Baloxavir is primarily used as an antiviral medication for the treatment of influenza in individuals aged 12 years and older who have been symptomatic for no more than 48 hours. It works by inhibiting the cap-dependent endonuclease activity of the influenza virus polymerase, effectively stopping viral replication. This makes it a valuable option for reducing the duration and severity of flu symptoms. Additionally, it is used for post-exposure prophylaxis to prevent influenza in individuals who have been in close contact with someone diagnosed with the flu. Its single-dose administration offers a convenient treatment option compared to other antiviral medications that require multiple doses over several days.