Zanamivir (Relenza) dosage: inhaler dose for treatment and prevention

Relenza dose and availability

The usual Relenza (zanamivir) dose for treating flu is 10 mg, or two inhalations, twice a day for 5 days. It is approved for treatment in ages 7 and older. For prevention after exposure, the dose is 10 mg once daily for 10 days in a household setting or 28 days in a community outbreak, starting at age 5 and older for household use. Treatment works best when started early, so contact a prescriber as soon as symptoms begin.

Relenza is a prescription-only inhaled powder, and not every pharmacy keeps it on the shelf. Call ahead before you go, and ask your pharmacist whether it is in stock or can be ordered. If your pharmacy cannot get it quickly, a prescriber can talk with you about other antivirals, such as oral Tamiflu (oseltamivir) or Xofluza (baloxavir). CDC does not recommend zanamivir for people with underlying airways disease such as asthma or COPD, so tell your prescriber about any lung condition before you fill the prescription. You can also get flu treatment online without leaving home.

What is the Relenza dose?

Zanamivir is a prescription antiviral drug used to treat influenza. Unlike oral antivirals, zanamivir is inhaled directly into the lungs, targeting the respiratory tract where flu viruses thrive. Proper dosing is crucial for effectiveness and safety. This guide breaks down how much zanamivir to take, when to take it, and how to use it correctly.

Relenza dosage chart

Zanamivir dosage by condition

Treatment of influenza

The recommended dose for treating influenza in adults and children aged 7 years and older is 10 mg (two inhalations) twice daily for five days. Starting treatment within 48 hours of symptom onset is essential for maximum benefit. The inhalations are administered using the Diskhaler device, which delivers the medication directly to the lungs.

Prophylaxis (prevention) of influenza

For preventing flu after exposure, the dose is typically 10 mg once daily for 10 days when someone in your household has the flu. This applies to adults and children aged 5 years and older. During a community outbreak, the labeled dose is 10 mg once daily for 28 days in adults and adolescents. Prophylaxis is especially recommended for individuals at high risk of complications or those who have been in close contact with infected persons.

What is the typical zanamivir dose for adults?

Adults usually take zanamivir as two inhalations (totaling 10 mg) twice daily to treat an active influenza infection. For prevention, the standard dose is two inhalations once daily. Treatment lasts five days, while prevention lasts 10 days in a household setting and 28 days in a community outbreak.

How to use the Relenza Diskhaler

Relenza is inhaled through the mouth using only the Diskhaler device that comes in the box. Each dose is two inhalations (10 mg total). The powder must never be mixed into liquid or put in a nebulizer (a machine that turns liquid medicine into mist). In one reported hospital case, the lactose in the powder blocked the equipment, and the case was fatal. If you also use a rescue inhaler (a bronchodilator, which opens the airways), take it before Relenza.

Follow the illustrated leaflet in your box, and ask your pharmacist to demonstrate the device the first time. The basic steps are:

1. Load the medicine disk into the Diskhaler as shown in the leaflet.
2. Pierce the blister (a tiny sealed pocket holding the powder) using the device's built-in piercing step.
3. Breathe out fully, turned away from the mouthpiece.
4. Seal your lips around the mouthpiece and breathe in steadily and deeply.
5. Hold your breath as long as is comfortable, then breathe out slowly.
6. Repeat to complete the second inhalation of the dose.

Children should use Relenza only with an adult who has first been taught how by a healthcare professional. Stop using it and get emergency care if you develop wheezing or trouble breathing. The label does not recommend Relenza for people with asthma or COPD, because of the risk of serious bronchospasm (sudden tightening of the airways).

Relenza for kids: ages 7+ (treatment) and 5+ (prevention)

Children aged 7 years and older can use zanamivir for treatment at the same dose as adults: 10 mg twice daily for five days. For prevention, children 5 years and older may take 10 mg once daily. Zanamivir is not approved for children younger than 5 years due to safety concerns.

What to do if you miss a dose of zanamivir?

Take the missed dose as soon as you remember. If it is almost time for your next scheduled dose, skip the missed dose instead. Do not double up to make up for a missed dose. Maintaining consistent dosing is important for the medication to work effectively against the flu virus.

How to adjust your zanamivir dose for certain medical conditions

Who should not use Relenza: asthma and COPD

Zanamivir is inhaled directly into the lungs, which may cause bronchospasm in patients with underlying respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD). CDC does not recommend zanamivir for people with underlying airways disease such as asthma or COPD. In these cases, doctors may recommend alternative treatments. Always consult your healthcare provider before using zanamivir if you have lung disease.

Kidney problems

Zanamivir is primarily eliminated through the kidneys, so people with severe kidney problems should tell their healthcare provider before starting it. The Relenza label does not call for a dose adjustment for inhaled zanamivir in kidney impairment, but tell your prescriber about any kidney condition. The right plan depends on how well your kidneys work and whether you are using Relenza for treatment (five days) or prevention (10 or 28 days).

