In its "Take Three Actions to Fight the Flu" campaign, the Centers for Disease Control and Prevention lists prescription antiviral drugs as the third and last line of defense against influenza. Although most people with influenza don't need them, according to the CDC, there are several notable exceptions. The elderly, children under 5, women who are pregnant and up to two weeks postpartum and people with other kinds of medical problems should contact their health-care providers as soon as symptoms appear. As of May 2010, the FDA has approved two antiviral drugs, Tamiflu and Relenza, for the treatment and prevention of influenza.
Mechanism of Action
Tamiflu and Relenza are classified as "neuraminidase inhibitors" because, according to a 2009 article in the British Medical Journal, they inhibit the enzyme neuraminidase that helps the influenza virus spread from cell to cell. As a result, the virus is confined to just a few cells, limiting or preventing symptoms. According to the CDC, patients should begin therapy as soon as possible after symptoms appear and sometimes even before. Taken within 48 hours of symptoms onset, antivirals decrease symptom severity and shorten the duration of disease by one or two days. Taken before the onset of symptoms, antivirals can prevent a person from ever getting sick in the first place.
Tamiflu Prescribing Information
Tamiflu (oseltamivir phosphate) is dispensed as 30, 45 or 75mg capsules or a 12mg/mL oral suspension suitable for children and others who might have problems swallowing capsules. Tamiflu is FDA-approved for the treatment of influenza in people of all ages, including infants. The most common side effect is upset stomach, which can be avoided by taking the drug with food.
Relenza Prescribing Information
Relenza (zanamivir inhalation) is dispensed as a 5mg "rotadisk," which is powder-filled blister inhaled through the mouth using an included plastic device called a "diskhaler." Patients who have not used Relenza before should ask their pharmacist for help using the device. Relenza is FDA-approved for the treatment of influenza in people older than 7. Relenza sometimes causes airway spasms, so it should not be taken by people with a history of underlying heart or lung disease.
References
- British Medical Journal; "Neuraminidase Inhibitors for Preventing and Treating Influenza in Healthy Adults: Systematic Review and Metaanalysis"; T. Jefferson, M. Jones, P. Doshi, and C. Del Mar; 2009
- GlaxoSmithKline: Relenza Prescribing Information
- Tamiflu: Tamiflu Prescribing Information
