Relenza (Zanamivir) – Inhalation

What Is Relenza?

Relenza (zanamivir) is a prescription option for influenza (flu) type A and B infections. People 7 years of age and older may use Relenza to treat the flu if they've had fewer than two days of symptoms. People at least 5 years of age and older can use Relenza to prevent the flu.

If you're a resident of a skilled nursing or long-term care facility, however, Relenza may not be prescribed to you since it isn't proven to be an effective preventive option in such settings. Also, this medication is not recommended for flu prevention or treatment in people with lung conditions, such as asthma or chronic obstructive pulmonary disease (COPD).

As an influenza virus neuraminidase inhibitor (NAI), Relenza works by blocking neuraminidase (NA) and preventing it from working. NA is a type of protein responsible for releasing viruses from your infected cells and encouraging the spread of the flu.

Relenza is available as a powder. You will use a Diskhaler to inhale (breath in) the powder through your mouth and into your lungs. The Food and Drug Administration (FDA) hasn't assigned any black box warnings indicating serious safety risks to Relenza.

Drug Facts

Generic Name: Zanamivir

Brand Name(s): Relenza

Drug Availability: Prescription

Therapeutic Classification: Neuraminidase inhibitor (NAI)

Available Generically: No

Controlled Substance: N/A

Administration Route: Oral (by mouth) inhalation

Active Ingredient: Zanamivir

Dosage Form(s): Powder inhalation

What Is Relenza Used For?

Relenza is used to treat or prevent the flu. Relenza, however, shouldn't be used as a replacement for the yearly flu vaccine. There's no evidence that Relenza will prevent the spread of the flu to other people.

In the United States, the flu affects up to 20% of the population yearly. The Centers for Disease Control and Prevention (CDC) estimates that the flu virus was responsible for roughly 35 million illnesses, 380,000 hospital visits, and 20,000 deaths between 2019 and 2020.

Some common symptoms of the flu include:

  • Cough
  • Body aches
  • Chills
  • Fever
  • Tiredness or weakness

How to Take Relenza

Directions might vary for different inhalers. Therefore, carefully read the directions and packaging label on the container.

In fact, your healthcare provider might recommend a bronchodilator, which might be another inhaler you use simultaneously with Relenza. If so, use your bronchodilator before Relenza. In general, bronchodilators help relax or open up the airways in your lungs. Examples of bronchodilators include the following:

  • Short-acting beta-agonists (SABA) like ProAir (albuterol)
  • Long-acting beta-agonists (LABA) like Serevent (salmeterol)
  • Long-acting muscarinic antagonists (LAMA) like Spiriva (tiotropium)

If using Relenza to treat the flu, do the following:

  • If treating the flu, you will inhale 10 milligrams (mg) of Relenza twice daily—with 12 hours in between doses.
  • If it's your first treatment day with Relenza, it's OK for doses to be less than 12 hours apart. Just make sure that you separate the doses by at least two hours.
  • You will use Relenza for five days to treat the flu.

If using Relenza to prevent the flu, do the following:

  • If you're preventing the flu, you'll inhale 10 mg of Relenza once daily.
  • If you're preventing the flu due to an outbreak in your household, you will use Relenza for 10 days. You should start Relenza within 1.5 days of when the first infected family member began to have symptoms.
  • If you're preventing the flu due to a community outbreak, you'll use Relenza for 28 days. Try to start Relenza within five days of when the community outbreak was identified.

To use the Relenza Diskhaler, do the following:

