivir-resistant isolates except one had the same mutation in the neuraminidase gene (H275Y), conferring resistance to oseltamivir but not to zanamivir.

Resistant isolates predominantly have been obtained from treated patients and immunosuppressed patients receiving prolonged therapy (Harvala 2010, Tramontana 2010), although in some instances, resistant isolates have been found in patients who had no exposure to oseltamivir.

Back to top