Mention any kidney condition when the prescription is written, and ask your pharmacist to review it before you fill it. Your doctor can help determine the safest approach.

Prevention dosing: household vs community exposure

For flu prevention, the dose is the same in both settings, 10 mg (two inhalations) once daily, but the length of use differs. A household exposure calls for 10 days. A community outbreak calls for 28 days. Which one applies depends on how you were exposed.

• Household exposure: 10 mg once daily for 10 days. The label covers adults and children aged 5 years and older. There are no effectiveness data when prophylaxis (preventive treatment) starts more than 1.5 days after the sick person's symptoms began.
• Community outbreak: 10 mg once daily for 28 days. The label covers adults and adolescents. There are no effectiveness data when it starts more than 5 days after the outbreak was identified.

Starting late means the label offers no evidence the drug will protect you, so contact a prescriber as soon as you learn of an exposure. CDC does not recommend zanamivir for people with underlying airways disease such as asthma or COPD (chronic obstructive pulmonary disease), so ask about other options if that applies to you. Confirm your exact dose and duration against the prescribing information or with your pharmacist.

Relenza vs Tamiflu and Xofluza

Tamiflu, Relenza, and Xofluza all treat influenza A and B, and CDC points different people toward each one. Relenza is the inhaled option, and it fits a narrower group than the other two.

• Tamiflu (oseltamivir, also sold as a generic): This oral capsule or liquid is taken twice a day for 5 days. CDC recommends it for hospitalized patients with flu. It is also the option CDC and the American Academy of Pediatrics support for infants, including those under 14 days old.
• Relenza (zanamivir): This is an inhaled powder taken twice a day for 5 days, for ages 7 and older for treatment and 5 and older for prevention. CDC does not recommend it for people with underlying airways disease such as asthma or COPD. It is also not routinely recommended for hospitalized patients, because there is not enough data showing benefit.
• Xofluza (baloxavir): This oral drug is a single dose for treatment and works differently from the other two. It is approved for prevention in ages 5 and older. CDC does not recommend it alone for severely immunosuppressed people, and it is not routinely recommended for hospitalized patients.

A prescriber weighs age, weight, kidney function, other conditions, and possible drug interactions when choosing among them. For people who are not at higher risk, CDC says treatment can be considered if it starts within two days of illness onset. Because a prescriber weighs possible drug interactions when choosing among these options, bring a full list of your medicines to the visit so they can review zanamivir interactions with you. If you are comparing the oral option, the Tamiflu dosage guide explains how much to take and when. Tamiflu, Relenza, and Xofluza are all FDA-approved flu antivirals, and CDC points different people toward each one.

Zanamivir overdose and warnings

Overdose with zanamivir is rare due to its inhalation route. However, taking more than the recommended dose may increase the risk of side effects such as cough, wheezing, or throat irritation. If an overdose is suspected, seek medical attention immediately. Always use the Diskhaler device as instructed to avoid dosing errors. Wheezing or trouble breathing are key warning signs to watch for among zanamivir side effects, and if they appear, stop the medicine and get emergency care right away.

Tips for taking zanamivir safely

• Use the Diskhaler device exactly as prescribed to ensure proper delivery of the medication.
• Do not use zanamivir if you have underlying airways disease such as asthma or COPD. Ask your doctor about other options.
• Start treatment as soon as flu symptoms appear for the best results.
• Inform your healthcare provider about all other medications and health conditions.
• If you experience breathing difficulties after inhaling zanamivir, stop use and seek emergency care.

Frequently Asked Questions

Can I take zanamivir if I have asthma?

No. Zanamivir can cause bronchospasm, so CDC does not recommend zanamivir for people with underlying airways disease such as asthma or COPD. If you have lung disease, always consult your healthcare provider before using it.

How soon after flu symptoms start should I take zanamivir?

For best results, start zanamivir treatment within 48 hours of symptom onset.

Is zanamivir safe for children?

Zanamivir is approved for children aged 7 years and older for treatment and 5 years and older for prevention. It is not recommended for younger children.

What should I do if I miss a dose?

Take the missed dose as soon as you remember, unless it is close to the next dose. Do not double up doses.

Can I get a prescription for zanamivir through telehealth?

Doctronic offers telehealth consultations where licensed doctors can evaluate your symptoms and prescribe a flu antiviral if appropriate. Ask whether Relenza or an oral option such as Tamiflu or Xofluza fits you.

The Bottom Line

Adults take zanamivir (Relenza) as 10 mg, or two inhalations, twice a day for 5 days to treat flu. For prevention, the dose is 10 mg once daily for 10 days after household exposure or 28 days during a community outbreak. Treatment works best when started early. CDC does not recommend zanamivir for people with asthma or COPD.