Ribavirin is an inhibitor of human immunodeficiency virus reverse transcriptase.

Ribavirin inhibits the human immunodeficiency virus reverse transcriptase in an in vitro reaction. Ribavirin-5'-diphosphate was close to 40% more inhibitory than ribavirin-5'-triphosphate. Unphosphorylated ribavirin had a reduced, but detectable, effect as an inhibitor, compared with the phosphorylated forms. The compounds seem to have a direct effect on the viral polymerase, and no chain termination was observed in the presence of ribavirin-5'-triphosphate. Combination of any of the ribavirin derivatives tested with 3'-azido-3'-deoxythymidine (zidovudine)-5'-triphosphate resulted in an increase of its anti-human immunodeficiency virus reverse transcriptase activity in the in vitro assay.