Real-World Effectiveness and Optimal Dosage of Favipiravir for Treatment of COVID-19: Results from a Multicenter Observational Study in Thailand
Pinyo Rattanaumpawan, Supunnee Jirajariyavej, Kanokorn Lerdlamyong, Nattawan Palavutitotai, Jatuporn Saiyarin
Antibiotics, doi:10.3390/antibiotics11060805
Favipiravir is a broad-spectrum oral antiviral agent that shows in vitro activity against SARS-CoV-2. Presently, data on the real-world effectiveness and optimal dosage of favipiravir for treating COVID-19 are limited. We conducted a retrospective observational study of hospitalized adult patients with COVID-19 at five tertiary care hospitals in Thailand. We reviewed patient charts to obtain all necessary data. Among 247 COVID-19 patients, 63 (23.0%) received ≥1 dose of favipiravir. Of these 63 patients, 61.9% were male with a median age of 48 years (range 22-85 years), 27.0% required an O 2 nasal cannula, 9.5% required non-invasive ventilation and/or high-flow O 2 therapy, and 6.4% required invasive mechanical ventilation and/or ECMO. The median baseline NEWS2 score was 5 (0-16). The Day-7 clinical improvement rate [95%CI] was 66.7% [53.7-78.0%] in all patients, 92.5% [75.7-99.1%] in patients who did not require O 2 supplementation, and 47.2% [0.4-64.5%] in patients who required O 2 supplementation. No life-threatening adverse events were identified. The 28-day mortality rate was 4.8%. A multivariate analysis revealed three poor prognostic factors for Day-7 clinical improvement (odds ratio (95%CI); p-value): older age (0.94 (0.89-0.99); p = 0.04), a higher baseline NEWS2 score (0.64 (0.47-0.88); p = 0.006), and a lower favipiravir loading dose (≤45 mg/kg/day) (0.04 (0.005-0.4); p = 0.006). In conclusion, our study reports the promising effectiveness of favipiravir for treating COVID-19 patients. In addition to older age and a high baseline NEWS2 score, a low loading dose of favipiravir (≤45 mg/kg/day) was also identified as a poor prognostic factor for early clinical improvement. Further studies to explore the optimal dose and the optimal timing of drug initiation for favipiravir should be performed.
Author Contributions: Conceptualization, P.R.; methodology, P.R., investigation, S.J., K.L., N.P. and J.S.; writing-original draft preparation, P.R., S.J., K.L., N.P. and J.S.; writing-review and editing, P.R., funding acquisition, P.R. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Siriraj Research Fund, Grant number (IO) R016333038, Faculty of Medicine Siriraj Hospital, Mahidol University. The APC was funded by Faculty of Medicine Siriraj Hospital, Mahidol University.
Institutional Review Board Statement: The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board of all involved hospitals. The Siriraj IRB approved the protocol on 1 May 2020 (certification of approval number: Si 357/2020). Informed Consent Statement: Written inform consent was waived due to a retrospective study design.
Conflicts of Interest: The authors declare no conflict of interest.
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