  1. Pull off the blue cover that's protecting the white mouthpiece, which should be clean when using.
  2. Pull the white mouthpiece from the inhaler until the white tray shows.
  3. Find the raised ridges and press the ridges down on both sides of the white tray while pulling the whole white tray out of the inhaler. You should now have a white tray with a dark brown wheel.
  4. Place one Rotadisk (silver medicine disk) into the dark brown wheel—with the flat side up. You'll see four lumps (blisters) on the other side of each disk. These blisters should fit into the four holes of the dark brown wheel. Each blister contains 5 mg of Relenza.
  5. Push the white tray—containing the dark brown wheel with the Rotadisk—back into the inhaler.
  6. Keep the Diskhaler level and in a horizontal position—with the "Relenza" flap facing the ceiling and the mouthpiece facing your mouth.
  7. Pull the bottom part of the "Relenza" flap up towards your face so that "Relenza" now is upside down. The flap needs to be at a 90-degree angle to the rest of the inhaler for the needle to puncture holes in the blister, containing 5 mg of Relenza medication.
  8. Now, move the "Relenza" flap back to its original position. You should hear a click, and the word "Relenza" should be facing the ceiling again.
  9. Breathe out as much air from your lungs as you can.
  10. Keeping the Diskhaler level and in a horizontal position, place the white mouthpiece in your mouth.
  11. Tightly seal your lips around the mouthpiece, but don't block the small holes on either side of the mouthpiece.
  12. Breathe in steadily and deeply through your mouth for 5 mg of Relenza to go into your lungs.
  13. Remove the inhaler from your mouth, and hold your breath for a few seconds.
  14. Keep the Diskhaler level and in a horizontal position.
  15. Pull out the white mouthpiece until the white tray is showing again but not all the way out.
  16. Once the white tray is just showing, push it back into the inhaler. You should hear a click. This pull-push motion moved the Rotadisk to the next blister.
  17. Repeat steps 6–16 to receive another 5 mg of Relenza. At this step, you should have used up two blisters for a total dose of 10 mg.
  18. Replace the blue cover to protect the white mouthpiece after each use.
  19. Once you use up all four blisters, follow steps 1–3 to remove the old Rotadisk. Afterward, continue onto steps 4 and 5 to place a new Rotadisk into the inhaler.

Storage

When you take Relenza home from the pharmacy, store it at room temperature (about 77 degrees Fahrenheit). You may expose it to temperatures of 59 degrees to 86 degrees for a short time, such as when you are traveling.

To be safe, place Relenza in a locked cabinet or closet to keep your medications out of the reach of children and pets.

Before traveling, keep in mind that the CDC recommends staying home until 24 hours after you no longer have a fever from the flu.

If you plan to travel with Relenza, get familiar with your final destination's regulations. Make a copy of your Relenza prescription. If possible, keep your medication in its original container from your pharmacy with your name on the label. If you have any questions about traveling with your medicine, ask your pharmacist or healthcare provider.

Visit the FDA's website to find out where and how to discard unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications.

How Long Does Relenza Take to Work?

Relenza may help people experience one day less of flu symptoms, including fever, cough, headache, sore throat, and muscle aches.

Many people, however, experience flu symptoms for three to seven days. Cough, tiredness, low energy, or feeling unwell may also last for more than two weeks—especially in older adults (people over 65) or people with chronic (long-term) lung conditions like COPD.

Based on this information, people using Relenza will likely experience flu symptoms for at least two to six days. Even with Relenza, some people may still experience flu symptoms for more than a week.

What Are the Side Effects of Relenza?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Some common side effects of Relenza are:

  • Cough
  • Diarrhea
  • Dizziness
  • Headaches
  • Infections of the ear, nose, and throat
  • Nausea or vomiting
  • Nose or airways irritation
  • Sinusitis (swollen sinuses)

Severe Side Effects

Get medical help right away if you experience the following serious side effects with Relenza:

  • Severe allergic reaction: If you have a severe allergic reaction to Relenza, symptoms may include breathing difficulties, itchiness, rash, and swelling.
  • Tightening of the airways: Some people might have sudden breathing problems (e.g., wheezing) with Relenza.
  • Mood or behavioral changes: Some people may experience confusion, hallucinations, seizures, speech problems, and tremors. The risk of these side effects tends to be higher in children.

Long-Term Side Effects

There is limited effectiveness and safety information on the use of Relenza beyond one five-day course for treatment or for more than 28 days of continuous use for prevention. As a result, information about long-term side effects is lacking.

