Zanamivir is an antiviral medication primarily used to treat and prevent influenza, commonly known as the flu. It works by inhibiting the enzyme neuraminidase, which is essential for the virus's ability to spread within the body. This helps to reduce the severity and duration of flu symptoms when taken early in the infection. Zanamivir is typically administered via an inhaler, allowing it to act directly in the respiratory tract. It is most effective when used within the first 48 hours of flu symptoms. While it can be beneficial for those at high risk of complications, it is not a substitute for the influenza vaccine.