Medications
For mild influenza, symptom relief is similar to that for colds. Vaccines are available to prevent influenza (See section on Viral Influenza Vaccines).
Two classes of antiviral agents have been developed to treat influenza A, B, or both: M2 inhibitors and neuraminidase inhibitors. The CDC recommended in January 2006 that the M2 inhibitors should no longer be used to treat flu during the 2005 – 2006 season because many strains of influenza A have become resistant to these drugs. M2 inhibitors have never been active against influenza B, a milder infection. Until recently, these agents were considered appropriate for prevention and treatment of the flu.
Anti-Viral Drugs: M2 Inhibitors
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Brands and Benefits. Amantadine (Symmetrel) and rimantadine (Flumadine) are M2 inhibitors. They have the following benefits against drug-sensitive strains of influenza A:
- Both offer protection against influenza A and prevent severe illness if a person contracts the infection. (To be effective it must be administered within 2 days of onset.)
- They may shorten the duration and lessen the severity of the flu if given within 48 hours of onset of symptoms.
Limitations. Drawbacks of M2 inhibitors include:
- Viral resistance to these agents is rapidly emerging. For this reason, the CDC now recommends that M2 inhibitors should not be used during the 2005 – 2006 flu season in the U.S.
- M2 inhibitors are not effective against influenza B.
- Neither has proven to reduce the risk for complications, including pneumonia and bronchitis.
Side Effects. Both agents occasionally cause nausea, vomiting, indigestion, insomnia, and hallucinations. Amantadine affects the nervous system and about 10% of people experience nervousness, depression, anxiety, difficulty concentrating, and lightheadedness. Rimantadine is less likely to do so. Rarely, amantadine can cause seizures, usually in elderly people already at risk for psychiatric symptoms.
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