The mechanism of its actions is thought to be related to the selective inhibition of viral RNA-dependent RNA polymerase. Favipiravir is a prodrug that is metabolized to its active form, favipiravir-ribofuranosyl-5'-triphosphate (favipiravir-RTP), available in both oral and intravenous formulations. In 2014, favipiravir was approved in Japan for stockpiling against influenza pandemics. However, favipiravir has not been shown to be effective in primary human airway cells, casting doubt on its efficacy in influenza treatment.
Favipiravir-RTP is a nucleoside analogue. It mimics both guanosine and adenosine for the viral RdRP. Incorporating two such bases in a row stops primer extension, although it is unclear how as of 2013.