Antiviral medications are a class of drugs that are typically used to prevent or shorten the duration of the influenza virus. They are considered the second line of defense against the flu. Five different antiviral medications are currently approved for use in the United States. They include Tamiflu (oseltamivir), Relenza (zanamivir), Rapivab (Peramivir), amantadine and rimantadine. However, the flu viruses that make people sick are extremely resistant to amantadine and rimantadine, so these two medications are not recommended to prevent or treat influenza at this time.