favipiravir favipiravir favipiravir, sold under the brand name avigan among others, is an antiviral medication used to treat influenza in japan. it is also being studied to treat a number of other viral infections, including sars-cov-2. like the experimental antiviral drugs t-1105 and t-1106, it is a pyrazinecarboxamide derivative. favipiravirclinical datatrade namesavigan (アビガン, abigan), avifavir, areplivir, othersother namest-705, favipira, favilavirroutes ofadministrationby mouthatc codej05ax27 (who) legal statuslegal status in general: ℞ (prescription only) identifiers iupac name 6-fluoro-3-hydroxypyrazine-2-carboxamide cas number259793-96-9pubchem cid492405drugbankdb12466chemspider431002uniiew5gl2x7e0keggd09537chebichebi:134722chemblchembl221722comptox dashboard (epa)dtxsid60948878 chemical and physical dataformulac5h4fn3o2molar mass157.104 g·mol−13d model (jsmol)interactive image smiles c1=c(n=c(c(=o)n1)c(=o)n)f inchi inchi=1s/c5h4fn3o2/c6-2-1-8-5(11)3(9-2)4(7)10/h1h,(h2,7,10)(h,8,11)key:zcgnovwysgbhau-uhfffaoysa-n it is being developed and manufactured by toyama chemical (a subsidiary of fujifilm) and was approved for medical use in japan in 2014. in 2016, fujifilm licensed it to zhejiang hisun pharmaceutical co. it became a generic drug in 2019. medical use favipiravir has been approved to treat influenza in japan. it is, however, only indicated for novel influenza (strains that cause more severe disease) rather than seasonal influenza. as of 2020, the probability of resistance developing appears low. side effects there is evidence that use during pregnancy may result in harm to the baby. teratogenic and embryotoxic effects were shown on four animal species. mechanism of action 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 ribofuranosyl triphosphate, the active form inside the body 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. society and culture legal status the us department of defense developed favipiravir in partnership with medivector, inc. as a broad-spectrum antiviral and sponsored it through fda phase ii and phase iii clinical trials, where it demonstrated safety in humans and efficacy against the influenza virus. despite demonstrating safety in more than 2,000 patients and showing accelerated clearance of influenza virus by 6 to 14 hours in the unpublished phase iii trials, favipiravir remains unapproved in the uk and the usa. in 2014, japan approved favipiravir for treating influenza strains unresponsive to current antivirals. toyama chemical initially hoped that favipiravir would become a new influenza medication that could replace oseltamivir (brand name tamiflu). however, animal experiments show the potential for teratogenic effects, and the approval of production by the ministry of health, labor and welfare was greatly delayed and the production condition is limited only in an emergency in japan. despite limited data on efficacy, as of march 2021 favipiravir is widely prescribed for outpatient treatment of mild to moderate covid-19 in egypt, hungary and serbia. patients are required to sign a consent form before obtaining the drug. brand names favipiravir is sold under the brand names avigan (アビガン, abigan), avifavir, avipiravir, areplivir, fabiflu, favipira, reeqonus, and qifenda. research covid-19