Zanamivir is primarily used as an antiviral medication to treat and prevent influenza, particularly influenza A and B. It is administered via inhalation, allowing it to directly target the respiratory tract where the virus replicates. This makes it effective in reducing the severity and duration of flu symptoms when taken within 48 hours of symptom onset. It is also prescribed as a preventive measure for individuals at high risk of complications from the flu, such as those with weakened immune systems or chronic respiratory conditions. Additionally, zanamivir is sometimes used in settings like nursing homes to control flu outbreaks. Its mechanism involves inhibiting the neuraminidase enzyme, which is crucial for the virus's ability to spread to other cells.