Which antiviral medication is used specifically to treat active influenza?

Oseltamivir phosphate is an antiviral medication specifically designed to treat active influenza, particularly types A and B. It works by inhibiting the enzyme neuraminidase, which is essential for the influenza virus to replicate and spread within the body. By blocking this enzyme, oseltamivir helps to prevent the virus from being released from infected cells, thereby reducing the severity and duration of flu symptoms when initiated early in the course of the illness.

Other antiviral agents mentioned are not effective against influenza. Lamivudine primarily targets certain HIV strains and hepatitis B virus but has no activity against influenza. Tenofovir is also an antiviral medication, primarily used against HIV and hepatitis B infections, but it is not indicated for treating influenza. Acyclovir is effective against herpesviruses but does not work against influenza viruses. The specificity of oseltamivir as a neuraminidase inhibitor makes it the preferred choice for actively managing influenza infections.