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What Is Relenza?


Updated November 03, 2010

What Is Relenza?

Relenza, an antiviral medication to treat or prevent the flu

Photo © GlaxoSmithKline

Relenza (zanamavir) is an antiviral drug used to prevent or shorten the duration of the flu (influenza). It is an inhaled powder medication that is typically taken twice a day for five days to treat the flu or once a day for up to 28 days to prevent it for those people living with someone who has the flu or at high risk during a community outbreak.

Although Relenza is available to shorten the duration of or help prevent the flu, the best way to prevent the flu is to get a flu shot every year. It is much more effective and has far fewer side effects than antiviral medications. However, Relenza and other antiviral medications can be helpful to those who cannot get a flu shot or may need a second line of defense against the flu.

When to Take Relenza:

Relenza should be taken within two days of the onset of symptoms from the influenza virus. Only your healthcare provider can determine if you are actually suffering from the flu or something else. Relenza will only be effective if started within 48 hours of the onset of symptoms.

Who should take Relenza:

Relenza is approved to shorten the duration of the flu in adults and children over the age of 7 and is approved to prevent the flu in adults and children over the age of 5.

Who should not take Relenza:

Relenza is not recommended for people with chronic lung problems, such as asthma or chronic obstructive pulmonary disorder (COPD). It has not been proven to shorten the duration of the flu in these patients and is not recommended for anyone with these conditions.


  • Relenza may cause serious breathing problems in people with chronic lung diseases such as asthma.
  • Some people, mostly children and adolescents, who have the flu and are taking Relenza have had serious psychological or neurological side effects. These may include confusion, anxiety, seizures, hallucinations or even suicide. If your child who is taking Relenza starts behaving abnormally, notify his healthcare provider immediately.

Side Effects:

Some common side effects of Relenza include:

  • Dizziness
  • Irritation of the Nose
  • Joint pain

If these symptoms become irritating or do not go away, contact your healthcare provider.

More serious side effects of Relenza include:

  • Difficulty breathing
  • Wheezing
  • Shortness of breath
  • Hives
  • Rash
  • Itching
  • Difficulty Swallowing
  • Hoarseness
  • Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles or lower legs

If you experience any of these symptoms while taking Relenza, seek medical attention immediately.

Important Info to Share With Your Healthcare Provider

Be sure to tell your healthcare provider:

  • If you are pregnant, planning to become pregnant, breastfeeding or become pregnant while taking Relenza.
  • If you are allergic to Relenza, any other medications, foods or lactose.
  • If you have asthma, other breathing problems, bronchitis, emphysema, heart, liver, kidney or other lung diseases.
  • Any other medications or herbal supplements you may be taking. Your doctor may need to adjust your doses so they are still effective while you are taking Relenza.


”Patient Information Sheet: Zanamavir (marketed as Relenza).” FDA/Center for Drug Evaluation and Research 10 Mar 08. 30 May 08.

”Zanamavir Inhalation.” National Institutes of Health 01 May 08. Department of Health and Human Services. 01 June 08.

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