Relenza, with the active ingredient zanamivir, is an antiviral medication used in the treatment and prevention of influenza. It belongs to a class of drugs known as neuraminidase inhibitors, which work by blocking the action of viral neuraminidase enzymes. These enzymes are essential for the influenza virus to spread and infect the cells within the respiratory tract. By inhibiting these enzymes, Relenza effectively prevents the flu virus from proliferating, helping to reduce the severity and duration of flu symptoms. It is administered via inhalation, allowing direct delivery to the lungs, where the influenza virus typically infects. Relenza is most effective when taken within the first two days of the onset of flu symptoms and is approved for use in adults and children over the age of 7.