Zanamivir hydrate is primarily used as an antiviral medication to treat and prevent influenza, commonly known as the flu. It is effective against both influenza A and B viruses. The medication works by inhibiting the neuraminidase enzyme, which is essential for the virus to spread within the body. This helps reduce the severity and duration of flu symptoms if taken within 48 hours of symptom onset. It is also used as a preventive measure in individuals who have been exposed to the flu virus, particularly in high-risk groups such as the elderly, immunocompromised individuals, and those with chronic respiratory conditions. Zanamivir hydrate is administered via inhalation, ensuring it directly targets the respiratory tract where the virus replicates. It is not a substitute for the flu vaccine but serves as an additional tool in managing influenza outbreaks.