Pan-canadian public health network council report and policy recommendations on the use of antivirals for prophylaxis during an influenza pandemic

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Background and Current Status of Antivirals in Canada

At the time of publication of the 2004 edition of the CPIP, the use of antivirals as part of a comprehensive pandemic response had been discussed at the technical level but the National Antiviral Stockpile (NAS) had not been created. Therefore, the guidance provided in the Antivirals Annex at that time was directed towards those involved in pandemic planning and specifically the health sector response. The provision of a list of priority indications for antivirals during a pandemic was intended to give planners an opportunity to consider how they might access and administer antivirals to specific groups, such as health care workers and high risk groups.

After the decision to create a NAS was made in 2004, the previously published priority indications were reviewed. When the adequacy of the initial 16 million dose stockpile was revisited in 2006, and the decision was made to increase the size of the stockpile, a focus on a population-based treatment strategy, based on scientific and logistical considerations, was recommended. At that time, it also was determined that there was a need for a thorough examination of the issue of whether to include prophylactic indications in the Antiviral Strategy.

The National Antiviral Stockpile (NAS) is currently limited to the neuraminidase inhibitors oseltamivir (Tamiflu^®) and zanamivir (Relenza^®). Amantadine, a lower-cost generic antiviral drug, which is not a neuraminidase inhibitor, has also been used to treat and prevent influenza in Canada and elsewhere. However, concerns regarding its antiviral resistance, dosage logistics, and adverse event profile have led the Pandemic Influenza Committee (PIC) to endorse the recommendation of its Antiviral Working Group that this drug not be included in the NAS. TGAP’s further examination of amantadine is reported under Scientific Considerations (Section C-1 of the Report).

Tamiflu^® and Relenza^® a can be prescribed for both treatment and prophylaxis (prevention). There are two types of prophylaxis. Post-exposure prophylaxis means taking a daily dose of medication for 10 days following close contact with an infected individual. Pre-exposure prophylaxis means taking a daily dose of medication for a number of weeks prior to expected exposure. Tamiflu^® is not approved for pre-exposure prophylaxis in Canada and studies done on this have been for short periods only.

There is currently little use of these prescription drugs in Canada for seasonal influenza. The main use of Tamiflu^® at this time is to control long-term care (LTC) facility outbreaks, when it is prescribed for both treatment and post-exposure prophylaxis.

A key operational issue, regarding the use of the NAS for early treatment of pandemic influenza, is that an implementation strategy has not yet been fully developed.

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