Multiple antiviral drugs are active against hepatitis B, but only four are currently recommended: entecavir, tenofovir disoproxil fumarate, tenofovir alafenamide, and pegylated interferon-alfa (peginterferon alfa): Adefovir, interferon alfa, lamivudine, and telbivudine have been used but are no longer recommended as first-line treatment because of increased risk of adverse effects and development of drug resistance.