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.

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.

Brand Name(s): Relenza

Therapeutic Classification: Neuraminidase inhibitor (NAI)

Controlled Substance: N/A

Administration Route: Oral (by mouth) inhalation

Dosage Form(s): Powder inhalation

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:

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:

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

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

To use the Relenza Diskhaler, do the following:

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.

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.

Currently, Relenza doesn't have any off-label uses.

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.

Some common side effects of Relenza are:

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

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.

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).

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.

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.

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.

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.

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.

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.

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

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.

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

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.

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.

Relenza isn't available as a generic product yet. So, it might be costly. If cost is a concern, Relenza's manufacturer does offer reimbursement support services. For additional information, visit GlaxoSmithKline's website or call 800-745-2967.

RxAssist is also another resource that lists patient assistance programs for various medications.

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.

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.

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.

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