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Generic name: zanamivir
Drug classes: Inhaled anti-infectives, Neuraminidase inhibitors

Medically reviewed by  A Ras MD.

What is Relenza?

Relenza is a prescription medicine used to treat the flu (influenza A and B virus) in people who are aged 7 years and older who have had flu symptoms for no more than 2 days. It is also used to help prevent the flu in people who are aged 5 years and older.

Relenza is not recommended for the treatment or prevention of the flu in people with breathing problems, such as asthma and chronic obstructive pulmonary disease (COPD).

Relenza does not treat or prevent illness that is caused by infections other than the influenza virus (A and B).

Using Relenza for the treatment of the flu has not been shown to reduce the risk of spreading the flu to others.

It is not known if Relenza is:

  • effective for the treatment of flu in people with breathing problems.
  • effective for the prevention of flu in people who live in nursing homes.
  • safe and effective for the treatment of flu in children younger than 7 years.
  • safe and effective for the prevention of flu in children younger than 5 years.

Relenza does not take the place of receiving a flu vaccination. Talk to your healthcare provider about when you should receive an annual flu vaccination.


The active component of RELENZA is zanamivir. The chemical name of zanamivir is 5-(acetylamino)-4-[(aminoiminomethyl)-amino]-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-galacto-non-2-enonic acid. It has a molecular formula of C12H20N4Oand a molecular weight of 332.3. It has the following structural formula:

zanamivir structural formula

Zanamivir is a white to off-white powder for oral inhalation with a solubility of approximately 18 mg/mL in water at 20°C.

RELENZA is for administration to the respiratory tract by oral inhalation only. Each RELENZA ROTADISK contains 4 regularly spaced double-foil blisters with each blister containing a powder mixture of 5 mg of zanamivir and 20 mg of lactose (which contains milk proteins). The contents of each blister are inhaled using a specially designed breath-activated plastic device for inhaling powder called the DISKHALER.

After a RELENZA ROTADISK is loaded into the DISKHALER, a blister that contains medication is pierced and the zanamivir is dispersed into the air stream created when the patient inhales through the mouthpiece. The amount of drug delivered to the respiratory tract will depend on patient factors such as inspiratory flow. Under standardized in vitro testing, RELENZA ROTADISK delivers 4 mg of zanamivir from the DISKHALER device when tested at a pressure drop of 3 kPa (corresponding to a flow rate of about 62 to 65 L/minute) for 3 seconds.

Who should not take Relenza?

Do not take Relenza if you are allergic to zanamivir or any other ingredient of Relenza, including milk proteins. See the end of this Patient Information guide for a complete list of ingredients in Relenza.

What should I tell my healthcare provider before taking Relenza?

Before taking Relenza, tell your healthcare provider about all of your medical conditions, including if you:

  • have any breathing problems, such as asthma or COPD.
  • received live attenuated influenza vaccine (LAIV) in your nose (intranasal) in the past 2 weeks.
  • are pregnant or plan to become pregnant.
  • are breastfeeding or plan to breastfeed. It is not known if Relenza passes into your breast milk.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

How should I take Relenza?

Read the Instructions for Use that come with Relenza for detailed information on how to take Relenza.

  • Take Relenza exactly as your healthcare provider tells you to.
  • Relenza is taken by oral inhalation using a Diskhaler.
  • If you are scheduled to use an inhaled bronchodilator at the same time as Relenza, use the inhaled bronchodilator before taking Relenza.
  • Each dose of Relenza requires 2 inhalations. Each inhalation requires 1 blister.

For the treatment of flu in people aged 7 years and older, take Relenza as follows:

  • Take each dose of Relenza as 2 inhalations (use 1 blister per inhalation) 2 times a day for 5 days.
  • On the first day, wait at least 2 hours between each dose.
  • Starting on the second day, wait at least 12 hours between each dose.

To help prevent the flu in people aged 5 years and older, take Relenza as follows:

  • Take each dose of Relenza as 2 inhalations (use 1 blister per inhalation) 1 time each day for 10 or 28 days as prescribed by your healthcare provider.
  • Take Relenza at the same time each day.

If you miss a dose of Relenza, take it as soon as you remember. If it is 2 hours or less before your next dose, do not take the missed dose. Take your next dose of Relenza at your scheduled time. Do not take 2 doses at the same time.

What are the possible side effects of Relenza?

Relenza can cause serious side effects, including:

  • Bronchospasm (wheezing). Serious breathing problems, including death, have happened during treatment with Relenza in people with and without a history of breathing problems. 41TStop taking Relenza and get emergency medical help right away if you develop:
    • worsening breathing
    • shortness of breath
    • chest pain or tightness
    • cough
  • If you have breathing problems, such as asthma and COPD and your healthcare provider has prescribed Relenza, you should have a fast‑acting, inhaled bronchodilator available for your use. See “How should I take Relenza?”
  • Serious allergic reactions. Relenza can cause serious allergic reactions. Stop taking Relenza and get emergency medical help right away if you get any of the following symptoms:
    • skin rash or hives
    • your skin blisters and peels
    • blisters or sores in your mouth
    • itching
    • swelling of your face, eyes, lips, tongue, or throat
    • trouble breathing
    • chest pain or tightness
  • Change in behavior. People, especially children, who have the flu, can develop nervous system problems and abnormal behavior that can lead to death. During treatment with Relenza, tell your healthcare provider right away if you or your child have confusion, speech problems, shaky movements, seizures, or start hearing voices or seeing things that are not really there (hallucinations).

The most common side effects of Relenza include:

Other kinds of infections can appear like flu or happen along with flu, and may need different kinds of treatment. Call your healthcare provider if you feel worse or develop new symptoms during or after treatment with Relenza, or if your flu symptoms do not start to get better.

These are not all of the possible side effects of Relenza.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1‑800‑FDA‑1088.

General information about the safe and effective use of Relenza

Medicines are sometimes prescribed for purposes other than those listed in a Patient Information leaflet. Do not use Relenza for a condition for which it was not prescribed. Do not give Relenza to other people, even if they have the same symptoms that you have. It may harm them. You can ask your healthcare provider or pharmacist for information about Relenza that is written for health professionals.

How should I store Relenza?

  • Store Relenza at room temperature below 77°F (25°C).
  • Do not puncture any Relenza Rotadisk blister until you are ready to take your dose using the Diskhaler.

Keep Relenza and all medicines out of the reach of children.

What are the ingredients in Relenza?

Active ingredient: zanamivir

Inactive ingredients: lactose (which contains milk proteins)



  • NDC 0173-0681-01
  • 20 mg per Rotadisk
  • (5 mg per blister)
  • Each blister contains 5 mg zanamivir with lactose.
  • Use RELENZA with DISKHALER inhalation device only.
  • See enclosed “Patient Information” and “Patient Instructions for Use.”
  • Store at 25oC (77oF); excursions permitted to 15o to 30oC (59o to 86oF) (see USP Controlled Room Temperature).
  • Contains 5 RELENZA ROTADISKS® each containing four 5-mg blisters and one DISKHALER inhalation device.
  • Rx only
Relenza carton


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