What is favipiravir? Is the Japanese flu drug effective against coronavirus?
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What is favipiravir?
Favipiravir (Avigan) is a drug approved in Japan and China for influenza, or seasonal flu, but used experimentally for novel coronavirus disease COVID-19. Favipiravir is an antiviral in the viral RNA polymerase inhibitor class and is a prodrug, meaning it is converted into its active form in the human body.
The Japanese company Fujifilm Toyama Chemical, which developed favipiravir, was praised by Chinese specialists following clinical trials.
Early results of clinical research in China suggest that favipiravir has a modest antiviral effect in treating COVID-19 (reference 1).
Who is favipiravir recommended for in Turkey?
According to the COVID-19 Adult Patient Management and Treatment Guideline prepared by the Republic of Turkey's Ministry of Health, favipiravir is included in
- "Outpatient Treatment Recommendations for Asymptomatic Confirmed COVID-19 Cases"; however, we see that it is not recommended as the first choice for outpatients, where the preferred first choice is more often Plaquenil.
- Favipiravir is also included in "Treatment Recommendations for Probable/Confirmed COVID-19 Cases Without Complications or With Mild-to-Moderate Pneumonia Followed as Outpatients."
- It is also used for COVID-19 patients who are hospitalized.
In Turkey, the active ingredient favipiravir is manufactured under the brand names Convolyn (Santa Farma), Favicovir (Atabay), Favimol (Neutec), Favira (Novelfarma), Loqular (World Medicine), Raviran (Koçak Farma).
Favipiravir studies for COVID-19 treatment
A statement reported in the Japanese press on 13 March said that Chinese medical officials had described a drug used by Japan to treat new influenza cases as effective in coronavirus patients.
Zhang Xinmin, an official at China's Ministry of Science and Technology, said favipiravir, developed by a Fujifilm subsidiary, had produced notable results in clinical studies involving 340 patients in Wuhan and Shenzhen.
The statement said patients taking favipiravir tested negative for the virus a median of 4 days after their positive coronavirus test, compared with a median of 11 days for those not treated with the drug.
Radiological images also reportedly showed lung improvement in approximately 91% of favipiravir-treated patients, compared with 62% of those followed without the drug.
In 2014, Fujifilm Toyama Chemical, the developer of the drug also known as Avigan, declined to comment on the claims. Avigan is favipiravir's brand name in Japan.
The company's shares rose after Zhang's comments on 18 March and closed the morning at 5,207 yen, up 14.7%.
Doctors in Japan predict that the drug could benefit coronavirus patients with mild-to-moderate symptoms.
However, a Japanese health ministry source suggested that the drug was ineffective in people with more severe symptoms. Mainichi Shimbun reported, "We gave Avigan to 70 to 80 people, but it does not seem to work as well once the virus has already multiplied". This is actually a known characteristic of antivirals commonly used for viral respiratory illnesses, such as oseltamivir: the earlier they are taken, the more effective they are.
The same limitations were identified in studies involving coronavirus patients receiving a combination of lopinavir and ritonavir, antiretroviral drugs developed for HIV, as noted by the added source.
In 2016, the Japanese government provided favipiravir as emergency aid against the Ebola outbreak in Guinea.
Because favipiravir was originally developed for influenza, it will require government approval for full-scale use in COVID-19 patients.
What does the Infectious Diseases Society of America guideline say about favipiravir?
The section on favipiravir use in COVID-19 in the Infectious Diseases Society of America (IDSA) guideline, whose latest version was published on 4 September, reads as follows:
In terms of its potential role in COVID-19, favipiravir shows activity in vitro against SARS-CoV-2. However, it is unclear whether sufficient drug levels can be reached in vivo, in the body, to suppress SARS-CoV-2. Small clinical trials have tested this drug in people with COVID-19. In a nonrandomized, open-label study in China, favipiravir was associated with a shorter viral clearance time and greater improvement on chest imaging than lopinavir / ritonavir. However, the study was small and nonrandomized, so it was not possible to conclude that favipiravir was effective for COVID-19 treatment. A randomized, open-label study compared favipiravir with umifenovir, an antiviral approved in Russia and China, in people with COVID-19. Clinical recovery rates on the seventh day did not differ significantly between the two groups. Favipiravir appeared to have an effect in the subgroup without critical illness, but more data are needed. Another exploratory clinical trial in China randomized 30 adults hospitalized with COVID-19 to baloxavir marboxil, favipiravir or a control group. Favipiravir, or baloxivir, had no clear effect on viral clearance. Clinical trials evaluating favipiravir for COVID-19 treatment are ongoing (reference 3).
How is Favicovir used, and what is the dose?
- Day 1: 1600 mg (8 tablets) in the morning and 1600 mg (8 tablets) in the evening, twice daily.
- Days 2-5: 600 mg (3 tablets) in the morning and 600 mg (3 tablets) in the evening, twice daily.
The duration of use is 5 days. In oral cases, it may extend to 10 days.
For oral use, taken with or without food.
Caution: Because early embryonic deaths and teratogenicity were observed in animal studies, favipiravir must not be used in women who are pregnant or suspected to be pregnant. Favipiravir is distributed in sperm. When this medicinal product is given to male patients, they should be informed of all risks and instructed to use the most effective contraceptive method during treatment and for 7 days after it ends; men should use condoms. Patients should also be told not to have sexual intercourse with pregnant women.
What are Favicovir's adverse effects?
Favipiravir was not administered at the approved dose in clinical trials. In safety assessments of Japanese clinical trials and the global phase III trial, conducted at doses lower than the approved dose, adverse reactions were observed in 100 of 501 patients (19.96%). Major adverse reactions were increased blood uric acid in 24 patients (4.79%), diarrhea in 24 (4.79%), decreased neutrophils in 9 (1.80%), increased AST (GOT) in 9 (1.80%), and increased ALT (GPT) in 8 (1.60%).
Note: Favipiravir has no prophylactic, or preventive, effect against the novel coronavirus; it is only one of the agents being tested for treatment.
RELATED TOPICS
Sources
Discovering drugs to treat coronavirus disease 2019 (COVID-19).
Drug Discoveries & Therapeutic, 2020 Volume 14 Issue
2. Justin McCurry
Japanese flu drug 'clearly effective' in treating coronavirus, says China.
theguardian.com - 18 March 2020
3. Infectious Diseases Society of America Guidelines on the Treatment and Management of Patients with COVID-19
Published by IDSA on 4/11/2020. Last updated, 9/25/2020
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