Adamantanes: Amantadine and rimantadine have activity against influenza A but not B viruses.
- Both are approved for use as chemoprophylaxis to prevent influenza. They are 70-90% effective in limiting the infection to subclinical levels so that the body still has a protective immune response and develops antibodies for circulating influenza viruses. However, the use of chemoprophylaxis is limited. Those who should consider it include:
- People at high risk for serious influenza disease who were not vaccinated before a local outbreak.
- Health care providers for people at high risk
- Severely immunocompromised persons (including HIV disease, transplant patients, and cancer therapy recipients).
- The elderly
Neuraminidase inhibitors: Zanamivir (Relenza) and oseltamivir (Tamiflu)
- Relenza is the brand name for the drug zanamivir, developed by GlaxoSmithKline (http://www.gsk.com/index.htm).
- It is an antiviral medication that works by inhibiting the neuraminidase protein of Influenza A and B viruses, effectively blocking the release of virus from infected cells, and therefore limiting viral spread from one cell to another.
- The FDA has approved Relenza for the treatment of uncomplicated influenza virus infection for persons of 7 years and older.
- It is effective against both type A and B influenza provided that patients begin treatment within 48 hours of the onset of symptoms.
- Relenza is administered as a powder, inhaled through a Diskhaler device twice a day for five days after illness onset.
- The most common side effect is bronchospasm (wheezing). Relenza is therefore not typically recommended for people with chronic respiratory disease.
- The FDA has not yet approved Relenza for chemoprophylactic use, though studies done in nursing homes indicate that it is 84% effective in prevention of influenza disease.
- Treatment with Relenza does not appear to antagonize immune response to influenza vaccine, but should not be used as a substitute for the vaccine.
- Please refer to the U.S. Food and Drug Administration’s Center for Drug Evaluation and Research for more information: http://www.fda.gov/cder/news/relenza/default.htm"
- Tamiflu is the brand name for the drug Oseltamivir phosphate ( http://www.tamiflu.com/)
- Like Relenza it is able to block the release of virus progeny by binding to the neuraminidase protein. http://www.tamiflu.com/consumer_howitworks.asp
- It was FDA approved in October 27, 1999.
- It is effective against Influenza A and B.
- Tamiflu is taken orally in a grey/light yellow capsule or in Powder for Oral Suspension.
- Tamiflu's safety and effectiveness on immunocompromised individuals has not been tested.
- For more information please refer to U.S. Food and Drug Administration’s Center for Drug Evaluation and Research: http://www.fda.gov/cder/consumerinfo/druginfo/tamiflu.htm
For more information on drug therapy for influenza virus, please visit the CDC’s website: http://www.cdc.gov/flu/professionals/treatment/0506antiviralguide.htm