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Relenza

Generic name: zanamivir [ zan-AM-i-vir ]
Drug classes: Inhaled anti-infectives, Neuraminidase inhibitors

Medically reviewed by Drugs.com. Last updated on Oct 12, 2023.

What is Relenza?

Relenza is an antiviral medicine that blocks the actions of viruses in your body.

Relenza is used to treat flu symptoms caused by influenza virus in people who have had symptoms for less than 2 days.

Relenza may also be given to prevent influenza in people who may be exposed but do not yet have symptoms. Zanamivir will not treat the common cold.

Relenza should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Warnings

Some people using Relenza have had sudden unusual changes in mood or behavior, most often in children. It is not certain that zanamivir is the exact cause. Even without using zanamivir, anyone with influenza can have neurologic or behavioral effects that may lead to confusion or hallucinations. Call your doctor right away if the person using this medicine has any signs of unusual thoughts or behavior.

Relenza should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Before using Relenza, tell your doctor if you have asthma, chronic obstructive pulmonary disease (COPD), or any other chronic lung condition. Serious or life-threatening bronchospasm (difficulty breathing) and other effects on the lungs can occur while using this medicine. Stop using Relenza and call your doctor at once if you have wheezing or severe breathing problems. Do not use a nebulizer or ventilator to give this medicine. The inhalation powder should never be mixed with a liquid.

Treatment with this medicine should start as soon as possible when flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Do not use an inhaled nasal flu vaccine (FluMist) within 2 weeks before or 48 hours after using this medicine. Zanamivir may interfere with the drug action of FluMist, making the vaccine less effective. Follow your doctor's instructions.

Before taking this medicine

You should not use Relenza if you are allergic to zanamivir or to lactose (milk sugar).

Do not use Relenza to treat flu symptoms in a child younger than 7 years old. Children as young as 5 years old may use the medication to prevent flu symptoms.

To make sure Relenza is safe for you, tell your doctor if you have ever had:

It is not known whether this medicine will harm an unborn baby. However, getting sick with influenza during pregnancy can cause complications leading to birth defects, low birth weight, preterm delivery, or stillbirth. Your doctor will decide whether you should use zanamivir if you are pregnant.

The Centers for Disease Control and Prevention (CDC) recommends that pregnant women may receive a yearly flu vaccine to prevent influenza. Relenza is not to be used in place of the yearly flu shot.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Relenza pregnancy and breastfeeding warnings (more detail)

How should I use Relenza?

Use Relenza exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Start taking Relenza as soon as possible after flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Relenza is packaged in disk-shaped foil packs that contain 4 blisters of medicine. Each blister contains a dose of zanamivir in a powder form. These disks are placed into a device called a DISKHALER that you will use to inhale the medicine. The device opens and loads a blister each time you use the inhaler.

To treat flu symptoms: Use 2 inhalations twice per day for 5 days. On the first day of treatment, space your doses at least 2 hours apart. On the following days, space your doses at least 12 hours apart.

To prevent flu symptoms: Use 2 inhalations every 24 hours for 10 to 28 days. Follow your doctor's instructions.

Do not use a nebulizer or ventilator to give this medicine. Relenza inhalation powder should never be mixed with a liquid.

If you are scheduled to use a bronchodilator at the same time as Relenza, use the bronchodilator first.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Call your doctor if your symptoms do not improve, or if they get worse.

Store at room temperature away from moisture and heat. Throw away the DISKHALER after your treatment ends.

Dosing information

Usual Adult Dose for Influenza:

10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Adult Dose for Influenza Prophylaxis:

10 mg (2 inhalations) inhaled orally once a day

Duration:
Household setting: 10 days
Community outbreak: 28 days

Usual Pediatric Dose for Influenza:

7 years or older: 10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Pediatric Dose for Influenza Prophylaxis:

5 years or older: 10 mg (2 inhalations) inhaled orally once a day

Duration:
Household setting: 10 days
Community outbreak: 28 days

Detailed Relenza dosage information

What happens if I miss a dose?

Use the medicine as soon as you can, but skip the missed dose if your next dose is due in less than 2 hours. Do not use two doses at one time.

Call your doctor if you miss several doses.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using Relenza?

Do not use a nasal flu vaccine (FluMist) within 48 hours after taking Relenza. This medicine may interfere with the drug action of FluMist, making the vaccine less effective. Follow your doctor's instructions.

Relenza side effects

Get emergency medical help if you have signs of an allergic reaction to Relenza: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some people using Relenza (especially children) have had sudden unusual changes in mood or behavior. It is not certain that zanamivir is the exact cause of these symptoms. Even without using Relenza, anyone with influenza can have neurologic or behavioral symptoms. Call your doctor right away if the person using this medicine has:

Stop using this medicine and call your doctor at once if you have wheezing or severe breathing problems, or if you feel like you might pass out.

Common Relenza side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Relenza side effects (more detail)

What other drugs will affect Relenza?

Other drugs may interact with zanamivir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Relenza drug interactions (more detail)

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Relenza only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

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