Tamiflu (oseltamivir phosphate), Relenza (zanamivir) and Rapivab (peramivir) are the three FDA-approved influenza antiviral drugs recommended by CDC for use against recently circulating influenza viruses.nfluenza can cause different illness patterns, ranging from mild common cold symptoms, to typical flu, to life-threatening pneumonia, bacterial infections and other complications. There are a number of drugs approved by FDA for the treatment and prevention of influenza.