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Zanamivir is a potent and highly selective inhibitor of the influenza A and B virus surface enzyme, neuraminidase. Viral neuraminidase may facilitate access of virus to cell surfaces and aid the release of newly formed virus particles from infected cells, to allow viral infection of other cells. Influenza viral replication is confined to the superficial epithelium of the respiratory tract. The activity of zanamivir is extracellular; it inhibits the release of infective influenza virions from the epithelial cells of the respiratory tract, thereby reducing the propagation of both influenza A and B viruses.


Zanamivir is indicated for treatment of uncomplicated acute illness due to influenza A and B virus in adults and pediatric patients 7 years of age and older, who have been symptomatic for no more than 2 days. (FDA)

Zanamivir is also indicated for the prophylaxis of influenza in patients aged 5 years and older (FDA)

Zanamivir is not a substitute for annual influenza vaccination

[edit] DOSAGE

  • Treatment of influenza: The recommended dose is two oral inhalations (2 x 5 mg) twice daily for five days providing a total daily inhaled dose of 20mg. Treatment should begin as soon as possible after onset of symptoms for maximum benefit, and at the latest should commence within 48 hours of symptom onset.
  • Prophylaxis of influenza: The recommended dose is two inhalations (2 x 5 mg) once daily, providing a total daily inhaled dose of 10mg, for 10 days. This may be increased up to 28 days if the period of exposure risk extends beyond 10 days.


  • Patients with known hypersensitivity to zanamivir


  • Bronchospasm: Serious, sometimes fatal, cases have occurred. Zanamivir is not recommended in individuals with underlying airways disease. Discontinue the drug if bronchospasm or decline in respiratory function develops.
  • Allergic Reactions: Allergic-like reactions, including oropharyngeal edema, serious skin rashes, and anaphylaxis have been reported in postmarketing experience. Discontinue Zanamivir and initiate appropriate treatment if an allergic reaction occurs or is suspected.
  • Neuropsychiatric Events: Patients with influenza receiving neuraminidase inhibitors, particularly pediatric patients, may be at an increased risk of seizures, confusion, or abnormal behavior early in their illness. Monitor for signs of abnormal behavior.


Clinically significant drug interactions are unlikely


  • Pregnancy Category C (US). There are no adequate and well-controlled studies of zanamivir in pregnant women. Zanamivir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus
  • Studies in rats have demonstrated that zanamivir is excreted in milk. However, nursing mothers should be instructed that it is not known whether zanamivir is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Zanamivir is administered to a nursing mother


The most common adverse events reported in >1.5% of patients are: sinusitis, dizziness, fever and/or chills, arthralgia and articular rheumatism