With inputs from Dr Monica Vasudev

954:  Favipiravir update

• Currently under investigation for use in the treatment of coronavirus disease 2019 (COVID-19)
• Safety and efficacy have not yet been established.
• COVID-19 (off-label use): Oral: Optimal dose and duration are unknown with only limited data available; 1,600 mg twice daily on day 1, followed by 600 mg twice daily for 7 to 14 days.
• Another clinical trial is using a dose of 2.4 g every 8 hours for 2 doses, followed by 1.2 g 8 hours later on day 1, followed by 1.2 g twice daily for a total of 7 to 10 days.
• Favipiraviris an RNA polymerase inhibitor.
• It is available in some Asian countries for treatment of influenza.
• A study of patients with non-severe disease (oxygen saturation >93%) revealed that the use of favipiravir was associated with faster viral clearance (median time to clearance 4 versus 11 days) and more frequent radiographic improvement (in 91% vs. 62% by day 14) compared with lopinavir-ritonavir. However, it must be noted that other therapies were administered in this non-randomized, open-label study, and the results should be interpreted with caution given potential confounders.
• Favipiravir selectively inhibits RNA polymerase, necessary for viral replication.
• Japan has started a phase 3 clinical trial. A phase 2 trial in the US is set to enrol nearly 50 patients with COVID-19, in collaboration with Brigham and Womens Hospital, Massachusetts General Hospital, and the University of Massachusetts Medical School. In India, a phase 3 trial combining the antiviral agents favipiravir and umifenovir started in May 2020.

10. Adverse Reactions

Frequency not defined:

Gastrointestinal: Decreased appetite, diarrhea, nausea, vomiting

Endocrine & metabolic: Hyperuricemia

Hematologic & oncologic: Decreased neutrophils

Hepatic: Hepatic injury, increased serum transaminases

11. Metabolism/Transport Effects: Inhibits CYP2C8 (weak)
12. Drug Interactions

Influenza Virus Vaccine (Live/Attenuated): Antiviral Agents (Influenza A and B) may decrease the therapeutic effect of Influenza Virus Vaccine (Live/Attenuated). Avoid anti-influenza antivirals from 48 hours prior to and ending 2 weeks after live influenza virus vaccine administration. Risk D: Consider therapy modification

Pyrazinamide: Favipiravir may increase the adverse/toxic effect of pyrazinamide. The risk for increased uric acid concentrations may be increased. Risk C: Monitor therapy

Repaglinide: CYP2C8 Inhibitors (Weak) may increase the serum concentration of repaglinide. Risk C: Monitor therapy

13. Reproductive Considerations

Favipiravir is not approved for use in the United States. On the basis of data obtained from animal reproduction studies, its use is contraindicated in females who may become pregnant in countries where it is approved for the treatment of influenza.

Pregnancy status must be evaluated before use in females of reproductive potential. Females of reproductive potential should use effective contraception during therapy and for 1 week after the last favipiravir dose. Additionally, males with female partners of reproductive potential should use effective contraception during therapy and for 1 week after the last dose of favipiravir.

14. Pregnancy Considerations

Favipiravir is not approved for use in the United States. Based on data from animal reproduction studies, its use is contraindicated in pregnant patients in countries where it is available for the treatment of influenza.

The drug is under study for the treatment of COVID-19; however, pregnant patients were not included in the initial clinical trials. The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) have devised an algorithm to assist practitioners in assessing and managing pregnant women with suspected or confirmed COVID-19 (https://www.acog.org/topics/covid-19; https://www.smfm.org/covid19). The CDC has also issued interim guidance for pregnant women who are diagnosed with COVID-19 (https://www.cdc.gov/coronavirus/2019-ncov/hcp/inpatient-obstetric-healthcare-guidance.html).

Data collection to monitor maternal and infant outcomes after exposure to COVID-19 during pregnancy is underway. Healthcare providers should enrol females exposed to COVID-19 during pregnancy in the Organization of Teratology Information Specialists (OTIS) pregnancy registry (877-311-8972; https://mothertobaby.org/join-study/) or the PRIORITY (Pregnancy CoRonavIrus Outcomes RegIsTrY) (415-754-3729, https://priority.ucsf.edu/).

15. Breast-Feeding Considerations

It is not known if favipiravir is present in breast milk.

According to data from animal studies, breastfeeding is contraindicated during favipiravir therapy.

Favipiravir is being investigated for the treatment of COVID-19; however, lactating women were not included in the initial clinical trials. Interim guidance is available from the Centers for Disease Control and Prevention for lactating women who are diagnosed with COVID-19 (https://www.cdc.gov/coronavirus/2019-ncov/hcp/inpatient-obstetric-healthcare-guidance.html). Information related to COVID-19 and breastfeeding is also available from the World Health Organization (https://www.who.int/docs/default-source/maternal-health/faqs-breastfeeding-and-covid-19.pdf?sfvrsn=d839e6c0_1).

[Source: Uptodate; Medscape]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA