Real-World Effectiveness and Optimal Dosage of Favipiravir for Treatment of COVID-19: Results from a Multicenter Observational Study in Thailand

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.

Automated summary

This retrospective observational study in Thailand found that favipiravir showed promising effectiveness in treating hospitalized COVID-19 patients. Older age, higher baseline NEWS2 score, and lower loading dose of favipiravir were identified as poor prognostic factors for early clinical improvement.