Report Side Effects

Relenza may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Relenza Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For inhalation dosage form (powder):
    • For prevention of flu in a household:
      • Adults, teenagers, and children 5 years of age and older—Two puffs once a day for 10 days. Doses should be taken at the same time each day. Zanamivir must be started within 36 hours after the onset of signs and symptoms of the flu in a household.
      • Children younger than 5 years of age—Use and dose must be determined by your doctor.
    • For prevention of flu during community outbreaks:
      • Adults, teenagers, and children 5 years of age and older—Two puffs once a day for 28 days. Doses should be taken at the same time each day. Zanamivir must be started within 5 days after the outbreak was identified in the community.
      • Children younger than 5 years of age—Use and dose must be determined by your doctor.
    • For treatment of the flu:
      • Adults, teenagers, and children 7 years of age and older—Two puffs two times a day (about 12 hours apart in the morning and evening) for 5 days. Doses should be taken at the same time each day. Two doses should be taken on the first day of treatment whenever possible provided there are at least 2 hours between doses. Zanamivir must be started within 48 hours after the onset of signs and symptoms of the flu.
      • Children younger than 7 years of age—Use and dose must be determined by your doctor.
    • Canada: For treatment of flu:
      • Adults, teenagers, and children 12 years of age and older—Two puffs two times a day (about 12 hours apart in the morning and evening) for 5 days. Two doses should be taken on the first day of treatment whenever possible provided there are at least 2 hours between doses. Zanamivir must be started within 48 hours after the onset of signs and symptoms of the flu.
      • Children younger than 12 years of age—Use and dose must be determined by your doctor.

Modifications

The following modifications (changes) should be kept in mind when using Relenza:

Severe allergic reaction: Relenza powder for inhalation may contain lactose. It shouldn't be used in people with allergies to milk proteins. If you have a severe allergic reaction to Relenza or any of its ingredients, your healthcare provider should not recommend this medication.

Pregnancy: A few studies suggest Relenza isn't linked to negative effects on fetuses. However, not enough data are available to be certain. Pregnant parents, however, are at a higher risk of complications from the flu. Discuss with your healthcare provider if you are or plan to become pregnant. They will help you weigh the benefits and risks of using Relenza during your pregnancy.

Breastfeeding: In animal studies, Relenza's main ingredient, zanamivir, was present in breast milk when high intravenous (IV) doses were give to the pregnant subject. However, no significant effects were seen in offspring.

In humans, there is no information about the effects and safety of Relenza on nursing babies. High levels of Relenza are unlikely to be present in the bloodstream of nursing parents, however, suggesting a low chance of negative effects on nursing babies.

Talk to your healthcare provider if you plan to breastfeed while taking Relenza. Your healthcare provider can help you weigh the benefits and harms of using Relenza while nursing. They can also discuss the different ways available to feed your baby.

Adults over 65 years: There are no differences between older and younger adults in their responses to Relenza. There is a chance, however, that older adults may be more sensitive to Relenza's effects. As a result, use Relenza with caution.

There is no proof that Relenza is effective for flu prevention in residential facilities for older adults.

Children: The FDA approved Relenza to treat the flu in children at least 7 years old. Relenza is also FDA-approved to prevent the flu in children 5 years of age and older. Children, however, tend to have a higher risk of severe mood and behavioral changes with Relenza.

Kidney problems: Relenza hasn't been studied in people with severe kidney impairment. Since little of Relenza is absorbed into the bloodstream, dose changes aren't necessary. Caution is still recommended since there is a slight chance of buildup in the body.

Other infections: Some infections, including bacterial infections, might have similar symptoms to the flu or develop as complications of the flu. Other, coexisting conditions can also occur at the same time as the flu. Relenza isn't effective for treating or preventing such infections. Therefore, your healthcare provider may need to stop Relenza, treat the other condition, or both.

Missed Dose

If you accidentally forget your Relenza dose, use the Diskhaler as soon as you remember. If it's close to two hours until your next scheduled dose, however, then skip the missed dose and take the following dose at your next scheduled dosing time. Don't try to double up and inhale more than 10 mg at one time to make up for the missed dose.

Try to find ways to help yourself remember to routinely take your medication that works for you. If you miss multiple doses, discuss with your healthcare provider about next steps since if you miss a dose, Relenza may no longer be effective at preventing or treating the flu.

