Zanamivir
Zanamivir is an antiviral medication classified as a neuraminidase inhibitor, used specifically for the treatment and prevention of influenza A and B virus infections in adults and children. It is administered via oral inhalation using a specialized device (Diskhaler) and works by inhibiting viral replication, thereby reducing the severity and duration of flu symptoms when treatment begins within 48 hours of symptom onset.
Zanamivir is an inhaled antiviral medication used to treat and prevent influenza A and B infections.
Key facts at a glance
- ATC
- J05AH01
- RxNorm
- 69722
- Generic
- Zanamivir
- Class
- atc-j05
- Brands
- Relenza
- Availability
- rx
- Lactation
- unknown
- Routes
- —
- Forms
- inhaler
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
11 groupspregnancy
first trimesteravoid if possible
use only if benefits outweigh potential risks to fetus
regular prenatal care and fetal monitoring
Use with caution and monitor for adverse effects.
pregnancy
second trimesteruse lowest effective dose
use when benefits outweigh risks; influenza can be more severe in pregnant women
standard prenatal monitoring
Use with caution and monitor for adverse effects.
pregnancy
third trimesteruse as needed
recommended if exposed to or infected with influenza; benefits outweigh risks
standard prenatal monitoring
Use with caution and monitor for adverse effects.
lactation
nursing mothersno adjustment needed
use with caution; minimal systemic absorption may result in low milk transfer
monitor infant for any adverse effects
Use with caution and monitor for adverse effects.
pediatric_age
children 5 12 yearsadult dose - 2 inhalations twice daily
approved for treatment and prophylaxis in children 5 years and older
monitor for bronchospasm especially in patients with asthma
pediatric_age
children under 5 yearsnot recommended
not approved for children under 5; limited safety and efficacy data
close monitoring if used off-label
Use with caution and monitor for adverse effects.
geriatric
elderly 65 years and olderno adjustment needed
use standard adult dosing; no dose adjustment required for age alone
monitor for bronchospasm and respiratory function
renal_impairment
mild to moderateno adjustment needed
no dose adjustment required due to minimal systemic absorption
standard monitoring
renal_impairment
severeuse with caution
limited data available; use only if benefits outweigh risks
monitor renal function
Use with caution and monitor for adverse effects.
hepatic_impairment
mild to moderateno adjustment needed
no dose adjustment required; drug is not significantly metabolized by hepatic enzymes
standard monitoring
hepatic_impairment
severeuse with caution
limited data available; use only if benefits outweigh risks
monitor liver function
Use with caution and monitor for adverse effects.
Statistics and clinical data
FDA approval year
FDA approval year for Zanamivir (Relenza)
Drug class
Pharmacological classification
Common uses
Therapeutic indications
Route of administration
Delivery method
Treatment and prevention of uncomplicated influenza A and B virus infections in adults and children aged 5 years and older. It is particularly useful for patients at high risk of complications or those who cannot use other antiviral medications.
Zanamivir inhibits the neuraminidase enzyme on the surface of influenza viruses. Neuraminidase is essential for cleaving sialic acid residues, which allows newly formed viral particles to be released from infected host cells. By blocking this enzyme, the drug prevents viral spread to uninfected cells.
Most effective when started within 48 hours of symptom onset; not a substitute for annual flu vaccination. Should be used with caution in patients with asthma or COPD due to risk of bronchospasm. Common side effects include headache, throat pain, and nasal discomfort. Resistance is uncommon but has been reported.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy