January 2006
For Immediate Release

Interim Recommendation for Use of Amantadine for Influenza

The Public Health Agency of Canada is recommending that health care providers in Canada not prescribe amantadine to treat and prevent influenza during the current flu season. The interim recommendation follows testing showing viruses currently in circulation are resistant to the drug.

The Agency's National Microbiology Laboratory in Winnipeg tested 47 influenza A/H3N2 isolates and found that 43 (91%) are resistant to amantadine, an antiviral recommended by the National Advisory Committee on Immunization (NACI) to prevent and control influenza outbreaks in institutions, such as long term care facilities. The samples tested were collected from four provinces - British Columbia, Ontario, Saskatchewan and Alberta - since September, 2005.

The results represent a significant increase in resistance compared to previous years and are consistent with the level of antiviral resistance recently reported by the Centers for Disease Control and Prevention (CDC) in the United States.

At this time, oseltamivir (Tamiflu) or zanamivir (Relenza) should be selected if an antiviral medication is recommended for the treatment or prevention of influenza for the remainder of the 2005/2006 influenza season. Testing conducted by the CDC indicates oseltamivir remains effective against the H3N2 virus.

Testing of influenza isolates for the 2005-2006 season will continue and recommendations will be updated based on results.

The results are an important reminder that antiviral medications - which don't provide immunity - should not replace annual influenza immunization for the prevention of influenza. Influenza immunization - or the annual "flu shot" - remains the most effective method of avoiding contracting influenza when combined with proper hygiene, including frequent hand washing and staying home when you are ill.

This year's influenza vaccine includes a strain similar to the H3N2 virus, providing immunity to those who received the flu shot this season.

Surveillance data indicates influenza-like illness this season is within normal ranges with no widespread influenza activity reported in any province or territory. There have been 10 outbreaks of influenza reported in long term care facilities reported to the Agency since the beginning of the flu season in September.