Overdose: What Happens If I Take Too Much Relenza?

Symptoms of overdose with Relenza are similar to the medication's common and serious side effects. If you think that you're experiencing an overdose or life-threatening symptoms, seek immediate medical attention.

What Happens If I Overdose on Relenza?

If you think you or someone else may have overdosed on Relenza, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Relenza, call 911 immediately.

Precautions

Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your or your child's progress after treatment. This is to make sure that the infection is cleared up completely, and to allow your doctor to check for any unwanted effects.

This medicine is not a substitute for an annual flu shot. It also will not keep you or your child from getting a bacterial infection that starts with flu-like symptoms.

Zanamivir may cause people with lung disease (e.g., chronic obstructive lung disease or asthma) to have shortness of breath, trouble breathing, or wheezing. If you have these symptoms after using this medicine, stop using this medicine and call your doctor right away.

Bronchospasm (wheezing) is a risk for patients with asthma or chronic respiratory disease. Always have a fast-acting inhaled bronchodilator available for your use.

This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Stop using this medicine and call your doctor right away if you or your child have itching, hives, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you are using this medicine.

Zanamivir may cause some people, especially children and teenagers, to be agitated, irritable, or display other abnormal behaviors, which may result in injury. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.

Make sure your doctor knows if you or your child plan to get the live nasal flu vaccine (FluMist®) before you start using this medicine. You should not receive the vaccine within two weeks before or 48 hours after using this medicine.

If your or your child's symptoms do not improve after you or your child finish taking the medicine, or if they become worse, check with your doctor.

What Are Reasons I Shouldn’t Take Relenza?

Before using Relenza, talk with your healthcare provider if any of the following applies to you:

  • Severe allergic reaction: If you have a severe allergic reaction to Relenza or any of its ingredients, avoid using it. Relenza powder for inhalation may contain lactose. It shouldn't be used in people with allergies to milk proteins.
  • Pregnancy: Small studies suggest that Relenza isn't linked to adverse effects on fetuses. However, data are limited. Pregnant parents, however, are more likely to have complications from the flu. Discuss with your healthcare provider about the benefits and risks of using Relenza during pregnancy.
  • Breastfeeding: There's no information about Relenza's effects and safety on nursing babies, but adverse events are unlikely in small, prescribed doses. Talk with your healthcare provider about the benefits and harms of using Relenza while nursing.
  • Adults over 65 years: There are no differences between older and younger adults' responses to Relenza. Since older adults may be more sensitive to Relenza's effects, caution is still recommended. Older adults may also require help when using the Relenza Diskhaler. Relenza hasn't been proven effective at preventing the flu in this setting if the older adult stays in a nursing home.
  • Children: The FDA approved Relenza to treat the flu in children at least 7 years of age. Relenza is also FDA-approved to prevent the flu in children at least 5 years and older. Children, however, might have a higher risk of severe mood or behavioral changes from Relenza.
  • Lung conditions: Relenza may cause serious side effects of tightening airways and breathing problems. Therefore, Relenza isn't recommended to treat or prevent the flu if you have a lung condition such as asthma or COPD. Relenza isn't a proven or effective flu treatment option for people with these lung conditions.
  • Other infections: Some infections, including bacterial infections, may coexist with the flu or develop as complications of the flu. Relenza isn't effective at treating or preventing these infections.
  • Flu vaccine replacement: Relenza shouldn't be used instead of getting the flu shot. There's also no evidence that Relenza can lower your risk of spreading the flu to other people.

What Other Medications Interact With Relenza?

If you plan to get the flu shot, ask for the inactivated vaccine. The inactivated vaccine doesn't have any known interaction with Relenza.

If you receive the live flu vaccine, however, there is a chance of an interaction between this vaccine and Relenza. Therefore, wait two weeks after your flu vaccine before using Relenza. If you're already using Relenza, wait two days after your last dose before getting a live flu vaccine.

Talk with your pharmacist or healthcare provider for more detailed information about medication interactions with Relenza.

And be sure to ask your healthcare provider about any other medicines you take or plan to take, including over-the-counter (OTC) products, vitamins, herbs, or plant-based medicines.

