Ribavirin (brand names: Copegus, Rebetol, Ribasphere, Vilona and Virazole) is an anti-viral drug indicated for severe RSV infection (individually), hepatitis C infection (used in conjunction with peginterferon alfa-2b or peginterferon alfa-2a) and other viral infections. Ribavirin is a prodrug, which when metabolized resembles purine RNA nucleotides. In this form it interferes with RNA metabolism required for viral replication. How it exactly affects viral replication is unknown; many mechanisms have been proposed for this (see Mechanisms of Action, below) but none of these has been proven to date. Multiple mechanisms may be responsible for its actions.