Ribavirin is a guanosine analog used to stop viral RNA synthesis and viral mRNA capping, thus, it is a nucleoside inhibitor,it is an anti-viral drug indicated for severe RSV infection, hepatitis C infection (can be used in conjunction with peginterferon alfa-2b or peginterferon alfa-2a), and some 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 but none of these has been proven to date. Multiple mechanisms may be responsible for its actions.Ribavirin is also a teratogen in some animals species and thus poses a theoretical reproductive risk in humans, remaining a hazard as long as the drug is present, which can be as long as 6 months after a course of the drug has ended.