Australian Health Management Plan for Pandemic Influenza (2009)

Appendix G: Antivirals

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The pandemic planning assumptions, relevant to the use of antivirals, are outlined in Part 3.

They include:

• Assumption Table 10: Treatment with Neuraminidase Inhibitor (NI) antivirals
• Assumption Table 11: Antiviral prophylaxis with Neuraminidase Inhibitor (NI) antivirals.

Summary of current antiviral policy

This plan describes a flexible policy for the use of antivirals. The detail of the high level policy described below may be modified at the time as evidence comes in about a range of factors, such as:

• the effectiveness of antivirals in preventing infection and treating cases (including any evidence of antiviral resistance)
• the effectiveness of candidate and customised pandemic vaccine
• the protection offered by natural infection
• the availability of resources
• the anticipated length of time until the customised pandemic vaccine will become available.

Antiviral usage

Antiviral usage includes:

• treatment of cases when clinically appropriate
• post-exposure prophylaxis to reduce the risk of infection in people who have not been able to avoid close unprotected contact with an infectious case, such as:
  • in health care and some other occupational settings
  • in households
  • in the community (e.g. workplace) in the CONTAIN phase.
• pre-exposure prophylaxis to reduce the likelihood of infection when:
  • persons are exposed to an aerosol generating procedure on a case
  • there is likely to be ongoing re-exposure to known infectious cases for example, in influenza services.

If MAINTENANCE phase is ever encountered, the policy on the use of antivirals may include the need to maintain functioning of critical infrastructure. This decision would be made at a whole of government level by the Australian Government in consultation with state and territory governments.

Depending on resource availability the Australian Government will consider reserving some stocks of antivirals for a possible second wave.

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Antivirals that are mostly likely to be used for pandemic influenza

There are currently three antiviral medicines registered for influenza use in Australia. They are:

• Oseltamivir (brand name: Tamiflu) that is swallowed either as a capsule or suspension made up from dried powder. Oseltamivir is registered in Australia for both treatment and prevention of influenza in patients over the age of 12 months.
• Zanamivir (brand name: Relenza) that is given as an inhaled powder. It is registered in Australia for both treatment and prevention of influenza in patients aged five years or older.
• Amantadine (brand name: Symmetrel) that is given as a tablet. It is registered in Australia for influenza treatment by patients aged five years or older.

Oseltamivir and zanamivir (which are in the same class of drugs namely neuraminidase inhibitors) are thought to have relatively few side effects and are tolerated well. Amantadine has a number of side effects that make its use, particularly in older people, less well tolerated. However, as amantadine works through a different mechanism to oseltamivir and zanamivir, this drug has been stockpiled to allow its use if circumstances arise that may make this drug (either alone or in combination) the treatment of choice for certain individuals.

Delirium has been reported during oseltamivir administration in patients with influenza, predominately in children and adolescents. The contribution of oseltamivir to those events is unknown; however, patients with influenza should be closely monitored for signs of abnormal behaviours through the treatment period.

A number of other newer antiviral medications are currently undergoing clinical trials. Their development is being monitored.

Details of dosage and side effects can be found in the Interim National Pandemic Influenza Clinical Guidelines (June 2006) and Primary Care Annex. Information on adverse event reporting and monitoring of effectiveness is outlined in the Surveillance Annex.

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This information is current for 19 May, 2013
This information was issued on 01 November, 2010