The Centers for Disease Control and Prevention updated its recommendations on early and late antiviral treatment during the 2009–2010 influenza season, and provided more guidance on the use of the investigational antiviral drug peramivir.
When to Start Antivirals
▸ Patients with mild, uncomplicated illness who are not considered to be at increased risk of developing severe or complicated illness are not likely to benefit from antiviral treatment if started more than 48 hours after illness onset. Similarly, patients who are already recovering from influenza do not need antiviral medications. For patients who present within 48 hours of onset, clinical judgment should be used to decide if patients with mild or uncomplicated illness and no risk factors need antiviral drugs.
▸ Antiviral regimens lasting 5 days are recommended for patients with confirmed or suspected 2009 H1N1 influenza who have severe, complicated, or progressive illness, or who are hospitalized. The 5-day treatment duration might be extended in some patients. Limited data from observational studies of hospitalized patients suggest that the initiation of antiviral treatment more than 48 hours after onset reduces mortality or duration of hospitalization in patients with prolonged or severe illness.
▸ Promptly begin empiric antiviral therapy for patients with confirmed or suspected influenza who have an increased risk for complications, the CDC advised. These include children and adolescents younger than 19 years of age who are receiving long-term aspirin therapy, adults aged 65 years and older, pregnant women, and individuals with certain medical conditions (asthma; neurological and neurodevelopmental disorders; chronic lung disease; heart disease; blood, endocrine, kidney, liver, or metabolic disorders; and a weakened immune system due to disease or medication).
▸ Available data suggest pregnant women should receive prompt antiviral therapy, although no clinical studies have assessed the safety and efficacy of oseltamivir (Tamiflu) or zanamivir (Relenza) for pregnant women. The systemic activity of oseltamivir makes it the preferred treatment for pregnant women. The agency also advises prompt antiviral treatment of women up to 2 weeks post partum with suspected or confirmed 2009 H1N1 influenza (regardless of the pregnancy outcome), because anecdotal reports have suggested that they also may be at risk for severe complications and death.
Giving Antivirals to Vaccinated Patients
A history of vaccination does not rule out influenza, the CDC advised, because vaccination for 2009 H1N1 or seasonal influenza is effective only after 2 weeks. In addition, each vaccine is not expected to provide protection against influenza viruses other than the targeted virus. The agency recommends treating vaccinated patients as if they had not been vaccinated. People who are vaccinated with live attenuated influenza vaccines and who are given antivirals within 48 hours before or up to 2 weeks after vaccination might not develop immunity and should be revaccinated.
Peramivir Availability and Dosing
The Food and Drug Administration (FDA) approved the use of intravenously administered peramivir under an Emergency Use Authorization for hospitalized patients who have not responded to either oral oseltamivir or inhaled zanamivir. Peramivir also is indicated when patients are expected not to have a dependable or feasible route of delivery other than intravenous, or when a clinician judges intravenous therapy to be appropriate because of other circumstances. Pediatric patients may receive the drug if either of the first two criteria applies.
As of October, the FDA has received safety and efficacy data on the use of peramivir for 1,891 patients with acute uncomplicated seasonal influenza A. The drug has not been evaluated in hospitalized patients. It is available from the CDC upon request by a licensed physician.
The FDA now recommends that adult patients with end-stage renal disease and a creatinine clearance of less than 10 mL/minute per 1.73 m
The updated dosing regimen for pediatric patients who have that rate of creatinine clearance but are on intermittent hemodialysis varies according to age. Such children aged 6–17 years should receive 1.6 mg/kg peramivir on day 1, followed by 1.6 mg/kg 2 hours after each hemodialysis session on hemodialysis days only.
Peramivir dosing for children who have a creatinine clearance of less than 10 mL/minute per 1.73 m
The recommendations are available at
www.flu.gov/individualfamily/prevention/medicine/antiviralsrecommend.html