Name one antiviral drug used for chronic hepatitis B.

Tenofovir is an antiviral drug that is commonly used for the treatment of chronic hepatitis B. It is a nucleotide analog that works by inhibiting viral DNA synthesis, leading to a reduction in the replication of the hepatitis B virus (HBV). This makes it effective in managing chronic infections, helping to lower the viral load and potentially leading to improved liver function and decreased risk of liver-related complications.

In contrast, other antiviral agents listed are not typically used for chronic hepatitis B. Acyclovir is primarily effective against herpes simplex virus and some forms of varicella-zoster virus, while oseltamivir is used to treat and prevent influenza virus infections. Ribavirin is primarily used in the treatment of hepatitis C and some viral hemorrhagic fevers, rather than hepatitis B. Thus, Tenofovir is the appropriate choice for patients dealing with chronic hepatitis B infection.