Zanamivir

Zanamivir is an antiviral medication used to treat and prevent influenza. It is a neuraminidase inhibitor administered as an inhaled dry powder (Diskhaler) under the brand name Relenza. By blocking the influenza neuraminidase enzyme, zanamivir prevents the release and spread of new viral particles from infected cells in the respiratory tract.

Medical uses include treatment of uncomplicated influenza A and B in patients who start therapy within 48 hours of symptom onset, and chemoprophylaxis to reduce the risk of influenza during outbreaks in individuals at risk of complications. In many labeling guidelines, treatment is for patients typically 7 years and older, while prophylaxis is approved for those 5 years and older.

Administration and dosing involve inhalation of 10 mg (two 5 mg inhalations) taken twice daily for 5 days for treatment, or once daily for 10 days for prophylaxis. Because zanamivir is inhaled, it is not suitable for people who have severe asthma, COPD, or other conditions that markedly impair breathing or who cannot use inhalers effectively. Caution is advised in individuals with underlying airway disease, due to the risk of bronchospasm and wheezing.

Common adverse effects include cough, throat irritation, nasal congestion, and headache. Less frequent effects may include shortness of breath, dizziness, or hypersensitivity reactions. Zanamivir is poorly absorbed systemically, being excreted largely unchanged in urine; the clinical significance of systemic exposure is limited.

Resistance has been reported, though it remains relatively uncommon. Pregnancy data are limited; treatment decisions should weigh potential benefits against unknown risks. Zanamivir is a targeted option for influenza management when appropriate inhalation therapy is feasible.