Favipiravir is approved for manufacture and sale in Japan as an influenza antiviral. It selectively inhibits the RNA polymerase of the influenza virus, an enzyme required for viral replication once human host cells are infected. COVID-19 also uses this enzyme to replicate and is classified into the same type of single-stranded RNA virus as influenza; hence, it is believed that Favipiravir may be effective in treating COVID-19.

Favipiravir is only used when there is an outbreak of novel or re-emerging influenza virus infections in which other influenza antiviral drugs are either not effective or insufficiently effective. Its production and distribution is at the discretion of Japan’s Health, Labor and Welfare Ministry, so has never been distributed in the market and is not available at hospitals and pharmacies in Japan or overseas.

Pharmacology

Favipiravir is a new antiviral drug against influenza. It is metabolized into favipiravir ribosyl triphosphate (favipiravir RTP) by an intracellular enzyme, and favipiravir RTP selectively inhibits RNA polymerase (RNA-dependent RNA polymerase) of the influenza virus, preventing replication of the influenza virus. It is a drug with a mechanism of action different from that of the existing influenza antiviral drugs and effective against all types and sub-types of human influenza A, B, and C viruses in vitro, showing a wide range of anti-viral activity against various influenza virus strains including avian and swine viruses.

Treatment of novel or re-emerging pandemic influenza virus infections (limited to cases in which other influenza antiviral drugs are ineffective or not sufficiently effective).

The usual adult dosage is 1600 mg of Favipiravir administered orally twice daily on Day 1, followed by 600 mg orally twice daily from Day 2 to Day 5 or as directed by physicians. The total treatment duration should be 5 days.

Favipiravir is contraindicated for pregnant women and women who may possibly be pregnant.

Most common side effects are Diarrhea and increase of blood uric acid levels.

Overdose Effects

In animal studies, decreased RBC production,and increases in liver function parameters such as AST, ALP, ALT and total bilirubin, and increased vacuolization in hepatocytes. Toxicity information regarding Favipiravir in humans is not readily available.

Favipiravir should not be given in pregnant women, requirement of the confirmation of non-pregnancy in women of childbearing potential before use, thorough contraception measures from the start of the treatment to 7 days after the end of the treatment. Caution should be taken for Hepatic and renal impaired patient or use Favipiravir as per the direction of registered Physician

Use in Special Populations

This drug is only approved as an experimental drug and still a lot of studies is needed about it’s efficacy and also toxic reactions and use in children.

Pregnancy & Lactation

Favipiravir may cause delayed development or death of embryos during the early stage of pregnancy. Should not be given during pregnancy.