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Flu (Influenza) MedicationsImportant Information
The flu (influenza) is an illness caused by different influenza viruses. It attacks mainly the upper respiratory tract - the nose, throat, and rarely the lungs. The flu is characterized by sudden onset of high fever, body aches, chills, fatigue, headache, severe malaise, cough, sore throat, and runny nose. The first flu virus was identified in the 1930s. There are three types of influenza virus: A, B, and C. Types A and B are the most severe. The viruses change constantly and different strains circulate around the world every year. Type C causes either a very mild illness, or has no symptoms at all. It does not cause epidemics and does not have the severe public health impact that influenza types A and B do. Flu antiviral medications are prescription drugs used for prevention or treatment of flu viruses. They work by decreasing the ability of flu viruses to reproduce. For flu treatment, antiviral drugs should be started within 2 days after illness onset. When used correctly, these medications can reduce the severity of symptoms and shorten the duaration of flu attack by 1 or 2 days. They may also prevent flu complications. When used for flu prevention, antiviral drugs are about 70-90% effective against susceptible viruses. There are 4 antiviral drugs approved by the FDA for treating flu: amantadine, rimantadine, zanamivir and oseltamivir. Amantadine and rimantadine are active only against influenza A. Zanamivir and oseltamivi are members of a new class of flu antivirals that act against both influenza types A and B. Flu medications include:
These four drugs differ in pharmacokinetics, side effects, approved age groups, dosages, and costs.
Amantadine and rimantadine, known as adamantanes or M2 inhibitors, have been used as first-choice antiviral medications against influenza A viruses for many years. However, high rates of drug resistance among influenza A viruses deplete the adamantanes usefulness. These antiviral drugs inhibit the activity of the influenza virus M2 protein, which forms a channel in the virus membrane. As a result, the virus cannot make copies of itself after it enters a cell. Amantadine and rimantadine have comparable effectiveness in treating or prevention influenza A. However, rimantadine has lower potential for causing central nervous system side effects than amantadine.
A second class of antiviral drugs for influenza is the neuraminidase inhibitors, which includes oseltamivir (Tamiflu) and zanamivir (Relenza). These drugs work on a broader spectrum of influenza strains and have activity against both influenza A and B viruses. Neuraminidase is an enzyme that helps release new virus particles from infected cells. Neuraminidase inhibitors block the action of neuraminidase thereby preventing the release of new copies from infected cells. By preventing the spread of virus from cell to cell, the symptoms and duration of flu infection are reduced. Antiviral flu drugs are most effective when given within 48 hours of the onset of illness. They can decrease the duration of the disease by 1 to 2 days if used within this early time period. They are usually given for a period of about 5-7 days. Oseltamivir (Tamiflur), the most important antiviral drug, is available as capsules and oral suspension. The primary side effects associated with oseltamivir use are nausea and vomiting. There are some concerns that oseltamivir may cause psychological and neuropsychiatric side effects. Zanamivir (Relenza) is an inhaled powder that comes with a device called Diskhaler. The most common side effects with zanamivir include diarrhea, nausea, nasal symptoms, cough, and headache. Also, zanamivir should not be used in people with asthma or other chronic lung disease. These drugs are expensive and currently not available for use in many countries. References
Last updated: October, 2009 |
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In response to requests from the US Centers for Disease Control and Prevention, US FDA authorized emergency use of Roche