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Generic Name: Zanamivir
Product Name: Relenza


Relenza is used to:

  • Treat adults and children five years or older who are infected with influenza virus strains of type A or B. Individuals should begin Relenza treatment within 48 hours of the onset of flu symptoms.
  • Prevent the transmission of influenza A and B viruses during outbreaks of new strains of these viruses for which no vaccine exists (e.g. bird flu, swine flu). The medicine is not used for prevention purposes in general influenza outbreaks.
FluFor more information on the common cold and influenza, types of influenza and treatments and tips for preventing influenza, see Cold and Flu.


The active ingredient in Relenza is zanamivir, a type of medication known as a neuraminidase inhibitor.

Neuraminidase is an enzyme that works on the surface of influenza virus cells. It helps transfer newly formed virus particles from infected cells to healthy cells, thus helping influenza to replicate and spread through the body. Influenza virus replication takes place in the epithelium of the respiratory tract.

Relenza is orally inhaled so that the medication enters the respiratory tract, where it inhibits the action of neuraminidase, effectively blocking the virus replication process.

Dose advice

Dose information

Relenza is administered by oral inhalation in a similar manner to asthma medications which are inhaled through a puffer. A special inhaling device known as the diskhaler is provided with the medication.


For treatment of influenza infection, the doctor will usually prescribe 2 x 5 mg inhalations (total 10 mg inhalation) to be taken twice a day (i.e. total of 20 mg inhalation daily). The medication is usually prescribed for a period of five days. Treatment should commence as soon as possible and within 48 hours of the onset of influenza symptoms.


For prevention of influenza infection during outbreaks, the doctor will usually prescribe 2 x 5 mg inhalations (total 10 mg inhalation) once a day. For preventative purposes, Relenza should be administered for at least 10 days, and for up to 28 days if risk of influenza exposure remains high.

For further information about the appropriate Relenza dose or the correct way to take the medication, speak to your doctor.


Relenza should not be taken by individuals who experience hypersensitivity reactions to lactose (e.g. dairy products) or zanamivir.


Relenza may exacerbate respiratory (e.g. asthma) or neuropsychic (e.g. hallucinations) symptoms in some patients who already experience them. Tell your doctor if you have a respiratory or neuropsychic condition so that these conditions can be taken into account when deciding on the most appropriate course of treatment.

Use in pregnancy

Relenza is a Pregnancy Category B1 medication. Relenza has not been established as safe to use during pregnancy.

Use in lactation

Relenza has not been established as safe to use during breastfeeding.

Patient advice

Patients using bronchodilators to control respiratory conditions should inhale these medications immediately before taking Relenza.


Relenza is Schedule 4.1

Common side effects

All medicines have side effects. Most commonly the side effects are minor; however, some can be more serious. Usually the benefits of taking a medication outweigh the associated side effects. Your doctor would have considered these side effects before starting you on Relenza.

The side effects of zanamivir treatment all occur very rarely (i.e. in less that 0.01% of treated patients). These side effects are:


  1. Prescribing Information: Zanamivir [online]. MIMS Online. March 2008 [cited 2 May 2009]. Available from: [URL Link]
  2. Zanamivir [online]. Australian Medicines Handbook Online. January 2009 [cited 2 May 2009]. Available from: [URL Link]

For further information talk to your doctor.

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Posted On: 22 July, 2003
Modified On: 7 May, 2010
Reviewed On: 14 May, 2009


Created by: myVMC