Zanamivir: uses, dosing, side effects & brands
Zanamivir is a medicine sold in the U.S. under one brand, for human influenza. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Treats
- Human Influenza
- Available as
- Powder
- Sold as
- Relenza
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
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How zanamivir is dosed
From the FDA label for Relenza (application NDA021036). Other zanamivir products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Indication Dose Treatment of Influenza ( 2.2 ) 10 mg twice daily for 5 days Prophylaxis: ( 2.3 ) Household Setting 10 mg once daily for 10 days Community Outbreaks 10 mg once daily for 28 days Note: The 10-mg dose is provided by 2 inhalations (one 5-mg blister per inhalation). ( 2.1 ) 2.1 Dosing Considerations • RELENZA is for administration to the respiratory tract by oral inhalation only , using the DISKHALER device provided [see Warnings and Precautions ( 5.6 )] . • The 10-mg dose is provided by 2 inhalations (one 5-mg blister per inhalation). • Patients should be instructed in the use of the delivery system. Instructions should include a demonstration whenever possible. If RELENZA is prescribed for children, it should be used only under adult supervision and instruction, and the supervising adult should first be instructed by a healthcare professional [see Patient Counseling Information ( 17 )] . • Patients scheduled to use an inhaled bronchodilator at the same time as RELENZA should use their bronchodilator before taking RELENZA [see Patient Counseling Information ( 17 )] . 2.2 Treatment of Influenza • The recommended dose of RELENZA for treatment of influenza in adults and pediatric patients aged 7 years and older is 10 mg twice daily (approximately 12 hours apart) for 5 days. • Two doses should be taken on the first day of treatment whenever possible provided there is…
Zanamivir side effects
The following adverse reactions are discussed in greater detail in other sections of the labeling: • Bronchospasm [see Warnings and Precautions ( 5.1 )] . • Safety information in patients with underlying airways disease [see Warnings and Precautions ( 5.1 )]. • Allergic-like reactions [see Warnings and Precautions ( 5.2 )] . The most common adverse events reported in greater than 1.5% of subjects treated with RELENZA and more commonly than in subjects treated with placebo are: • Treatment Trials – sinusitis, dizziness. ( 6.1 ) • Prophylaxis Trials – fever and/or chills, arthralgia, and articular rheumatism. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact GlaxoSmithKline at 1-888-825-5249 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. The placebo used in clinical trials consisted of inhaled lactose powder, which is also the vehicle for the active drug; therefore, some adverse events occurring at similar frequencies in different treatment groups could be related to lactose vehicle inhalation. Treatment of Influenza Clinical Trials in Adults and Adolescents: Adverse events that…
Who shouldn’t take zanamivir
RELENZA is contraindicated in patients with history of allergic reaction to any ingredient of RELENZA, including milk proteins [see Warnings and Precautions ( 5.2 ), Description ( 11 )] . Do not use in patients with history of allergic reaction to any ingredient of RELENZA, including milk proteins. ( 4 )
Zanamivir drug interactions
The concurrent use of RELENZA with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of potential interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of RELENZA, unless medically indicated. The concern about possible interference arises from the potential for antiviral drugs to inhibit replication of live vaccine virus. Trivalent inactivated influenza vaccine can be administered at any time relative to use of RELENZA [see Microbiology ( 12.4 )] . Live attenuated influenza vaccine, intranasal ( 7 ): • Do not administer until 48 hours following cessation of RELENZA. • Do not administer RELENZA until 2 weeks following administration of the live attenuated influenza vaccine, unless medically indicated.
Every zanamivir product we track (1)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
Only one: Relenza.
Zanamivir and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for zanamivir: levels in milk, effects in breastfed infants, and the drugs it would consider insteadNo information is available on the use of zanamivir during breastfeeding. One group of authors estimated that an exclusively breastfed 5 kg infant would receive about 0.075 mg daily in breastmilk after an inhaled maternal dose of 10 mg, which is less than 1% of the dose in older children. In addition, because zanamivir is poorly absorbed orally, it is not likely to reach the bloodstream of the infant in clinically important amounts.
National Institute of Child Health and Human Development, record revised April 19, 2021. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about zanamivir
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 412 reports naming zanamivir, and the FDA flagged 97% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- pneumonia32 reports
- acute respiratory distress syndrome30 reports
- respiratory failure27 reports
- pathogen resistance23 reports
- pyrexia23 reports
- cholestasis19 reports
- dyspnoea19 reports
- hepatic failure19 reports
Read these as a signal, not a rate. A report does not mean zanamivir caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 26, 2026.
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Frequently asked questions
What is zanamivir?
Relenza (Zanamivir) is a medication used to treat Human Influenza.
Can you take zanamivir with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run zanamivir against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What forms does zanamivir come in?
Across the brands we track, zanamivir is currently marketed as powder, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic zanamivir?
We do not currently list a generic-labelled zanamivir product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Zanamivir: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/zanamivir
- MLA
- “Zanamivir: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/zanamivir.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for zanamivir on DailyMed (NIH) ↗.