1.2.2 Ribavirin Ribavirin is a guanosine analogue that inhibits the in vitro replication of a wide range of RNA and DNA viruses1. The mechanism of antiviral activity is not fully defined, although it may involve alteration of cellular nucleotide pools and inhibition of viral RNA synthesis1, 4. Ribavirin monotherapy has little or no effect on the replication of HCV but can result in normalization of serum ALT activity and improvement in liver histology. However, relapse occurs in nearly all patients treated with ribavirin alone1.