Real-world Experience with Favipiravir for Treatment of COVID-19 in Thailand: Results from a Multi-center Observational Study

Rattanaumpawan, P.; Jirajariyavej, S.; Lerdlamyong, K.; Palavutitotai, N.; Saiyarin, J.

Background. Favipiravir is a broad-spectrum oral antiviral agent that shows in vitro activity against SARS-CoV-2. Presently, data on the effectiveness and optimal dosage of favipiravir for treating COVID-19 is limited. Methods. 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. Results. Among 247 COVID-19 patients, 63 (23.0%) received [≥]1 dose of favipiravir. Of these, 27.0% required an O2-nasal cannula, 9.5% required non-invasive ventilation and/or high-flow O2-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 O2-supplementation, and 47.2%[0.4%-64.5%] in patients who required O2-supplementation. No life-threatening adverse events were identified. The 28-day mortality rate was 4.8%. Multivariate analysis revealed three poor prognostic factors for Day-7 clinical improvement [odds ratio (95%CI); p-value]: older age [0.94 (0.89 to 0.99); p=0.04], higher baseline NEWS2 score [0.64 (0.47 to 0.88); p=0.006], and lower favipiravir loading dose ([≤]45 mg/kg/day) [0.04 (0.005 to 0.4); p=0.006]. Conclusions. 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.