What Medications Are Similar?

The FDA approved several antiviral medications to prevent or treat the flu. The CDC, however, only recommend the following:

  • Rapivab (peramivir)
  • Relenza (zanamivir)
  • Tamiflu (oseltamivir)
  • Xofluza (baloxavir)

Compared to the other three CDC-recommended antiviral medications, Relenza 10 mg twice daily is the quickest at relieving flu symptoms. Xofluza (and then Tamiflu), on the other hand, has the lowest risk for flu-related complications. Examples of flu-related complications include other infections (e.g., bacterial pneumonia, ear infections, sinusitis) and worsening medical conditions (e.g., asthma, diabetes, heart failure).

Xofluza has the lowest risk of side effects. There's also a low chance of nausea with Relenza and vomiting with 300 mg of Rapivab. On the other hand, Tamiflu at 75 mg twice daily is linked to a higher likelihood of nausea and vomiting.

Since all of these antiviral medications are used for the flu, they're not typically used together. Talk to your pharmacist or healthcare provider if you have any questions or concerns.

Frequently Asked Questions

  • Where is Relenza available?

    Relenza is available as a prescription from your healthcare provider. Your local retail pharmacy will likely have Relenza. If necessary, the pharmacy staff will order the medication for you.

  • How much does Relenza cost?

    Relenza isn't available as a generic product yet. So, it might be costly. If cost is a concern, talk to your healthcare provider about potential financial assistance programs.

  • Can I use Relenza in my nebulizer machine?

    Relenza should only be used with the Relenza Diskhaler. The medication shouldn't be turned into a nebulizer solution.

    There are reports of hospitalized people with the flu who inhaled Relenza solutions with their nebulizer machine. Someone also passed away from using Relenza through the nebulizer machine. In this fatal case, lactose (an inactive ingredient of Relenza) clogged up the machine and prevented it from working.

How Can I Stay Healthy While Taking Relenza?

The flu can hit you very quickly, and flu symptoms may last from days to weeks. The following are some general tips on what to do if you get the flu and how to prevent the flu.

  • Get your yearly flu vaccine.
  • Take flu-related medications as recommended by your healthcare provider.
  • Cover your face when sneezing or coughing.
  • Wash your hands with soap and water ofen.
  • Avoid touching your eyes, nose, and mouth with your hands.
  • Clean high-touch surfaces and objects, such as doorknobs, light switches, and tables
  • Keep your distance if you or someone else has the flu.
  • Stay home—except for medical-related visits—if you have the flu. You should stay home until 24 hours after you no longer have a fever.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Relenza label.

  2. National Center for Complementary and Integrative Health. Flu and colds: in depth.

  3. Centers for Disease Control and Prevention. Influenza (flu): disease burden of flu.

  4. National Institute on Aging. Flu and older adults.

  5. Centers for Disease Control and Prevention. Influenza (flu): preventative steps.

  6. Centers for Disease Control and Prevention. Influenza (flu): clinical signs and symptoms of influenza.

  7. Lactmed. Zanamivir.

  8. MedlinePlus. Zanamavir oral inhalation.

  9. Food and Drug Administration. Influenza (flu) antiviral drugs and related information.

  10. Liu JW, Lin SH, Wang LC, et al. Comparison of antviral agents for seasonal influenza outcomes in healthy adults and children. JAMA Network Open. 2021;4(8):e2119151. doi: 10.1001/jamanetworkopen.2021.19151.

  11. Centers for Disease Control and Prevention. Influenza (flu): key facts about influenza (flu).

  12. Food and Drug Administration. Orange book: approved drug products with therapeutic equivalence evaluations.

  13. Centers for Disease Control and Prevention. Influenza (flu): healthy habits to help protect against the flu.

  14. Centers for Disease Control and Prevention. Flu: what to do if you get sick.

By Ross Phan, PharmD, BCACP, BCGP, BCPS
Ross is a writer for Verywell with years of experience practicing pharmacy in various settings. She is also a board-certified clinical pharmacist and the founder of Off Script Consults.